Twin-free YBa2Cu3O7 films on (001) NdGaO3 showing isotropic electrical behaviour

Investigating the epitaxial nature of YBa2Cu3O7 films on NdGaO3 (001) by Rutherford backscattering (RBS) and X-ray diffraction (XRD) texture measurements we find that the films are almost single crystalline, in the sense that the a, b and c axes are uniquely defined with respect to those of NdGaO3. The crystalline perfection is, however, not reflected in the electrical properties of the films. Although we measure a Tc of 89.7 K, we did not observe the expected anisotropy in the resistivity. We interpret this to be due to Ga diffusion from the substrate into the film, which effectively blocks the chain conductivity

Smart Disc - Application in an ASML wafer stepper

High-precision machines typically suffer from small, but annoying, badly damped vibrations. In case such a vibration problem can not be solved passively, a solution may be found in active vibration control. In this respect, research at the Drebbel Institute is aimed at the development of a device called SMART DISC (SD). It is envisioned as an active structural element, consisting of a piezoelectric position actuator co-located with a piezoelectric force sensor, and control and amplifier electronics. As an industrial, three-dimensional test set-up for evaluation of the performance of SD’s, the lens support of an ASML wafer stepper has been chosen. By inserting SD’s in the lens support, and applying Integral Force Feedback control, the relative tilt of the lens relative to the main plate has been reduced by more than a factor 3. The absolute acceleration level of the top of the lens at its dominant resonance frequency has been successfully reduced to less than 10% of the original level

Analyzing Order Throughput Times in a Milkrun Picking System

E-commerce fulfillment competition evolves around cheap, speedy, and time-definite delivery. Milkrun order picking systems have proven to be very successful in providing handling speed for a large, but highly variable, number of orders. In this system, an order picker picks orders that arrive in real time during the picking process; by dynamically changing the stops on the picker’s current picking route. The advantage of milkrun picking is that it reduces order picking set-up time and worker travel time compared to conventional batch picking systems. This paper is the first in studying order throughput times of multi-line orders in a milkrun picking system. We model this system as a cyclic polling system with simultaneous batch arrivals and determine the mean order throughput time. These results allow us to study the effect of different product allocations. For a real world application we show that milkrun order picking reduces the order throughput time significantly compared to conventional batch picking

New SP-values of time and reliability for freight transport in the Netherlands

This paper discusses the methods used in a study on the values of time and reliability in freight transport in the Netherlands. SP surveys were carried out among more than 800 shippers and carriers. A novel feature is that both for the value of time and reliability two additive components are distinguished: a transport cost and a cargo component. Specific instructions were given to make sure that the carriers provide the former and shippers that contract out the latter component. The resulting values that will be used in CBA in The Netherlands are presented and compared against the international literature

In-situ spectroscopy of intrinsic Bi2Te3 topological insulator thin films and impact of extrinsic defects

Combined in-situ x-ray photoemission spectroscopy, scanning tunnelling spectroscopy and angle resolved photoemission spectroscopy of molecular beam epitaxy grown Bi2Te3 on lattice mismatched substrates reveal high quality stoichiometric thin films with topological surface states without a contribution from the bulk bands at the Fermi energy. The absence of bulk states at the Fermi energy is achieved without counter doping. We observe that the surface morphology and electronic band structure of Bi2Te3 are not affected by in-vacuo storage and exposure to oxygen, whereas major changes are observed when exposed to ambient conditions. These films help define a pathway towards intrinsic topological devices.Comment: 8 pages, 5 figure

Cooperative mixing induced surface roughening in bilayer metals: a possible novel surface damage mechanism

Molecular dynamics simulations have been used to study a collective atomic transport phenomenon by repeated Ar$^+$ irradiations in the Ti/Pt interfacial system. The ion-induced injection of surface atoms to the bulk, the ejection of bulk atoms to the top layers together with surface erosion is strongly enhanced by interfacial mixing. This process leads to a dense interfacial material, and broadening of the interface region. The process scales with the relative difference of the atomic masses. We find that surface roughening and interfacial mixing is strongly coupled via an enhanced counterflow material transport normal to the surface which might be a novel surface damage mechanism. This cooperative phenomenon is active when the bilayer system is subjected to a high dose ion irradiation (multiple ion irradiations) and leads to surface cavity growth.Comment: 6 pages, 6 figures. accepted in Nucl. Instrum. Meth.

A Mathematical Model for Supermarket Order Picking

Order picking consists in retrieving products from storage locations to sat- isfy independent orders from multiple customers. It is generally recognized as one of the most significant activities in a warehouse (Koster et al, 2007). In fact, order picking accounts up to 50% (Frazelle, 2001) or even 80% (Van den Berg, 1999) of the total warehouse operating costs. The critical issue in today’s business environ- ment is to simultaneously reduce the cost and increase the speed of order picking. In this paper, we address the order picking process in one of the Portuguese largest companies in the grocery business. This problem was proposed at the 92nd European Study Group with Industry (ESGI92). In this setting, each operator steers a trolley on the shop floor in order to select items for multiple customers. The objective is to improve their grocery e-commerce and bring it up to the level of the best inter- national practices. In particular, the company wants to improve the routing tasks in order to decrease distances. For this purpose, a mathematical model for a faster open shop picking was developed. In this paper, we describe the problem, our proposed solution as well as some preliminary results and conclusions.info:eu-repo/semantics/publishedVersio

Manganese-induced hydroxyl radical formation in rat striatum is not attenuated by dopamine depletion or iron chelation in vivo

The present studies were aimed at investigating the possible roles of dopamine (DA) and iron in production of hydroxyl radicals (.OH) in rat striatum after Mn2+ intoxication. For this purpose, DA depletions were assessed concomitant with in vivo 2,3- and 2,5-dihydroxybenzoic acid (DHBA) formation from the reaction of salicylate with .OH, of which 2,3-DHBA is a nonenzymatic adduct. Following intrastriatal Mn2+ injection, marked 2,3-DHBA increases were observed in a time- and dose-dependent fashion reaching maximum levels at 6-18 h and a plateau beyond 0.4 μmol (fourfold increase). The delayed increase of 2,3-DHBA levels suggests that Mn2+ induces OH formation in the living brain by an indirect process. The early DA depletion (2 h) and relatively late .OH formation (6 h) indicate independent processes by Mn2+. In addition, depletion of DA (about 90%) by reserpine pretreatment did not significantly alter Mn2+-induced 2,3-DHBA formation or the extent of DA depletion, suggesting that DA or DA autoxidation are not participating in Mn2+-induced .OH formation in vivo. Furthermore, Mn2+ injection did not significantly alter the low molecular weight iron pool in striatum, and co-injections of the iron-chelator deferoxamine with Mn2+ into striatum did not significantly attenuate Mn2+-induced 2,3-DHBA formation. These findings suggest no role of chelatable iron in generation of Mn2+-induced .OH, but do not exclude a role for mitochondrial heme-iron or peroxynitrite (Fe-independent) in Mn2+-induced .OH formation

Capacity Analysis of Sequential Zone Picking Systems

This paper develops a capacity model for sequential zone picking systems. These systems are popular internal transport and order-picking systems because of their scalability, flexibility, high-throughput ability, and fit for use for a wide range of products and order profiles. The major disadvantage of such systems is congestion and blocking under heavy use, leading to long order throughput times. To reduce blocking and congestion, most systems use the block-and-recirculate protocol to dynamically manage workload. In this paper, the various elements of the system, such as conveyor lanes and pick zones, are modeled as a multiclass block-and-recirculate queueing network with capacity constraints on subnetworks. Because of this blocking protocol, the stationary distribution of the queueing network is highly intractable. We propose an approximation method based on jumpover blocking. Multiclass jump-over queueing networks admit a product-form stationary distribution and can be efficiently evaluated by mean value analysis and Norton’s theorem. This method can be applied during the design phase of sequential zone picking systems to determine the number of segments, number and length of zones, buffer capacities, and storage allocation of products to zones to meet performance targets. For a wide range of parameters, the results show that the relative error in the system throughput is typically less than 1% compared with simulation