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.     

STABILITY OF COAL WATER PUEL

In this paper, a novel sensor is presented for monitoring the stability of a coal water fuel. This sensor utilizes a non-radioactive electromagnetic source, making it more attractive in comparison to other existing sensors. It utilizes the interaction between the electromagnetic waves and the CVF composition. Two of these interactions are selected, namely, the transmitted and reflected signal, and are used to give an indication on the stability of the CVF. The sensor measures the concentration changes or structural variations in the CVF. Calibration of the sensor is performed, for a given pipe/tube and a given CVF, by changing the concentration of the CVF and recording the transmitted and refelected signals as functions of concentration. These calibration curves are then stored in a microcomputer. At any instant of tine, the CVF stability is measured by comparing the sensor response to the stored curves. This sensor is easy to use and is readily adapted for automation. To demonstrate the applicability of the technique, the sensor response is measured and calibration curves are extracted and presented here. In this paper, four commonly used stability measurement techniques are also discusse     

Interrelations between initial pore structure, morphology and distribution of accumulated deposits, and lifetimes of hydrodemetallisation catalysts

The functioning of commercial HDM catalysts, experiencing conditions of industrial use in residual feedstocks upgrading reactors is analysed, in order to derive the essential physical and chemical processes that determine their deactivation. A mathematical model of this evolution is presented as an attempt to integrate this analysis into computer simulations for improved reliability of lifetimes predictions. A method to obtain accelerated aging data on HDM catalysts at the bench scale is presented, with examples of results. A method is given to combine such results with EPMA analysis of used catalyst pellets in order to determine the Ultimate Storage Capacity intrinsic to the catalyst's pore structure. Selected results of an High Resolution Electron Microscopy study of microtome thin foiled used HDM catalyst pellets are presented: they show for the first time the nature, morphology and structure of metal sulfides deposits at the micropore level, and support the “discrete” mode of deposition theory. Model predictions and experimental deactivation results are compared, and the limitations of the model discussed. Unsolved questions are listed for future research.     

Terabit optical local area networks for multiprocessing systems

The design of a scalable optical local area network formultiprocessing systems is described. Each workstation has aparallel-fiber-ribbon optical link to a centralized complementarymetal-oxide silicon (CMOS) switch core, implemented on a singlecompact printed circuit board (PCB). When the Motorola Optobusfiber technology is used, each workstation has a data bandwidth of 6.4Gbits/s to the core. A centralized switch core interconnecting 32workstations supports a 204-Gbit/s aggregate data bandwidth. Theswitch core is based on a conventional broadcast-and-selectarchitecture, implemented with parallel CMOS integrated circuits(IC's). The switch core scales well; by incorporation of theCMOS optoelectronic IC's with optical input-output, the electricalcore can be reduced to a single-chip optoelectronic IC with terabitcapacities. A prototype of an optoelectronic switch core has been fabricated and is described. The appeal of the architectureincludes its reliance on commercially available parallel-fibertechnology, its reliance on the well-developed markets of local areanetworks and networks of workstations, and its smooth scalability from the electrical to optical domains as technology matures.     

Texture analysis of poly-adenylated mRNA staining following global brain ischemia and reperfusion

Texture analysis provides a means to quantify complex changes in microscope images. We previously showed that cytoplasmic poly-adenylated mRNAs form mRNA granules in post-ischemic neurons and that these granules correlated with protein synthesis inhibition and hence cell death. Here we utilized the texture analysis software MaZda to quantify mRNA granules in photomicrographs of the pyramidal cell layer of rat hippocampal region CA3 around 1 h of reperfusion after 10 min of normothermic global cerebral ischemia. At 1 h reperfusion, we observed variations in the texture of mRNA granules amongst samples that were readily quantified by texture analysis. Individual sample variation was consistent with the interpretation that animal-to-animal variations in mRNA granules reflected the time-course of mRNA granule formation. We also used texture analysis to quantify the effect of cycloheximide, given either before or after brain ischemia, on mRNA granules. If administered before ischemia, cycloheximide inhibited mRNA granule formation, but if administered after ischemia did not prevent mRNA granulation, indicating mRNA granule formation is dependent on dissociation of polysomes. We conclude that texture analysis is an effective means for quantifying the complex morphological changes induced in neurons by brain ischemia and reperfusion.     

Effect of plasma treatment on the surface properties of polydimethylsiloxane

In this work, the analysis of the plasma modification of polydimethylsiloxane (PDMS) substrates was conducted. The influence of the modification onto the changes occurred within the geometrical structure and chemical composition of the surface was analyzed. Due to the study of the atomic force microscopy, it was possible to determine the relationships between the surface development and applied process parameters, defining the conditions facilitating to obtain isotropic or anisotropic orientations of wrinkles. A precise analysis of the chemical composition of the surface, executed before and after the modification processes, enabled to define the changes in their elementary composition. Moreover, the modification influence onto the changes of the contact angle and the surface free energy were also analyzed. So, based on the research it was stated that the increase of value of the surface free energy is proportional to the sp³ phase contents in the DLC coatings. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41635.     

Testbed for a scalable terabit optical local area network

The design of a fiber-optic local area network (LAN) demonstration system is described. A complete LAN system would consist of an array of 16 personal computers (PC's), where each PC has a network interface card (NIC) with a parallel fiber-optic datalink to a centralized optoelectronic switch core. The centralized core switches the data generated by 16 NIC's, up to 128 Gbit/s of bandwidth. The demonstrator is designed to scale to terabits of bandwidth by use of an emerging optoelectronic technology, i.e., integrated complementary metal-oxide semiconductor (CMOS) substrates with vertical-cavity surface-emitting laser (VCSEL) and photodetector optical input and output. A subset of the complete system was constructed and is operational. A prototype NIC card, with Motorola Optobus VCSEL transceivers for the optical datalinks, was constructed and is described. A prototype high-speed bipolar switch core, with statically configurable electrical positive-emitter coupled-logic 16 x 16 crossbar switches, CMOS field-programmable gate arrays, and Motorola Optobus transceivers, was constructed and is described. We successfully demonstrated the transmission of high-speed packetized data from one NIC card, through 10 m of parallel fiber ribbon and the centralized switch core, and back to the NIC. We summarize our experiences on the design and testing of our first demonstration system and our development toward a terabit switch core.     

Bandwidth optimization of optical data links by use of error-control codes

A design approach to optimizing the bandwidth of optical data links while simultaneously decreasing the bit-error rate is proposed. Mathematical analysis indicates that bandwidth gains by factors of 10-60 with power gains of as much as 8.9 dB are possible. To achieve these performance levels requires several innovations. First, conventional forward error-correcting codes cannot be used because of their excessive hardware cost. A reasonably powerful multidimensional parity-based error-control code is proposed and analyzed. These codes offer excellent error detection and moderate error-correction capabilities. Most importantly, they can operate at the fast clock rates that are required. Second, a hybrid automatic-repeat-request protocol is exploited to correct complex error patterns. In thermal-noise-limited systems this unique combination allows the optical clock rate to be increased significantly, thereby resulting in large bandwidth increases. The proposed design approach can be used in optical data links in which propagation delays are moderate and is applicable to fibers that exploit wavelength-division multiplexing or time-division multiplexing, one-dimensional parallel-fiber ribbons, and two-dimensional optical data links that use free space or guided waves. Several design examples are illustrated.