Precision,Local Search and Unimodal Functions

We investigate the effects of precision on the efficiency of various local search algorithms on 1-D unimodal functions. We present a (1+1)-EA with adaptive step size which finds the optimum in O(log n) steps, where n is the number of points used. We then consider binary (base-2) and reflected Gray code representations with single bit mutations. The standard binary method does not guarantee locating the optimum, whereas using the reflected Gray code does so in Θ((log n)²) steps. A(1+1)-EA with a fixed mutation probability distribution is then presented which also runs in O((log n)²). Moreover, a recent result shows that this is optimal (up to some constant scaling factor), in that there exist unimodal functions for which a lower bound of Ω((log n)²) holds regardless of the choice of mutation distribution. For continuous multimodal functions, the algorithm also locates the global optimum in O((log n)²). Finally, we show that it is not possible for a black box algorithm to efficiently optimise unimodal functions for two or more dimensions (in terms of the precision used).     

Manufacturing technologies for miniaturized interference filters

 Miniaturized interference filters were designed and fabricated using two different manufacturing technologies. Applying micromachined ceramic masks during the coating processes interference filters with 1 mm lateral feature size and an alignment accuracy of 50 μm were arranged in an array consisting of three different filters. The filter edge definition obtained by this method was smaller than 50 μm. By applying ion assisted deposition (IAD), a low-temperature coating process, the spectral sensitivity of receiver cells has been modified by coating the cells directly. A combination of coating processes, microlithographic masking procedures, and dry etching technologies made it possible to arrange three different stripe filters with minimum filter features of about 5 μm side by side. The accuracy during mask alignment and the filter edge definition was also within 1 and 2 μm, respectively. Received: 20 March 1999/Accepted: 12 April 1999     

PIN OLEDs — Improved structures and materials to enhance device lifetime

Abstract— Currently, three issues are identified that decide upon the commercial success of organic light‐emitting diodes (OLEDs), both in display and lighting applications: power efficiency, lifetime, and price competitiveness. PIN OLEDs are widely seen as the preferred way to maximize power efficiency. Here, it is reported that this concept also delivers the world longest lifetimes. For a highly efficient deep‐red PIN OLED, a half‐lifetime of 25,000 hours for a starting brightness of 10,000 cd/m² and a minimal voltage increase over lifetime is reported. This value corresponds to more than 1 × 10⁶ hours at 1000 cd/m² using an exponent of n = 1.7, which was measured by driving the OLEDs at different starting luminances. Because there is no initial luminance drop, these PIN OLEDs also exhibit a very high 80% lifetime (>300,000 hours at 1000 cd/m²). New record lifetime values for blue and green will be reported as well. Additionally, further topics that have impact on the production yield and cost such as the newly developed air‐stable organic n‐doping material NDN‐26 and top‐emitting structures will be discussed.     

What is the optimal architecture for visual information routing?

Analyzing the design of networks for visual information routing is an underconstrained problem due to insufficient anatomical and physiological data. We propose here optimality criteria for the design of routing networks. For a very general architecture, we derive the number of routing layers and the fanout that minimize the required neural circuitry. The optimal fanout l is independent of network size, while the number k of layers scales logarithmically (with a prefactor below 1), with the number n of visual resolution units to be routed independently. The results are found to agree with data of the primate visual system.     

Co-oxidation of beta-carotene and canthaxanthine by purified lipoxygenases from soya beans (author's transl)]

Isolation and purification of soya bean lipoxygenase (linoleate: O2 oxidoreductase, EC, 1.13.11.12) on Sephadex G-200, DEAE-cellulose and by isolectric focusing yields two isoenzymes of the L- 2 type (optimum pH 6.5) and two of the L-1 type (optimum pH9.0). Different crude extracts from soya beans as well as the purified L-2 isoenzymes exhibit the same capacity for co-oxidation of beta-carotene and canthaxanthine, when the comparison is based upon equal lipoxygenase activities. In contrast to L-2 the alkaline lipoxygenase L-1 is a poor "carotene oxidase".     

Statistische Beschreibung der Tropfengrößenverteilung bei stationären Zerstäubungsprozessen

The dispersion of spray drops within a two-phase-flow is signified by an deformable phase interface where material properties suddenly change. The process of atomisation could previously only be modelled for standard applications simultaneously coupled with substantial simulations. In this case the process of atomisation is not coupled to the direct numerical simulation (DNS) of the interaction between two liquids. The approach of disintegration is modelled by statistics, describing the probability of generating liquid droplets. Therefore consideration of potential time and length for an intact liquid core are supposed from standard applications [1, 2]. Using this way of describing atomisation is utilised in a CFD-Code and then compared with PDA-measurements to control the process capability of this implementation.

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Zusammenfassung  Zweiphasenströmungen zeichnen sich durch eine bewegliche und deformierbare Phasengrenze aus. An dieser Phasengrenze ändern sich die Stoffeigenschaften sprunghaft. Die Erfassung und Beschreibung dieser Grenzflächeneigenschaften ist sehr aufwendig, so dass die numerische Modellierung von Zerstäubungsprozessen bisher nur für exemplarische Einzelfälle eingesetzt wird. Bei dieser Simulation von Zerstäubungsprozessen ist ein hoher Rechenaufwand gegeben. Der Vorgang des Strahlzerfalls lässt sich, wie im Folgenden dargestellt, mittels Zerfallswahrscheinlichkeiten abbilden. Aerodynamische Grenzflächenbetrachtungen fließen bei dieser Betrachtungsweise nicht in das Modell ein. Bei der Verwendung von Zerfallswahrscheinlichkeiten werden Annahmen zu Länge und Zeit der intakten Strahllänge der flüssigen Phase getroffen, die sich aus ähnlichen technischen Fragestellungen in direkten numerischen Simulationen (DNS) ableiten lassen [1,2]. Durch Anwendung von statistisch erzeugten Tropfenspektren in einem Strömungscode und durch Messung mittels Phasen-Doppler-Anemometrie erfolgt die Überprüfung der Aussagefähigkeit des statistischen Modells.

     

Self-Consistent Quantum Mechanical Monte Carlo MOSFET Device Simulation

We have developed a self-consistent quantum mechanical Monte Carlo device simulator that takes electron transport in quantized states into consideration. Two-dimensional quantized states in MOSFET channels are constructed from one-dimensional solutions of the Schrödinger equation at different positions along the channel, and the Schrödinger and Poisson equations are solved self-consistently in terms of electron concentration and electrostatic potential distribution. The channel electron concentration, velocity and drain currents are calculated with the one particle Monte Carlo approach incorporating the intra-valley acoustic phonon and inter-valley phonon scattering mechanisms. This simulator was applied to a 70 nm n-MOSFET transistor, and we found that current mostly flows through the lowest subband and transport is quasi-ballistic near the source junction. To quantitatively estimate the performance of advanced devices, we have developed an inversion carrier transport simulator based on a full-band model. Our simulation method enables us to evaluate device characteristics and analyze the transport properties of ultra-small MOSFETs.