Slicing from formal semantics: Chisel—a tool for generic program slicing

We describe Chisel, a tool that synthesizes a program slicer directly from a given algebraic specification of a programming language operational semantics \(\mathcal {S}\). \(\mathcal {S}\) is assumed to be a rewriting logic specification, given in Maude, while the program is a ground term of this specification. Chisel takes \(\mathcal {S}\) and synthesizes language constructs, i.e., instructions, that produce features relevant for slicing, e.g., data dependency. We implement syntheses adjusted to each feature as model checking properties over an abstract representation of \(\mathcal {S}\). The syntheses results are used by a traditional interprocedural slicing algorithm that we parameterize by the synthesized language features. We present the tool on two language paradigms: high-level, imperative and low-level, assembly languages. Computing program slices for these languages allows for extracting traceability properties in standard compilation chains and makes our tool fitting for the validation of embedded system designs. Chisel’s slicing benchmark evaluation is based on benchmarks used in avionics.     

Carrier transport in HEMT's analyzed by high-fieldelectroluminescence

The high-field emission of visible light from GaAs and InGaAs high electron mobility transistors (HEMTs) has been used to analyze the hot-electron conduction processes in these devices. Spectral analysis of this electroluminescence has indicated that emission has several components, due to recombination in different layers of the transistor. Analysis of the luminescence provides insights into the vertical distribution of electrons and holes when the transistor is operated at high biases. From the measurements, it seems clear that hot conduction electrons flow both in the conducting channel as well as in the barriers and neighboring quantum wells, and that this dominates the electrical behavior at high drain-source bias voltages     

Transient Analysis of Markovian Queueing Systems and Its Application to Congestion-Control Modeling

In applied queueing theory, it is often important to deal with transient system behavior. Performance evaluation of congestioncontrol mechanisms in a packet-switching network is an excellent example in which there is frequently a strong need to deal with the intrinsic dynamic character of congestion. In that case, the queueing models have to be analyzed for a transient environment. In this paper, we show that such problems can be treated in a uniform way, when the system of coupled differential equations describing the system-state or flow process is solved numerically. For this, the fourth-order RungeKutta procedure allows a good balance between memory requirements, computing time, and accuracy. To illustrate the explanatory power of this kind of transient queueing analysis, three models will be considered: the common-store queueing system showing the priority deadlock, the foreground-background congestion-control mechanism, and a two-level global congestion-control mechanism.     

Radioactivity and heavy metal concentrations in food samples from Rize, Turkey

BACKGROUND: Rize in Turkey was contaminated by the Chernobyl accident in 1986. A comprehensive study was planned and carried out to determine the radioactivity levels and heavy metal concentrations in four food categories collected in Rize in 2008, 2009 and 2010. RESULTS: Tomato showed the highest concentration of ²³⁸U, at 9.43 ± 0.128 Bq kg^?1, whereas the lowest concentration of 0.20 ± 0.02 Bq kg^?1 was measured in aubergine samples. The highest concentration of ²³²Th was measured at 3.22 ± 0.29 Bq kg^?1 in grape samples. ⁴⁰K was found to contribute the highest activity in all the food samples. The highest activity concentration of ¹³⁷Cs was 10.20 ± 4.19 Bq kg^?1, for parsley. The average contribution range of each of the heavy metals to the dietary intake was 0.13–9.14, 0.27–34.63, 0.05–3.62, 0.11–14.97, 0.78–8.51 and 0.01–1.57 mg, respectively, for Mn, Fe, Cu, Zn, Ni and As. CONCLUSION: The range of radioactivity levels in food samples of the present study is of no risk to public health. Heavy metal concentrations of Mn, Fe, Cu, Zn, Ni and As obtained were far below the established values by FAO/WHO limits. Copyright © 2011 Society of Chemical Industry     

Cubic group-III nitride-based nanostructures—basics and applications in optoelectronics

Molecular beam epitaxy (MBE) of cubic group-III nitrides is a direct way to eliminate the polarization effects which inherently limits the performance of optoelectronic devices containing quantum well or quantum dot active regions. In this contribution the latest achievement in the MBE of phase-pure cubic GaN, AlN, InN and their alloys will be reviewed. A new reflected high-energy electron beam (RHEED) control technique enables to carefully adjust stoichiometry and to severely reduce the surface roughness, which is important for any hetero-interface. The structural, optical and electrical properties of cubic nitrides and AlGaN/GaN will be presented. We show that no polarization field exists in cubic nitrides and demonstrate 1.55 μm intersubband absorption in cubic AlN/GaN superlattices. Further the progress towards the development and fabrication of cubic hetero-junction field effect transistors (HFETs) is discussed.     

Insulating substrates for cubic GaN-based HFETs

The growth of cubic group III-nitrides is a direct way to eliminate polarization effects, which inherently limits the fabrication of normally off heterojunction field-effect transistors (HFETs) in the GaN technology. However, for the achievement of electronic devices with cubic nitrides an important precondition is the availability of a high-resistive substrate or GaN buffer layer with zinc-blende crystal structure. We investigated the applicability of carbonized high resistance Si (0 0 1)-substrates and thick conductive free-standing 3C-SiC (1 0 0) substrates with an Ar⁺-ion-damaged surface layer for this purpose and studied the use of carbon-doped GaN buffer layers for electrical insulation. We found that Ar-implantation of 3C-SiC is an appropriate alternative to fabricate insulation layer for cubic GaN (c-GaN) growth and that C-doped GaN buffers introduce non-linear I-V characteristics. The structural properties of c-GaN on Ar-implanted 3C-SiC are comparable to GaN on untreated 3C-SiC whereas on carbonized Si substrates an increase of dislocation density and surface roughness is observed.     

A novel hybrid PSO–GWO algorithm for optimization problems

Engineering with Computers - In this study, we propose a new hybrid algorithm fusing the exploitation ability of the particle swarm optimization (PSO) with the exploration ability of the grey wolf...