Nonparametric cost and revenue functions under constant economies of scale: an enumeration approach for the single output or input case

This article shows how the linear programs needed to compute cost and revenue functions under constant returns to scale and a single output or input, respectively, can be replaced with a more efficient enumeration algorithm.     

Least-Squares Support Vector Machines for the identification of Wiener–Hammerstein systems

This paper considers the identification of Wiener–Hammerstein systems using Least-Squares Support Vector Machines based models. The power of fully black-box NARX-type models is evaluated and compared with models incorporating information about the structure of the systems. For the NARX models it is shown how to extend the kernel-based estimator to large data sets. For the structured model the emphasis is on preserving the convexity of the estimation problem through a suitable relaxation of the original problem. To develop an empirical understanding of the implications of the different model design choices, all considered models are compared on an artificial system under a number of different experimental conditions. The obtained results are then validated on the Wiener–Hammerstein benchmark data set and the final models are presented. It is illustrated that black-box models are a suitable technique for the identification of Wiener–Hammerstein systems. The incorporation of structural information results in significant improvements in modeling performance.     

Photoluminescent ZnS:Cu phosphor films made with atomic‐layer chemical vapor deposition and thermal evaporation

Photoluminescent (PL) ZnS:Cu thin films were prepared by atomic‐layer chemical vapor deposition (ALCVD) and by thermal evaporation. The deposition, structure, and PL properties of the films were investigated, as well as the effect of heat treatment on photoluminescence.     

Determining emissive dipole orientation in organic light emitting devices by decay time measurement

We present a method to detect anisotropy in the distribution of the transition dipole moment in organic light emitting diodes (OLEDs). The method is based on the dependency of the exciton decay rate on the optical environment and the orientation of the dipole transition moment, also called the Purcell effect. We use this method to demonstrate a preferential orientation of the small molecule emitter Ir(MDQ)₂(acac) in a TPBi matrix. The outcoupling improvement for OLEDs that could be obtained with perfectly oriented transition dipoles is estimated by simulation. For perfectly planar structures this shows an EQE in air of up to 34%.     

Importance of scattering and absorption for the outcoupling efficiency in organic light-emitting devices

The outcoupling of light in organic light-emitting devices is one of the limiting parameters for obtaining a high external efficiency. A simple geometrical model is presented that allows one to estimate the importance of optical parameters such as mirror reflectivity, scattering probability, and device structure. The model allows the derivation of analytical expressions for the outcoupling efficiency in some simplified cases.     

Electric Field‐Induced Oxidation of Ferromagnetic/Ferroelectric Interfaces

Composite multiferroics are a new class of material where magneto‐electric coupling is achieved by creating an interface between a ferromagnetic and a ferroelectric compound. The challenge of understanding the chemical and magnetic properties of such interface is a key to achieve good magneto‐electric coupling. The unique possibilities offered by isotope sensitive techniques are used to selectively investigate the interface's chemistry and magnetism in Fe/BaTiO₃ and Fe/LiNbO₃ systems during the application of an electric field. With a large enough electric field, a strong oxidation of Fe is triggered, which creates a magnetically dead interface. This leads to an irreversible decrease of the magneto‐electric coupling properties. Material parameters are identified that determine under which electric field the interface may be modified. The results are confirmed on the two systems and are expected to be widespread in this new class of hybrid material.     

Sufficient conditions for draft angles on general B-spline surfaces

Many manufacturing processes, e.g. casting, forging, moulding, require that components must have a sufficient draft angle. Ensuring this when using general B-spline surfaces is a difficult task, often requiring iterative modeling. In this paper a theorem is presented that provides sufficient conditions to ensure draft angle on B-spline surfaces. The theorem is used to develop a simple algorithm that was used to add a draft angle to two surfaces.     

Inhibitory effects of novel nucleoside and nucleotide analogues on Epstein-Barr virus replication

Analysis of the mechanistic basis by which sodium-coupled transport systems respond to changes in membrane potential is inherently complex. Algebraic expressions for the primary kinetic parameters (Km and Vmax) consist of multiple terms that encompass most rate constants in the transport cycle. Even for a relatively simple cotransport system such as the Na+/alanine cotransporter in LLC-PK1 cells (1:1 Na+ to substrate coupling, and an ordered binding sequence), the algebraic expressions for Km for either substrate includes ten of the twelve rate constants necessary for modeling the full transport cycle. We show here that the expression of Km of the first-bound substrate (Na+) simplifies markedly if the second-bound substrate (alanine) is held at a low concentration so that its' binding becomes the rate limiting step. Under these conditions, the expression for the KNam includes rate constants for only two steps in the full cycle: (i) binding/dissociation of Na+, and (ii) conformational 'translocation' of the substrate-free protein. The influence of imposed changes in membrane potential on the apparent KNam for the LLC-PK1 alanine cotransporter at low alanine thus provides insight to potential dependence at these sites. The data show no potential dependence for KNam at 5 micron alanine, despite marked potential dependence at 2 mm alanine when the full algebraic expression applies. The results suggest that neither translocation of the substrate-free form of the transporter nor binding/dissociation of extracellular sodium are potential dependent events for this transport system.     

Multicasting optical interconnects using liquid crystal over silicon devices

This work presents the characteristics and expected capabilities of an optical interconnect that uses a diffractive liquid crystal over silicon (LCOS) device as a routing element. Such an interconnect may be used in a neighborhood's optical network to distribute high definition television, thus avoiding an electronic or optical transmitter for each user. The optimal characteristics of the LCOS device are calculated in terms of pixel number and silicon area and found to be feasible with today's technology. Finally, its performance in terms of optical efficiency and number of output ports is evaluated and found suitable for a neighborhood with hundreds of households.