Framework for modeling and analysis of distributed problem-solving systems

Petri nets have the basic concepts necessary to model distributed systems with asynchronous processes. Petri nets are not directly applicable to certain kinds of systems like distributed intelligent systems (DISs). These are complex systems where multiple intelligent agents cooperate through communication to achieve the solution to a problem. The paper identifies the limitations of ordinary Petri nets for modeling DISs and proposes extensions. The extended Petri net incorporates colored tokens, inhibition arcs, non-primitive places and transitions, multiple copies of tokens and cumulative places. It is called a distributed problem-solving Petri net. The definitions and analysis techniques are given and illustrated by means of an example.     

Learning basic concepts of telecommunications: An experiment in multimedia and learning

This paper reports on learning as it is related to use of a multimedia-based tutorial. The tutorial is designed to teach basic concepts of telecommunications to University students. The experiment described analyzes test scores of two sets of students, the first group using the aforementioned tutorial and the second learning in a traditional setting. Although learning, in both cases, occurs, there is no significant difference between the amount learned by students in the control group and those in the experimental group.     

Emulsion polymerisation of highly water-insoluble monomers

Contrary to an earlier report, monomers (e.g. p-tert-butylstyrene and octadecyl methacrylate) which are less soluble in water than styrene have been found to polymerise in emulsion using persulphate initiation. At 60°C, the order of the Interval II polymerisation rate of octadecyl methacrylate is 0.48 in persulphate concentration and 0.68 in sodium dodecyl sulphate concentration. The rate is increased by addition of methanol to the aqueous phase. Unlike styrene, p-tert-butylstyrene could not be polymerised in aqueous suspension by persulphate in the absence of emulsifier. High emulsifier-monomer ratios were used in these experiments so that it is possible that mini-emulsion droplets were a significant reaction locus.     

Plasma polymerization of iron pentacarbonyl with C2 hydrocarbons

Iron-containing plasma polymers are deposited from a plasma using iron pentacarbonyl (Fe(CO)₅) plus C₂ hydrocarbons as comonomers and are characterized using a variety of techniques. The plasma polymers are found to contain high proportions of highly dispersed iron oxide as well as lesser quantities of carboxylate and/or ketonate ions and aldehydic and/or ketonic groups. By decreasing the energy per unit mass W/FM part of the iron is deposited in a lower oxidation state complexed to CO and is soluble in organic solvents. The effects of hydrocarbon saturation and of the ratio of hydrocarbon to Fe(CO)₅ are also described and a comparison is made with the product deposited when only Fe(CO)₅ (or Fe(CO)₅ plus H₂) is used as the monomer.     

Structure families and their growth mechanism in silicon carbide

The existence of a number of modifications in silicon carbide having the same periodicity but different stacking sequence is discussed in a modified framework of screw dislocation theory. Accordingly a sequence of structures belonging to different polytype families may occur in the same crystal piece by a succession of operation of Frank's dislocation slip mechanism.     

Temperature-Dependent Thermal Conductivity of Undoped Polycrystalline Silicon Layers

Polycrystalline silicon is used in microelectronic and microelectromechanical devices for which thermal design is important. This work measures the in-plane thermal conductivities of free-standing undoped polycrystalline layers between 20 and 300 K. The layers have a thickness of 1 m, and the measurements are performed using steady-state Joule heating and electrical-resistance thermometry in patterned aluminum microbridges. The layer thermal conductivities are found to depend strongly on the details of the deposition process through the grain size distribution, which is investigated using atomic force microscopy and transmission electron microscopy. The room-temperature thermal conductivity of as-grown polycrystalline silicon is found to be 13.8 W·m^-1·K^-1and that of amorphous recrystallized polycrystalline silicon is 22 W·m^-1·K^-1, which is almost an order of magnitude less than that of single-crystal silicon. The maximum thermal conductivities of both samples occur at higher temperatures than in pure single-crystalline silicon layers of the same thickness. The data are interpreted using the approximate solution to the Boltzmann transport equation in the relaxation time approximation together with Matthiessen's rule. These measurements contribute to the understanding of the relative importance of phonon scattering on grain and layer boundaries in polysilicon films and provide data relevant for the design of micromachined structures.     

Sequestration of Camptothecin,an Anticancer Alkaloid,by Chrysomelid Beetles

Camptothecin (CPT), a monoterpene indole alkaloid, is a potent inhibitor of eukaryotic toposiomerase-I. Several derivatives of CPT are in clinical use against ovarian and lung cancers. CPT has been reported from several plant species belonging to the order Asterids, with the highest concentration in Nothapodytes nimmoniana (family Icacinaceae). In this paper, we report an intriguing observation of chrysomelid beetles (Kanarella unicolor Jacobby) feeding on the leaves of N. nimmoniana without any apparent adverse effect. LC-MS/MS analysis of the beetles indicated that 54.9% of the ingested CPT’s was recovered from the wings, followed by lesser amounts in the head and abdomen. LC-HRMS analysis revealed that most of the CPT in the insect body was in the parental form available in the plants without any major metabolizable products, including sulfated and glucuronilated forms. The mechanism by which the beetles are able to tolerate substantially high levels of CPT in their body tissue is under investigation.     

Piezoelectric based resonant mass sensor using phase measurement

The paper presents design, development and testing of a resonant sensor to measure mass in the range of 0-12 g. The sensor is built using cantilever structure with piezoelectric excitation, sensing and microcontroller based closed loop electronics. The sensor measures the unknown mass by measuring the shift in resonance frequency of the cantilever beam. The shift in resonance frequency for a change in mass is detected by measuring the phase difference between the piezoelectric sensor output and actuator input using microcontroller. The proposed measurement system is simple and accuracy is found to be ±1.2% of full scale deflection.