Heat transfer in forced cooled cables

A calculation method is presented for continuous rating of cable lines. The method takes into account the actual environment conditions, such as different types of soil, change of geometrical disposition, etc. This method is based on the resolution in terms of limit differences. The results for a full-scale experimental installation were used to check the theoretical model. Comparison between the measured and calculated rises showed a difference of 5% in general and a maximum of 7%, which may be considered acceptable for line design     

Comparison-based diagnosis with faulty comparators

The letter deals with a new approach to diagnosis by comparison. A new class of diagnosable systems is introduced: in these systems, units and comparators used in the diagnostic process may fail. Failure of comparators introduces a new condition of test invalidation for comparison. Characterisation theorems and fault identification similarities between different comparison models are presented.     

Error Tolerant DNA Self-Assembly Using ( $hbox{2}k-hbox{1}$)$times$( $hbox{2}k-hbox{1}$) Snake Tile Sets

DNA self-assembly has been advocated as a possible technique for bottom-up manufacturing of scaffolds for computing systems in the nanoscale region. However, self-assembly is affected by different types of errors (such as growth and facet roughening) that severely limit its applicability. Different methods for reducing the error rate of self-assembly using tiles as basic elements have been proposed. A particularly effective method relies on snake tile sets that utilize a square block of even size (i.e., 2k times 2k tiles, k = 2, 3,.. .). In this paper, an odd-sized square block [i.e., (2k -1) times (2k - 1)] is proposed as basis for the snake tile set. Compared with other tile sets, the proposed snake tile sets achieve a considerable reduction in error rate at a very modest reduction in growth rate. Growth and facet roughening errors are considered and analytical results are presented to prove the reduction in error rate compared with an even-sized snake tile set. Simulation results are provided.     

Use of expert systems in the design of thermal equipment and processes

A study has been carried out on the use of knowledge-based computer-aided design methodology for the design of thermal systems. An expert system is developed using a Prolog-based front end, where the design rules, material databases, computational procedures, and the relevant expert knowledge are implemented. A combination of quantitative and heuristic inputs are employed in the design process. The basic approach employs an iterative redesign strategy, starting with an initial design obtained from the available knowledge base, and the design parameters are iteratively varied until the specified design rules and constraints are satisfied. The general approach can be employed for a variety of thermal systems. The application to a practical system is demonstrated by the design of an electrical furnace used in the thermal processing of materials. The results from the numerical simulation and design of this system are presented to indicate the basic features and the versatility of the expert system.     

Some probiotic properties of yeast isolates from infant faeces and Feta cheese

The use of modified atmospheres to prevent fungal growth and mycotoxin production in cheese was evaluated. Eight fungal species: Mucor plumbeus, Fusarium oxysporum, Byssochlamys fulva, B. nivea, Penicillium commune, P. roqueforti, Aspergillus flatus and Eurotium chevalieri were inoculated onto cheese and incubated under conditions of decreasing concentrations of O2 (5% to < 0.5%) and increasing concentrations of CO2 (20-40%). Fungal growth was measured by colony diameter and ergosterol content. All fungi examined grew in atmospheres containing 20% and 40% CO2 with 1% or 5% O2, but growth was reduced by 20-80%, depending on species, compared with growth in air. The formation of aflatoxins B1 and B2, roquerfortine C and cyclopiazonic acid was greatly decreased but not totally inhibited in these atmospheres. At 20% or 40% CO2 with < 0.5% O2, only B. nivea exhibited growth, which was very slow. Growth of F. oxysporum, B. fulca, P. commune and A. flavus showed good correlations between colony diameter and ergosterol content. However, for the other species correlations were inconsistent.     

Improvements in Mechanical Properties of 319 Al Alloy Engine Blocks Through Cost-Effective Solution Heat Treatment

The use of Al engine blocks has increased significantly to improve vehicle fuel efficiency. However, the gray cast iron cylinder liners cause the development of large tensile residual stress along the cylinder bores which necessitates the optimization of mechanical properties in this region to prevent premature engine failure. This study compared the microstructure of T4-treated Al billet castings of varying cooling rate to that of the cylinder region of T4-treated (current production schedule) Al engine blocks. The aim of this study was to develop a cost-effective small scale heat treatment optimization method for engine block production. Comparisons in microstructure between the engine block and the billet castings were carried out using optical and scanning electron microscopy. The results suggest that the microstructure and hardness at the top, middle, and bottom of the cylinder were similar to those of each representative billet casting, indicating that heat treatment resulted in successful replication of the engine block locations. In addition, tensile testing revealed that the YS and UTS increased slightly following T4 treatment for all billet castings, which was also observed at the middle of the engine block cylinder bridge. As such, this method can be an effective forerunner for future heat treatment optimization in Al engine block production.     

Josephson Coupling in Junctions Made of Monolayer Graphene Grown on SiC

Chemical vapor deposition has proved to be successful in producing graphene samples on silicon carbide (SiC) homogeneous at the centimeter scale in terms of Hall conductance quantization. Here, we report on the realization of co-planar diffusive Al/ monolayer graphene/ Al junctions on the same graphene sheet, with separations between the electrodes down to 200 nm. Robust Josephson coupling has been measured for separations not larger than 300 nm. Transport properties are reproducible on different junctions and indicate that graphene on SiC substrates is a concrete candidate to provide scalability of hybrid Josephson graphene/superconductor devices.     

Numerical solution of a stability problem in hydrodynamics

Details are given of techniques used for a numerical integration of the Navier-Stokes equations of hydrodynamics in the neighbourhood of a well-known steady solution (the Couette solution in cylindrical coordinates). A rule of numerical stability for the process of successive approximation is proposed; some preliminary results are described. Questo lavoro contiene i primi risultati di una ricerca sulla integrazione numerica di equazioni differenziali alle derivate parziali, iniziata recentemente presso il C. S. C. E. di Pisa. I primi due autori si sono divisi il compito di impostare il problema e di discutere le questioni di stabilità numerica di cui alla Sezione 5; mentre secondo e terzo autore hanno proposto il metodo di soluzione ed hanno condotto gli esperimenti numerici.     

Flux monitor diode radiation hardness testing

A flux monitor diode is being explored as an option for measurement of the output of an X-ray tube that is used for active transmission measurements on a pipe containing UF₆ gas. The measured flux can be used to correct for any instabilities in the X-ray tube or the high voltage power supply. For this measurement, we are using a silicon junction p-n photodiode, model AXUV100GX, developed by International Radiation Detectors, Inc. (IRD, Inc.). This diode has a silicon thickness of 104 μ and a thin (3-7 nm) silicon dioxide junction passivating, protective entrance window. These diodes have been extensively tested for radiation hardness in the UV range. However, we intend to operate mainly in the 10-40 keV X-ray region. We are performing radiation hardness testing over this energy range, with the energy spectrum that would pass through the diode during normal operation. A long-term measurement was performed at a high flux, which simulated over 80 years of operation. No significant degradation was seen over this time. Fluctuations were found to be within the 0.1% operationally acceptable error range. After irradiation, an I-V characterization showed a temporary irradiation effect which decayed over time. This effect is small because we operate the diode without external bias.     

Allocation and scheduling of Conditional Task Graphs

We propose an original, complete and efficient approach to the allocation and scheduling of Conditional Task Graphs (CTGs). In CTGs, nodes represent activities, some of them are branches and are labeled with a condition, arcs rooted in branch nodes are labeled with condition outcomes and a corresponding probability. A task is executed at run time if the condition outcomes that label the arcs in the path to the task hold at schedule execution time; this can be captured off-line by adopting a stochastic model. Tasks need for their execution either unary or cumulative resources and some tasks can be executed on alternative resources. The solution to the problem is a single assignment of a resource and of a start time to each task so that the allocation and schedule is feasible in each scenario and the expected value of a given objective function is optimized. For this problem we need to extend traditional constraint-based scheduling techniques in two directions: (i) compute the probability of sets of scenarios in polynomial time, in order to get the expected value of the objective function; (ii) define conditional constraints that ensure feasibility in all scenarios. We show the application of this framework on problems with objective functions depending either on the allocation of resources to tasks or on the scheduling part. Also, we present the conditional extension to the timetable global constraint. Experimental results show the effectiveness of the approach on a set of benchmarks taken from the field of embedded system design. Comparing our solver with a scenario based solver proposed in the literature, we show the advantages of our approach both in terms of execution time and solution quality.