Home  About us  Contact
 

Specific Work (specific + work)

Distribution by Scientific Domains
Engineering60%
Humanities and Social Sciences40%

Selected Abstracts

Cost numerical optimization of the triple-pressure steam-reheat gas-reheat gas-recuperated combined power cycle that uses steam for cooling the first GT

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 15 2008
A. M. Bassily
Abstract Optimization is an important method for improving the efficiency and power of the combined cycle. In this paper, the triple-pressure steam-reheat gas-reheat gas-recuperated combined cycle that uses steam for cooling the first gas turbine (the regular steam-cooled cycle) was optimized relative to its operating parameters. The optimized cycle generates more power and consumes more fuel than the regular steam-cooled cycle. An objective function of the net additional revenue (the saving of the optimization process) was defined in terms of the revenue of the additional generated power and the costs of replacing the heat recovery steam generator (HRSG) and the costs of the additional operation and maintenance, installation, and fuel. Constraints were set on many operating parameters such as air compression ratio, the minimum temperature difference for pinch points (,Tppm), the dryness fraction at steam turbine outlet, and stack temperature. The net additional revenue and cycle efficiency were optimized at 11 different maximum values of turbine inlet temperature (TIT) using two different methods: the direct search and the variable metric. The optima were found at the boundaries of many constraints such as the maximum values of air compression ratio, turbine outlet temperature (TOT), and the minimum value of stack temperature. The performance of the optimized cycles was compared with that for the regular steam-cooled cycle. The results indicate that the optimized cycles are 1.7,1.8 percentage points higher in efficiency and 4.4,7.1% higher in total specific work than the regular steam-cooled cycle when all cycles are compared at the same values of TIT and ,Tppm. Optimizing the net additional revenue could result in an annual saving of 21 million U.S. dollars for a 439,MW power plant. Increasing the maximum TOT to 1000°C and replacing the stainless steel recuperator heat exchanger of the optimized cycle with a super-alloys-recuperated heat exchanger could result in an additional efficiency increase of 1.1 percentage point and a specific work increase of 4.8,7.1%. The optimized cycles were about 3.3 percentage points higher in efficiency than the most efficient commercially available H-system combined cycle when compared at the same value of TIT. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Analysis and cost optimization of the triple-pressure steam-reheat gas-reheat gas-recuperated combined power cycle

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 2 2008
A. M. Bassily
Abstract Increasing the inlet temperature of gas turbine (TIT) and optimization are important methods for improving the efficiency and power of the combined cycle. In this paper, the triple-pressure steam-reheat gas-reheat recuperated combined cycle (the Regular Gas-Reheat cycle) was optimized relative to its operating parameters, including the temperature differences for pinch points (,TPP). The optimized triple-pressure steam-reheat gas-reheat recuperated combined cycle (the Optimized cycle) had much lower ,TPP than that for the Regular Gas-Reheat cycle so that the area of heat transfer of the heat recovery steam generator (HRSG) of the Optimized cycle had to be increased to keep the same rate of heat transfer. For the same mass flow rate of air, the Optimized cycle generates more power and consumes more fuel than the Regular Gas-Reheat cycle. An objective function of the net additional revenue (the saving of the optimization process) was defined in terms of the revenue of the additional generated power and the costs of replacing the HRSG and the additional fuel. Constraints were set on many operating parameters such as the minimum temperature difference for pinch points (,TPPm), the steam turbines inlet temperatures and pressures, and the dryness fraction at steam turbine outlet. The net additional revenue was optimized at 11 different maximum values of TIT using two different methods: the direct search and variable metric. The performance of the Optimized cycle was compared with that for the Regular Gas-Reheat cycle and the triple-pressure steam-reheat gas-reheat recuperated reduced-irreversibility combined cycle (the Reduced-Irreversibility cycle). The results indicate that the Optimized cycle is 0.17,0.35 percentage point higher in efficiency and 5.3,6.8% higher in specific work than the Reduced-Irreversibility cycle, which is 2.84,2.91 percentage points higher in efficiency and 4.7% higher in specific work than the Regular Gas-Reheat cycle when all cycles are compared at the same values of TIT and ,TPPm. Optimizing the net additional revenue could result in an annual saving of 33.7 million US dollars for a 481 MW power plant. The Optimized cycle was 3.62 percentage points higher in efficiency than the most efficient commercially available H-system combined cycle when compared at the same value of TIT. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Numerical Simulation of the Application of NiTi Alloys in Medical Technologies

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2005
Daniel Christ
Shape memory alloys are nowadays already established as a material which is able to solve exceptional tasks in practical applications. Particularly, its utilization in the field of medical technologies increases steadily. For example micro tools (staple, catheters) and implants (coronary stents) are made out of Nickel-Titanium well known as a basic shape memory alloy. Apart from the advantages like the avoidance of auxiliary components and joints in the system and to utilize the high volume specific work of shape memory alloys, NiTi alloys exhibit a good biocompatibility. This property is necessary with regard to either permanent or temporary implants. To optimize the use of NiTi alloys in the scope of medical technologies, the support of the development of applicable tools by numerical simulations is highly recommended. However the complex material behaviour containing a profoundly thermomechanical coupling poses indeed a big challenge to the material modeling and its implementation into a finite element code. Particularly, the material model proposed by Helm [1] proves to be a firm model containing the most common properties of shape memory alloys, as the pseudoelasticity, the shape memory effect and the two-way effect. In the present contribution the FE modelling of a medical staple used in foot surgery is presented by considering the model of Helm which was investigated by the authors to improve its performance in the finite element method [2]. The foot staple, produced by a group of members of the SFB 459 which is funded by the DFG, avails the shape memory effect to excite the desired clamping effect [3]. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Dating the Gesta martyrum: a manuscript-based approach

EARLY MEDIEVAL EUROPE, Issue 3 2000
Clare Pilsworth
The gesta martyrum are an anonymous and disparate group of texts celebrating saints venerated in early medieval Rome as having been martyred in that city. This paper investigates the problems involved in placing these texts in their early medieval contexts. Since the beginning of the twentieth century, when scholarship moved away from attempts to identify a core of authentic ancient tradition in these early medieval narratives, most work on the corpus has concentrated on dating the composition of the accounts of individual martyrs. Given the sparsity of absolute chronological markers through references or citations in other written sources, this has inevitably rested on circumstantial evidence and the reconstruction of probable contexts for the redaction of specific works. This paper argues that much new light can be shed on the development of the cult of Roman martyrs if we shift the focus of our investigation from the origin and composition of the Urtexts to the surviving manuscript witnesses , all bar one eighth century or later , and the complex process of transmission which they document. The earliest copies of gesta martyrum, in both legendaries and other manuscripts, reveal surprisingly diverse contexts of transmission. Detailed investigation of Vienna National bibliothek 357, which Dufourcq argued contains a copy of a collection of martyr-narratives available to Gregory the Great, shows that in fact this manuscript sheds light on interest in Roman martyrs north of the Alps in the late Carolingian period, and the networks of contact and communication through which information about the Roman martyrs was transmitted across time and space. [source]

The Bishops' Ban of 1599 and the Ideology of English Satire

LITERATURE COMPASS (ELECTRONIC), Issue 5 2010
William R. Jones
On June 1, 1599, the Archbishop of Canterbury and the Bishop of London banned the further printing of satires, epigrams, and unlicensed histories and plays. Furthermore, the order demanded the immediate recall and burning of specific works, many of which were verse imitations of the Roman satirist Juvenal. Although the order itself lacks specific motivational language, current explanations tend to foreground the potentially obscene and/or libelous nature of the recalled works. Comparatively little attention has been paid, however, to the internal ideologies of the banned satires themselves and to the dialogue between the satires and the cultural and political conditions that inspired them. Instead of an ad hoc response to any one particular transgression, this essay argues for the Ban as an attempt to stem the growing cultural influence of a particularly unorthodox mode of Juvenalian imitative satire expressed most forcefully in John Marston's banned work, The Scourge of Villanie. Marston's rejection of all established belief systems, especially the conservative literary traditions of native English and Horatian imitative satire, in favor of a highly individualistic and indecorous mode of social representation, was simply too ideologically destabilizing for the bishops to tolerate. In support of this reading, two relatively underexplored pieces of evidence are examined: first, the reprieve granted to Joseph Hall's imitative satire entitled Virgidemiarum, which attempts to negotiate an ideologically safe middle-ground between the radical Juvenalian mode and the conservative Horatian tradition; and second, the contemporary reflections on the bishops' prohibition within John Weever's 1599 Epigrams, his 1600 pastoral Faunus and Melliflora, and his 1601 direct attack on Marston in The Whipping of the Satyre. Weever's support of the bishops' actions derives from his identification of the banned Juvenalian mode as not merely morally offensive or personally defamatory, but as a tangible threat to the ideological stability of the English nation. [source]