Scalability and performance of an agent‐based network management middleware

Rapid growth of computer network sizes and uses necessitate analysis of network application middleware in terms of its scalability as well as performance. In this paper we analyze a distributed network management middleware based on agents that can be dispatched to locations where they can execute close to the managed nodes. The described middleware operates between the network protocol layer and the application layer and uses standard TCP protocol and SNMP probes to interface the network. By aggregating requests from many users into a single agent, our system allows multiple managers to probe problem areas with minimal management traffic overhead. We discuss and quantify the benefits of the described middleware by implementing real‐time network managers using our system. The main result of this paper is a comparison of scalability and efficiency of our agent‐based management middleware and traditional SNMP‐based data collection. To this end, we measured traffic in both real and simulated networks. In the latter case, we designed, used and described here a method of separating simulated application flow into separate subflows to simplify design of simulations. Copyright © 2004 John Wiley & Sons, Ltd.     

On reliability of a certain elementary safety system

The paper deals with the determination of reliability of an elementary safety system which consists of two identical elements used simultaneously (hot reserve) whereas for correct system operation is enough when one out of it is good. The operation time is so short that is assumed it is of zero length. Knowing the reliability of element, reliability of system is found.     

Functional Warsaw: A challenge from the past

This article describes the planning concept known as ‘Functional Warsaw’ (Warszawa Funkejonalna) prepared in 1934 by the architects and urban planners Jan Chmielewski and Szymon Syrkus. This planning exercise can be considered both as a most spectacular example of progressive trends in Polish urban planning thought in the inter‐war period, and as an attempt to respond to the challenge created by the widely known ‘Charter of Athens’ regarding the postulates of the functional urban region.

The article is divided into four sections. The first considers the national background in which circumstances conducive to development of urban thought in Poland created favourable conditions for the relatively early practice of regional planning. The next section deals with the international context, the influence of the foreign avant garde movement as represented in CIAM (the International Congresses of Modern Architecture). In the third section, the authors’ model of the functional urbanized region is described; some critical comments are offered. In the last section the impact of Functional Warsaw is considered against the development of spatial planning not only of Warsaw but of the country as well.     

Verallgemeinerung desCoulombschen Grundgesetzes

Übersicht Geschlossene Ausdrücke für die Summe der durch gegenseitige Spiegelung an Kugelflächen entstandenen Ladungen. Kapazität der Systeme zweier Kugeln. Krafteinwirkungen bei Kugeln mit konstanten Potentialen und Ladungen (gleiche und verschiedene Vorzeichen). Elektrostatisches Gleichgewicht.Mit 13 Abbildungen     

Characterization of Terebinth Fruit Oil and Optimization of Acidolysis Reaction with Caprylic and Stearic Acids

Characterization of the fatty acid and triacylglycerol composition of terebinth fruit oil and the synthesis of structured lipids (SL) were performed in this study. Interesterification reaction of terebinth fruits oil (Pistacia terebinthus L.) with caprylic acid (CA) and stearic acid (SA) to produce a SL was performed in n-hexane using immobilized sn-1,3 specific lipase from Mucor miehei. The effect of reaction conditions and relationship among them were analyzed by response surface methodology (RSM) with a four-factors five-level central composite rotatable experimental design. The four major factors chosen were enzyme load (10–30 wt% based on substrates), reaction time (7–18 h), reaction temperature (40–60 °C) and substrate mole ratio (terebinth oil:SA:CA 1:1:1–1:1:3). The best fitting quadratic model was determined by regression and backward elimination. Based on the fitted model, the optimal reaction conditions for the incorporation of CA and SA were found to be temperature 50 °C; time 18 h; enzyme load 30 wt%; substrate ratio 1:1:3. Under these optimum conditions, the incorporation of SA and CA could be obtained as 19 and 14%, respectively.     

Recent applications of particle image velocimetry in aerodynamic research

Particle image velocimetry (PIV) is increasingly used to investigate unsteady velocity fields instantaneously. For the first time the PIV technique allows the recording of a complete velocity field in a plane of the flow within a few microseconds. The PIV technique thereby provides information about unsteady flow fields which is difficult to obtain with other experimental techniques. The short acquisition times and fast availability of data reduce the operational time, and hence cost, in large scale wind tunnels and test facilities.

At DLR a variety of PIV systems for use in industrial wind tunnels has been developed in the past decade. The flexibility of these portable systems is illustrated by presenting several results of recent PIV applications. More recently the original photographic means of PIV image recording has been partially replaced by high resolution electronic imaging which can provide PIV data nearly on-line. Images recorded by either system use the same multiple-pass, cross-correlation analysis software, whose algorithms are briefly described. Several examples of actual applications are given: the flow issuing from a jet nozzle was imaged by a specially developed high-speed video camera at close proximity. A high resolution dual-frame digital camera was applied in the study of helicopter rotor aerodynamics and wake vortex measurements of an airplane model. Further, large image sequences exceeding 100 PIV recordings provided detailed information on the structure of a turbulent boundary layer.     

Polymeric structure of coal. 2. Structure and thermoplasticity of sulphur-rich Raša lignite

The methods of reduction and reductive alkylation with potassium in tetrahydrofuran and sodium in liquid ammonia have been applied to sulphur-rich, highly fluid (in carbonization) Ra?a lignite. The results indicate that solubilization of coal by alkylation of the coal anion formed in liquid ammonia is a clean and defined process. It is concluded that the highly thermoplastic properties of Ra?a coal result mainly from cleavage of CSC(COC) bridges, low contents of OH and lack of SH groups. In contrast to ‘normal’ bituminous coals investigated until now and characterized by wide distribution of the molecular weight of clusters formed on cleavage of ether bridges, about 80% (w/w) of Ra?a lignite is built of units of almost uniform molecular weight (MW 500).     

Photo-oxidation of polystyrene film: 1. Photo-oxidation of polystyrene films with light absorbed by polymer

The photo-oxidation of polystyrene films irradiated with light absorbed by the polymer has been studied. The overall quantum yield of hydroperoxide as well as the relationship between the concentration of acetophenone-type carbonyl products and α,β-enone and diketone products were found. The spatial distribution of the different types of carbonyl products was investigated.