Self-consistent simulation of quantum wires defined by local oxidation of Ga[Al]As heterostructures

We calculate the electronic width of quantum wires as a function of their lithographic width in analogy to experiments performed on nanostructures defined by local oxidation of Ga[Al]As heterostructures. Two--dimensional simulations of two parallel oxide lines on top of a Ga[Al]As heterostructure defining a quantum wire are carried out in the framework of Density Functional Theory in the Local Density Approximation and are found to be in agreement with measurements. Quantitative assessment of the influence of various experimental uncertainties is given. The most influential parameter turns out to be the oxide line depth, followed by its exact shape and the effect of background doping (in decreasing order).Comment: 5 pages, 6 figures; revised figures, clarified tex

Linear Algebraic Calculation of Green's function for Large-Scale Electronic Structure Theory

A linear algebraic method named the shifted conjugate-orthogonal-conjugate-gradient method is introduced for large-scale electronic structure calculation. The method gives an iterative solver algorithm of the Green's function and the density matrix without calculating eigenstates.The problem is reduced to independent linear equations at many energy points and the calculation is actually carried out only for a single energy point. The method is robust against the round-off error and the calculation can reach the machine accuracy. With the observation of residual vectors, the accuracy can be controlled, microscopically, independently for each element of the Green's function, and dynamically, at each step in dynamical simulations. The method is applied to both semiconductor and metal.Comment: 10 pages, 9 figures. To appear in Phys. Rev. B. A PDF file with better graphics is available at http://fujimac.t.u-tokyo.ac.jp/lses

Large-scale electronic structure theory for simulating nanostructure process

Fundamental theories and practical methods for large-scale electronic structure calculations are given, in which the computational cost is proportional to the system size. Accuracy controlling methods for microscopic freedoms are focused on two practical solver methods, Krylov-subspace method and generalized-Wannier-state method. A general theory called the 'multi-solver' scheme is also formulated, as a hybrid between different solver methods. Practical examples are carried out in several insulating and metallic systems with 10^3-10^5 atoms. All the theories provide general guiding principles of constructing an optimal calculation for simulating nanostructure processes, since a nanostructured system consists of several competitive regions, such as bulk and surface regions, and the simulation is designed to reproduce the competition with an optimal computational cost.Comment: 19 pages, 6 figures. To appear in J. Phys. Cond. Matt. A preprint PDF file in better graphics is available at http://fujimac.t.u-tokyo.ac.jp/lses/index_e.htm

The impact of dual sourcing on food supply chain networks: the case of Egyptian strawberries

Supply chain management for fresh produce differs significantly from that of other products. Similarly to other products, fresh produce quality plays a key role in consumer selection behavior. The key difference consists in the fact that, for fresh produce, quality varies over time and it is dramatically affected by storage conditions. Maintaining product quality along the distribution chain is therefore of utmost importance in these chains. Dual sourcing is a common practice adopted in supply chain management for enhancing sourcing flexibility and reducing transportation costs. This work investigates the impact of dual sourcing strategies on quality of fresh fruit traded in international food supply chains. By means of a discrete-event simulation model we investigate dual sourcing in the context of a prototype supply chain that mimics the structure and the operating conditions of a real supply chain

Vooronderzoek evaluatie van automatische nummerherkenning geheimhoudergesprekken advocatuur

Dit is het verslag van een vooronderzoek voor de evaluatie van het systeem van automatische nummerherkenning voor de advocatuur en de afspraken daaromtrent. Het doel van automatische nummerherkenning is te voorkomen dat vertrouwelijke communicatie via telefoon (inclusief SMS) of fax van een advocaat met zijn cliënt die onder een tap is geplaatst, wordt af- en uitgeluisterd door politie en Openbaar Ministerie. Het systeem van nummerherkenning is op 1 mei 2011 in werking getreden

DaVinc3i: Virtualisation Scenarios For Floricultural Trade Networks

The Dutch floricultural industry is generally appreciated for its world leadership; the Netherlands is the trading hub for the European market. There are two trends affecting this position. First, virtualisation of trade and logistics control enabled by technological progress. Second, internationalisation of markets and production reshapes the market in size and distance. To maintain leadership, the Dutch floricultural industry has initiated the Dinalog DaVinc3i project. In this paper we outline the activities we are currently undertaking and some of the outcomes achieved so far. These include 12 commercial scenarios for the future of the industry and specific challenges related to ICT as an enabler of virtualisation in floricultural logistics and trade. Alongside the discussion of these activities and outcomes, we present some thoughts on how to address the challenges based on an (inter)national benchmark carried out as part of the project

Application of stochastic programming to reduce uncertainties in quality-based supply planning of slaughterhouses

To match products of different quality with end market preferences under supply uncertainty, it is crucial to integrate product quality information in logistics decision making. We present a case of this integration in a meat processing company that faces uncertainty in delivered livestock quality. We develop a stochastic programming model that exploits historical product quality delivery data to produce slaughterhouse allocation plans with reduced levels of uncertainty in received livestock quality. The allocation plans generated by this model fulfil demand for multiple quality features at separate slaughterhouses under prescribed service levels while minimizing transportation costs. We test the model on real world problem instances generated from a data set provided by an industrial partner. Results show that historical farmer delivery data can be used to reduce uncertainty in quality of animals to be delivered to slaughterhouses