Effects of sprayer configuration on efficacy for the control of scab on crabapple using electron beam analysis

Foliar diseases like apple scab result in significant economic losses to growers each year. Assessment in past studies involved only macroscopic disease ratings. More complete knowledge of the fate and behavior of fungicide has been needed to reduce pesticide use with less off‐target contamination. Field studies were conducted in a production nursery for over 4 years. A moderately susceptible cultivar of ornamental crabapple, Malus spp. cv “Candied Apple”, was sprayed with a fungicide using two sprayer/nozzle configurations. The fungicide used in this study was Mankocide, combination of Cu(OH)₂ and mancozeb that permitted electron beam analysis (EBA) identification based on the presence of Cu, MN and Zn in the molecule and formulation. EBA was conducted using a cold field emission scanning electron microscopy and energy dispersive x‐ray microanalyzer. Fresh leaf samples were placed on sticky stubs after each fungicide treatment. The presence or absence of fungal conidia and fungicide residue were measured. EBA permitted direct visualization and identification of the pathogens, morphologically, and chemical characterization of fungicide present. EBA was useful to quantify disease control related to fungicide coverage, sprayer configuration and treatment efficacy. SCANNING 31: 24–27, 2009. Published 2009 by Wiley Periodicals, Inc.     

Computational algorithms for networks of queues with rejection blocking

Summary Open, closed and mixed queueing networks with reversible routing, multiple job classes and rejection blocking are investigated. In rejection blocking networks blocking event occurs when upon completion of its service of a particular station's server, a job attempts to proceed to its next station. If, at that moment, its destination station is full, the job is rejected. The job goes back to the server of the source station and immediately receives a new service. This is repeated until the next station releases a job and a place becomes available. In the model jobs may change their class membership and general service time distributions depending on the job class are allowed. Two station types are considered: Either the scheduling discipline is symmetric, in which case the service time distributions are allowed to be general and dependent on the job class or the service time distributions at a station are all identical exponential distributions, in which case more general scheduling disciplines are allowed. An exact product form solution for equilibrium state probabilities is presented. Using the exact product form solution of the equilibrium state distribution, algorithms for computation of performance measures, such as mean number of jobs and throughputs, are derived. The complexity of the algorithms is discussed.     

Performance evaluation of unbalanced flow lines with general distributed processing times, failures and imperfect production

In this paper an analytical approximation for the performance of non-homogenous asynchronous Flow Production Systems (FPSs) with finite buffers is presented. Generally distributed stochastic processing times as well as breakdowns and imperfect production are considered. The procedure explicitly accounts for simultaneous blocking and starving. The approximation is based on the decomposition of an M-station-line into M — 1 two-station-lines which are analyzed with the help of a GI/G/I/N_max queueing model. Numerical comparisons with exact and simulation results for hypothetical as well as for real-life flow-lines indicate that the procedure provides accurate results.     

Hybrid semiconductor electrodes for light-driven photoelectrochemical switches

Hybrid (n-/p-type) semiconductor electrodes represent a viable strategy for fabrication of wavelength-controlled optoelectronic switches. Four hybrid electrodes (BiVO₄/Co₃O₄, BiVO₄/CuO, TiO₂/Co₃O₄, TiO₂/CuO) were prepared in the form of random assemblies of nanocrystalline powders on ITO-glass and the wavelength dependence of their photocurrent response was investigated. The former three electrodes exhibited wavelength-controlled switching of photocurrent direction, whereas the latter one showed exclusively cathodic photocurrents. The prerequisite for the switching effect is that the potentials of the valence and conduction band edges of an n-type component are more positive than those of a p-type one. Further key parameters influencing the photocurrent response are the applied potential and the presence of electron and hole scavengers.     

A modified size effect model for brittle nonmetallic materials

Formulae of both existing size effect models for brittle materials, `effective volume' and `effective surface' were theoretically derived for bar specimens with rectangular and circular cross-sections, for three- and four-point bending load configuration, respectively. Additionally, a modified model called `effective shell model' is introduced. Exemplarily three- and four-point bending tests were performed on bar specimens of different sizes of a leucite reinforced glass ceramic material. The results were analyzed based on the three size effect models. It was found that the defect population of the specimens could be characterized better with the effective surface than with the effective volume model. The new effective shell model improves the statistical reliability even more.     

Über Zeitkonstanten von Kondensatoren

Zusammenfassung Bei hinreichend langer Trocknung und Bernsteinisolation lassen sich mit Luftkondensatoren Zeitkonstanten erreichen, die in der Größenordnung 10⁷ s bzw. 10³ s/pF liegen. Die physikalischen Ursachen der Entladung werden näher untersucht. Praktisch erfolgt die Entladung nur über die Bernsteinisolation; die Leitfähigkeit der Luft ist zu vernachlässigen. Maßgebend für die Entladung ist das Verhältnis Volumen zur Kapazität. Hohe Zeitkonstanten lassen sich erreichen, wenn das Verhältnis Volumen zur Kapazität klein ist. Kondensatoren mit sehr hohen Zeitkonstanten finden ihre Anwendung, z. B. wenn ein aufgeladener Kondensator als Vergleichsspannungsquelle dienen soll, bei der elektrischen Kurzzeitmèssung als Zeittransformator oder zur Messung sehr hoher Widerstände von der Größenordnung 10¹⁰ bis 10¹⁵ nach dem Kondensatorentladungsverfahren. Über eine weitere Anwendung wird demnächst berichtet werden.Die vorliegende Untersuchung wurde von Herrn Prof. Dr.-Ing. E. h. Dr.-Ing. W. Rogowski angeregt, dem ich für seine vielseitige Unterstützung zu großem Dank verpflichtet bin. Der Deutschen Forschungsgemeinschaft danke ich für die Mittel zur Durchführung der Arbeit.     

Optimisation models to enhance resilience in evacuation planning

We argue that the concepts of resilience in engineering science and robustness in mathematical optimisation are strongly related. Using evacuation planning as an example application, we demonstrate optimisation techniques to improve solution resilience. These include a direct modelling of the uncertainty for stochastic or robust optimisation as well as taking multiple objective functions into account.