Giacomo M. Bisio

Thermodynamics applied to oxygen enrichment of combustion air

Abstract In order to reduce overall fuel consumption, or to partially substitute a “valuable” fuel with a poor one, in industrial heating, oxygen enrichment of combustion air can be very effective. For the second option, a general criterion is stated in this paper for examining the suitability of oxygen enrichment in single cases. The topic is particularly interesting, as for the first time, it is now feasible to produce oxygen enriched air using permeable membranes on a commercial scale and with costs that are remarkably lower than those of other existing techniques. In this paper, the subject is investigated after some remarks about the definition of the “usable exergy” parameter, which was already proposed in previous papers by one of the authors and is here utilized for the above criterion.

On the recovery of LNG physical exergy by means of a simple cycle or a complex system

Abstract The maximum and minimum temperatures available limit the usable fraction (or Carnot efficiency) of a power cycle. The construction of LNG terminals and the need to vaporize LNG offers a thermal sink at a very much lower temperature than seawater. By using this thermal sink in a combined plant, it is possible to recover power from the vaporization of LNG. To this purpose, in this paper combined systems using LNG vaporization as low-temperature thermal sink are considered and their pros and cons are presented. A system utilizing waste energy as heat source and with a single working fluid is analyzed in detail. However, the use of a single fluid is not the best solution from a thermodynamic point of view. Thus, a series of cascading cycles is also outlined. In these systems, both the thermal source and the thermal sink are exploited as exergy sources.

Heat transfer, energy saving and pollution control in UHP electric-arc furnaces

The use of hot-water and evaporative cooling enables the residual energy potential of iron and steel works to be utilized. In particular, water-traversed wall elements are used at present in the top zone of an electric-arc furnace. Indeed, the remarkable increase in the electrical power has made the cooling of the wall of the furnace compulsory. Thus, it seems suitable to use the energy recovered in the cooling elements, instead of transferring it to the atmosphere via closed cooling towers. Nucleate boiling leads to a substantially more intensive cooling, but even a limited increase in the input heat flow can be dangerous. If the slag accretions, temperature and thermal power are examined in cases of steady state furnace operation and completely slag-covered arcs, it is found that the thermal losses decrease remarkably as the melting temperature of the slag adhering to the furnace shell increases. The aim of this paper is, first of all, an analysis of heat transfer phenomena in UHP (ultra high power) electric-arc furnaces. Then, energy and exergy analyses are dealt with after some remarks about exergy efficiency and chemical exergy of elements. In addition, means to reduce noise, air and water pollution are examined.

Analog VLSI circuits as physical structures for perception in early visual tasks

A variety of computational tasks in early vision can be formulated through lattice networks. The cooperative action of these networks depends on the topology of interconnections, both feedforward and recurrent ones. This paper shows that it is possible to consider a distinct general architectural solution for all recurrent computations of any given order. The Gabor-like impulse response of a second-order network is analyzed in detail, pointing out how a near-optimal filtering behavior in space and frequency domains can be achieved through excitatory/inhibitory interactions without impairing the stability of the system. These architectures can be mapped, very efficiently at transistor level, on very large scale integration (VLSI) structures operating as analog perceptual engines. The problem of hardware implementation of early vision tasks can, indeed, be tackled by combining these perceptual agents through suitable weighted sums. A 17-node analog current-mode VLSI circuit has been implemented on a CMOS 2 microm, NWELL, single-poly, and double-metal technology, to demonstrate the feasibility of the approach. Applications of the perceptual engine to various machine vision algorithms are proposed.

An experimental analog VLSI neural network with on-chip back-propagation learning

Analog VLSI implementations of artificial neural networks are usually considered efficient for the small area and the low power consumption they require, but very poor in terms of programmability. In this paper, we present an approach to the design of analog VLSI neural information-processing systems with on-chip learning capabilities. We describe a set of analog circuits for implementing the neural computational primitives of a Multi-Layer Perceptron, including the ones supporting a gradient-based learning algorithm (Back Propagation). Only supervision tasks are managed off chip.An experimental chip has been designed and fabricated using a standard digital 1.5 μm CMOS N-well technology. The chip contains 4 neurons and 32 synapses organized into a single-layer architecture with 8 inputs and 4 outputs. Measures illustrating the chip behavior during learning are reported.

Energy saving and some environment improvements in coke-oven plants

The enthalpy of inlet coal and fuel gas is discharged from a coke-oven plant in the following forms: chemical and thermal enthalpy of incandescent coke, chemical and thermal enthalpy of coke-oven gas, thermal enthalpy of combustion exhaust gas, and waste heat from the body of the coke oven. In recent years the recovery of several kinds of waste energy from coke ovens has been promoted mainly for energy saving purposes, but also for the improvement of environmental conditions. Among the various devices yet realized, the substitution of the conventional wet quenching method with a coke dry cooling is the most technically and economically convenient. The aim of this paper is mainly a review of the main types of coke dry cooling plants and a detailed examination of the influence of some parameters, particularly of temperature and pressure of the produced steam, and on the exergy efficiency of these plants.

On a general statement for efficiency

Abstract In this paper the conditions to define the efficiency of a process as applicable within the first and the second laws of thermodynamics are investigated. The aim of the note is in the first place of finding out a generalized statement of the efficiency, yielding values ranging in principle between one (for no irreversibilities) and zero (for no useful effect), whereas a relative entropy production varies between zero and one. Various kinds of processes are then examined to show the validity and the limits of the above statement In dieser Arbeit wird versucht die Bedingungen festzustellen, die eine Definition des Wirkungsgrades eines Prozesses erlauben, unter Beriicksicktigung des 1. und des 2. Haupsatzes der Thermodynamik. Das Ziel der Arbeit ist es, zuerst eine solche Definition des Wirkungsgrades zu erhalten, sodass der Wirkungsgrad grundsatzlich zwischcn 1 (bei umkehrbarem Prozess) und 0 (bei keiner Nutzwirkung) liegt, wahrend eine entsprechende relative Entropieerzeugung zwischen 0 und 1 schw...

Physical limits of integration and information processing in molecular systems

A review of the evolution of electronic information processing from small-scale integration to ultra-large-scale integration and beyond is presented recalling the milestones achieved in the development of electronic hardware. Physical principles which limit the size and performances of electronic circuits and the rate of information processing are discussed. In order to explore the new courses offered by organic molecular materials towards atomic-scale integration, the elementary computational capabilities of molecules are discussed by casting the quantum dynamic equations in the framework of system theory. Bond dynamics in polymeric networks is considered, thus showing the possibility of obtaining molecular probabilistic circuits.

Magnetic systems depending on three or two variables; thermodynamic analysis and some existing and possible applications

Until quite recently, the theory of continuous media dealt mainly with diamagnetic and paramagnetic fluids. The researchers did not consider strongly magnetizable fluids, probably because such media had not yet been discovered in natural conditions and did not exist until recently as manufactured products. However, in the early 1960 s, magnetic fluids (MF) could be synthetically prepared, and then, technological interest in MF grew rapidly. Besides, magnetic refrigeration has been used for over 60 years as a technology to achieve temperatures below 1 K, employing the magnetocaloric effect of some solid materials. However, in the last 20 years, the technology has been developing for refrigeration applications above 1 K up to and including heat pumps above room temperature. The work has been multinational in scope and has focussed on the analysis of magnetic thermodynamic systems, investigation of magnetic materials suitable for refrigerants and development of prototype refrigerators. After a synthetic review of the basic properties of MF, of magnetic refrigerators and heat pumps and of magnetic properties of living matter, the aim of this paper is a thermodynamic examination of these systems in comparison with the relations usually applied to fluids. Three independent variables are generally considered, whereas usually only two variables have been considered until now for what is known to the authors. Also, in the case of only two independent variables, some results are obtained which are original. Furthermore, some applications of MF are taken into account, in particular, possibilities of converting thermal into mechanical energy are examined.

Effects of weight discretization on the back propagation learning method: algorithm design and hardware realization

An architectural configuration for the back-propagation (BP) algorithm is illustrated. The circuit solution for the basic blocks is presented, and the effect of weight discretization on the BP algorithm is analyzed. It is demonstrated, through simulations, how the BP algorithm can be operated successfully with discretized weights. In particular, better performances can be achieved with an exponential discretization, i.e. the strength of weights varies exponentially with the controlling variable (voltage). The discretized voltage values differ by a quantity high enough that the neural network can be backed up with a refresh technique in combination with a multilevel dynamic memory that entails a particularly low wiring cost. A quasi-analog adaptive architecture is devised, properly matching the BP algorithm, and its CMOS circuit implementation is detailed. The mechanism controlling weight changes is simple enough to be reproduced locally at each synapsis site, thus meeting one of the requirements for an efficient storage technology for analog VLSI