Global and local emission impact assessment of distributed cogeneration systems with partial-load models

Small-scale distributed cogeneration technologies represent a key resource to increase generation efficiency and reduce greenhouse gas emissions with respect to conventional separate production means. However, the diffusion of distributed cogeneration within urban areas, where air quality standards are quite stringent, brings about environmental concerns on a local level. In addition, partial-load emission worsening is often overlooked, which could lead to biased evaluations of the energy system environmental performance.     

A static mapping heuristics to map parallel applications to heterogeneous computing systems

In order to minimize the execution time of a parallel application running on a heterogeneously distributed computing system, an appropriate mapping scheme is needed to allocate the application tasks to the processors. The general problem of mapping tasks to machines is a well‐known NP‐hard problem and several heuristics have been proposed to approximate its optimal solution. In this paper we propose a static graph‐based mapping algorithm, called Heterogeneous Multi‐phase Mapping (HMM), which permits suboptimal mapping of a parallel application onto a heterogeneous computing distributed system by using a local search technique together with a tabu search meta‐heuristic. HMM allocates parallel tasks by exploiting the information embedded in the parallelism forms used to implement an application, and considering an affinity parameter, that identifies which machine in the heterogeneous computing system is most suitable to execute a task. We compare HMM with some leading techniques and with an exhaustive mapping algorithm. We also give an example of mapping of two real applications using HMM. Experimental results show that HMM performs well demonstrating the applicability of our approach. Copyright © 2005 John Wiley & Sons, Ltd.     

A game theoretic coordination for trading capacity in multisite factory environment

Multisite factories geographically distributed often have to implement an opportune tool to integrate their resources and demand forecasts in order to gather a specific production objective. The proposed research develops a distributed approach, for a network of independent enterprises, able to facilitate the capacity process by using a multiagent architecture and a cooperative protocol. The last one is based on game theory and, in particular, on Nash bargaining solution. Moreover, a discrete simulation environment has been developed to compare the proposed approach with the one in which no cooperation among enterprises exist. Several simulation scenarios were conducted to analyze the performances’ trends in various environment conditions. The goal has been the evaluation of the unallocated capacity, the unsatisfied demand, the profits generated by the network, the distribution of the transactions among the plants, and the number of activated links among plants. The simulation results show that the proposed approach leads to a better performance indexes and more relevant benefits when the dynamicity of the environment growths.     

Cogeneration planning under uncertainty. Part II: Decision theory-based assessment of planning alternatives

This paper discusses specific models and analyses to select the best cogeneration planning solution in the presence of uncertainties on a long-term time scale, completing the approach formulated in the companion paper (Part I). The most convenient solutions are identified among a pre-defined set of planning alternatives according to decision theory-based criteria, upon definition of weighted scenarios and by using the exceeding probabilities of suitable economic indicators as decision variables. Application of the criteria to a real energy system with various technological alternatives operated under different control strategies is illustrated and discussed. The results obtained show that using the Net Present Cost indicator it is always possible to apply the decision theory concepts to select the best planning alternative. Other economic indicators like Discounted Payback Period and Internal Rate of Return exhibit possible application limits for cogeneration planning within the decision theory framework.     

A study of the interaction between fluorescein sodium salt and bovine serum albumin by steady-state fluorescence

The binding of fluorescein sodium salt with three kinds of commercially available bovine serum albumin (BSA) of different grades of purity was investigated at 288, 298 and 313 K by fluorescence and absorption measurements at pH 7.50. The association and dissociation constants K_a and K_d were determined by the quenching of BSA fluorescence in the presence of fluorescein sodium salt. The best results were obtained by fitting raw data by non-linear regression and Lineweaver–Burk equations. The modified Stern–Volmer and Scatchard plots gave less reliable data since the fitting was much more difficult.The agreement of the constants for the three sets of measurements coming from the different BSA was not as good as expected. BSA binding properties differ depending on the different BSA grades of purity. Actually, the binding constants found for the three BSAs used differed in the same set of interactions, even by keeping the experimental conditions constant. These results are a novelty in the field of BSA–ligand binding studies and should be taken into account for future binding studies using BSA. Actually, a large number of aspects should be considered including the grade of purity and the presence of BSA covalent and non-covalent dimers, trimers and oligomers in solution which can affect the goodness of the binding results.     

Creating portable and efficient packet processing applications

Network processors are special-purpose programmable units deployed in many modern high-speed network devices, which combine flexibility and high performance. However, software development for these platforms is traditionally cumbersome due both to the lack of adequate programming abstractions and to the impossibility of reusing the same software on different hardware platforms.     

Donkey’s milk protein fractions characterization

Donkey’s milk may be considered a valid alternative, for infant nutrition, to powdered milks, soybean milk or other formulas, since its composition in lipids and proteins is very close to human milk. The aim of the present study is to characterize “donkey’s milk” product, especially with regard to the protein fractions. Three different chromatographic approaches for donkey’s milk proteins separation are described, based on their different isoelectric points, hydrophobicity and molecular mass. The proteins obtained were further separated by sodium dodecyl sulphate polyacrylamide gel electrophoresis and identified by N-terminal sequencing. α_S1- and β-caseins, lysozyme, α-lactalbumin, β-lactoglobulin were identified. Furthermore, the content of α-lactalbumin, β-lactoglobulin, and lysozyme in donkey’s milk was determined by a reversed-phase HPLC method. The β-lactoglobulin and α-lactalbumin content was 3.75 and 1.8 mg/ml, respectively (mean values). The present study showed the nutritional properties of donkey’s milk characterized by low casein and high lysozyme content (1.0 mg/ml) compared with other kinds of milks.     

Capacity sharing in a network of enterprises using the Gale–Shapley model

In this paper, we analyze a model of capacity sharing for a set of independent firms, geographically distributed, that often have to implement an opportune tool to integrate their resources and demand forecasts in order to gather a specific production objective. We formulate the problem as a cooperative game and identify a capacity sharing solution using the Gale–Shapley model. The allocation rule takes into account the utility functions of the involved firms, and we show how the capacity allocation rule can be designed to induce all firms to report truthfully their information. Moreover, we show that, under this allocation rule, truth telling is a dominant strategy, with each firm reporting truthfully its private information, regardless of the reporting decisions of other firms. Moreover, the proposed research develops a distributed approach able to facilitate the capacity sharing process by using a multi-agent architecture; then a discrete simulation environment has been developed to compare the proposed approach with a centralized one. Several simulation scenarios were conducted to analyze the performances' trends in various environment conditions.     

A comparative assessment on hydrogen production from low- and high-temperature electrolysis

In this work a comparative analysis between low- and high-temperature electrolysis for hydrogen generation is assessed. A hydrogen production system based on Solid Oxide Electrolysis Cells (SOEC) is designed and modeled and compared to the performance of a more mature system based on PEM technology. The SOEC system mainly consists of an SOEC stack, a heat recovery system and a hydrogen compression section. Experimental data measured in steam electrolysis tests performed on single solid oxide cells were utilized into the model to characterize the stack performance. The model carries out a thermodynamic analysis in order to calculate the energy efficiency and the exergetic consumption of the system; these performances are subsequently compared with those of a low-temperature hydrogen generation system evaluated from experimental data measured in test sessions performed on a complete BoP integrating a pressurized Proton Exchange Membrane (PEM) electrolyser. The comparison is carried out with the two electrolysis systems generating hydrogen at the same production rate and pressure. The results of this study show that the modeled SOEC hydrogen generation system can compete with the PEM electrolyser, achieving better performance than the low-temperature system at hydrogen production rate higher than 18.3 g h⁻¹ (corresponding to 0.25 A cm⁻²) and showing an energy efficiency up to 14% higher than the PEM system at 1 A cm⁻².