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Material Cost (material + cost)

Distribution by Scientific Domains
Engineering40%
Polymers and Materials Science20%

Selected Abstracts

Thermoeconomic optimization for a finned-tube evaporator configuration of a roof-top bus air-conditioning system

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 4 2008
M. Khamis Mansour
Abstract This paper presents a methodology of a design optimization technique that can be useful in assessing the best configuration of a finned-tube evaporator, using a thermoeconomic approach. The assessment has been carried out on a direct expansion finned-tube evaporator of a vapor compression cycle for a roof-top bus air-conditioning (AC) system at a specified cooling capacity. The methodology has been conducted by studying the effect of some operational and geometrical design parameters for the evaporator on the entire cycle exergy destruction or irreversibility, AC system coefficient of performance (COP), and total annual cost. The heat exchangers for the bus AC system are featured by a very compact frontal area due to the stringent space limitations and structure standard for the system installation. Therefore, the current study also takes in its account the effect of the variation of the design parameters on the evaporator frontal area. The irreversibility due to heat transfer across the stream-to-stream temperature difference and due to frictional pressure drops is calculated as a function of the design parameters. A cost function is introduced, defined as the sum of two contributions, the investment expense of the evaporator material and the system compressor, and the operational expense of AC system that is usually driven by an auxiliary engine or coupled with the main bus engine. The optimal trade-off between investment and operating cost is, therefore, investigated. A numerical example is discussed, in which a comparison between the commercial evaporator design and optimal design configuration has been presented in terms of the system COP and evaporator material cost. The results show that a significant improvement can be obtained for the optimal evaporator design compared with that of the commercial finned-tube evaporator that is designed based on the conventional values of the design parameters. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Effects of chitosan solution concentration and incorporation of chitin and glycerol on dense chitosan membrane properties

JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2007
Paula Rulf Marreco Dallan
Abstract The aim of this work was to perform a systematic study about the effects induced by chitosan solution concentration and by chitin or glycerol incorporation on dense chitosan membranes with potential use as burn dressings. The membrane properties analyzed were total raw material cost, thickness, morphology, swelling ratio, tensile strength, percentage of strain at break, crystallinity, in vitro enzymatic degradation with lysozyme, and in vitro Vero cells adhesion. While the use of the most concentrated chitosan solution (2.5% w/w) increased membrane cost, it also improved the biomaterial mechanical resistance and ductility, as well as reduced membrane degradation when exposed for 2 months to lysozyme. The remaining evaluated properties were not affected by initial chitosan solution concentration. Chitin incorporation, on the other hand, reduced the membranes cost, swelling ratio, mechanical properties, and crystallinity, resulting in thicker biomaterials with irregular surface more easily degradable when exposed to lysozyme. Glycerol incorporation also reduced the membranes cost and crystallinity and increased membranes degradability after exposure to lysozyme. Strong Vero cells adhesion was not observed in any of the tested membrane formulations. The overall results indicate that the majority of the prepared membranes meet the performance requirements of temporary nonbiodegradable burn dressings (e.g. adequate values of mechanical resistance and ductility, low values of in vitro cellular adhesion on their surfaces, low extent of degradation when exposed to lysozyme solution, and high stability in aqueous solutions). © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2007 [source]

ROLE OF SATURATED FATTY ACIDS IN LIPASE PRODUCTION , USING PSEUDOMONAS AERUGINOSA

JOURNAL OF FOOD BIOCHEMISTRY, Issue 6 2007
A.N. SARAVANAN
ABSTRACT Complex substrates always induce substantial amount of enzyme production during hydrolysis by microorganisms. In this study, ghee was taken for its saturated fatty acid content and analyzed as an inducer for the production of lipase. With ghee emulsion, the bacterium Pseudomonas aeruginosa at optimal condition produced 60 units/min/L at 72 h. With olive oil emulsion, this organism produced only 41 units/min/L as maximum at 96 h. The saturated fatty acids present in ghee make it a hard substance for hydrolysis, which is the reason for the increased enzyme production. This was evaluated by the iodine number experiment. Ghee can also reduce the production cost whereas the costlier olive oil constitutes 25,50% of the total production cost for a commercial scale. The experimental results showed that the saturated fatty acids play an important role in lipase enzyme induction by P. aeruginosa. The use of ghee is cost-effective; hence, it can be used as a potential inducer for lipase production. PRACTICAL APPLICATIONS Lipases are industrially very important enzymes. They are used in pharmaceutical, food, soap and other industries. In lipase production, olive oil is the main constituent. Comparatively, olive oil is costlier; hence, it increases the production cost of lipase. So, this study was done to replace olive oil with a much cheaper ghee using Pseudomonas aeruginosa. The ghee-containing medium gave a very good result because of the presence of complex saturated fatty acids. The ghee-containing medium produced 60 units/min/L at 72 h. The olive oil medium, which contains mainly unsaturated fatty acids, produced only 41 units/min/L as maximum at 96 h. Hence, in the commercial scale, ghee can reduce raw material cost as well as operation time cost significantly when it is used as substrate. [source]

Design optimization for higher stabilized efficiency and reduced light-induced degradation in boron-doped Czochralski silicon solar cells

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 3 2002
B. Damiani
Traditional boron-doped Czochralski-grown Si solar cells are known to suffer from light-induced degradation (LID). By replacing B with Ga as the dopant in the Cz melt or by reducing the oxygen content by implementing the magnetic-Cz (MCz) growth technique, not only can LID be eliminated, but also higher efficiency manufacturable screen-printed cells can be achieved. The use of thinner wafers for cell fabrication can significantly reduce the impact of LID on conventional boron-doped Cz cells. Knowledge of the degraded cell parameters can be used to determine the optimal thickness for the highest stabilized efficiency. A methodology is developed to maximize the stabilized efficiency after LID by using thinner wafers. A combination of device modeling and experimental data is used to demonstrate that, for traditional B-doped Cz Si, which degraded from 75 to 20,,s, the optimum cell thickness is in the range of 150,190,,m for a back-surface recombination velocity of ,104 cm/s. This cell design reduces the material cost and the absolute efficiency degradation from 0.75% (375,,m device) to 0.24% (157,,m device) and gives the highest stabilized Cz cell efficiency. Copyright © 2002 John Wiley & Sons, Ltd. [source]

The Sequential Prisoner's Dilemma: Evidence on Reciprocation

THE ECONOMIC JOURNAL, Issue 468 2001
Kenneth Clark
We investigate how fairness concerns influence individual behaviour in social dilemmas. Using a Sequential Prisoner's Dilemma experiment we analyse the extent to which co-operation is conditional on first-mover co-operation, repetition, economic incentives, subject pool (United Kingdom vs. United States) and gender. We find the most important variable influencing co-operation is the first-mover's choice, supporting the argument that co-operative behaviour in social dilemmas reflects reciprocation rather than unconditional altruism. However, we also find that co-operation decreases with repetition, and reciprocation falls as its material cost rises. [source]

Architecture, Contingency and Crisis: An Interview with Slavoj ,i,ek

ARCHITECTURAL DESIGN, Issue 5 2010
Adrian Lahoud
Abstract The current and popular image of natural disaster disseminated by mass media is one of one-off catastrophe, the implied view being that these disasters have been exasperated if not instigated by climate change, which needs checking and balancing with sustainable measures. In his interview with Adrian Lahoud, the influential Slovenian philosopher Slavoj ,i,ek challenges this predominant view of nature as indomitable and temporarily imbalanced; and in so doing questions the fallacy that the ethical and material cost of consumerist lifestyles can be readdressed. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Optimal seismic design of steel frame buildings based on life cycle cost considerations

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 9 2003
Min Liu
Abstract A multi-objective optimization procedure is presented for designing steel moment resisting frame buildings within a performance-based seismic design framework. Life cycle costs are considered by treating the initial material costs and lifetime seismic damage costs as two separate objectives. Practical design/construction complexity, important but difficult to be included in initial cost analysis, is taken into due account by a proposed diversity index as another objective. Structural members are selected from a database of commercially available wide flange steel sections. Current seismic design criteria (AISC-LRFD seismic provisions and 1997 NEHRP provisions) are used to check the validity of any design alternative. Seismic performance, in terms of the maximum inter-storey drift ratio, of a code-verified design is evaluated using an equivalent single-degree-of-freedom system obtained through a static pushover analysis of the original multi-degree-of-freedom frame building. A simple genetic algorithm code is used to find a Pareto optimal design set. A numerical example of designing a five-storey perimeter steel frame building is provided using the proposed procedure. It is found that a wide range of valid design alternatives exists, from which a decision maker selects the one that balances different objectives in the most preferred way. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Microbial Fuel Cells in Relation to Conventional Anaerobic Digestion Technology

ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 3 2006
H. Pham
Abstract Conventional anaerobic digestion based bioconversion processes produce biogas and have as such been widely applied for the production of renewable energy so far. An innovative technology, based on the use of microbial fuel cells, is considered as a new pathway for bioconversion processes towards electricity. In comparison with conventional anaerobic digestion, the microbial fuel cell technology holds some specific advantages, such as its applicability for the treatment of low concentration substrates at temperatures below 20,°C, where anaerobic digestion generally fails to function. This provides some specific application niches of the microbial fuel cell technology where it does not compete with but complements the anaerobic digestion technology. However, microbial fuel cells still face important limitations in terms of large-scale application. The limitations involve the investment costs, upscale technical issues and the factors limiting the performance, both in terms of anodic and cathodic electron transfer. Research to render the microbial fuel cell technology more economically feasible and applicable should focus on reactor configuration, power density and the material costs. [source]

A Three-Dimensional Gold-Decorated Nanoporous Copper Core,Shell Composite for Electrocatalysis and Nonenzymatic Biosensing

ADVANCED FUNCTIONAL MATERIALS, Issue 14 2010
L.Y. Chen
Abstract Bimetallic core,shell nanostructures have attracted increasing attention due to their low material costs along with enhanced chemico-physical properties in comparison with their monometallic counterparts. Here, a novel gold-decorated nanoporous copper (Au@NPC) core,shell composite fabricated by a facile in situ hydrometallurgy approach is reported. Thin gold shells with a controllable thickness are homogeneously deposited onto the internal surfaces of 3D nanoporous copper via a spontaneous displacement reaction while nanoporous copper is utilized as a reduction agent as well as 3D template and substrate. The resulting inexpensive core,shell nanostructure exhibits significant electrocatalytic activity for the oxidation of methanol and high non-enzymatic sensitivity in detecting glucose. [source]

Structural Power and Public Policy: A Signaling Model of Business Lobbying in Democratic Capitalism

POLITICAL STUDIES, Issue 1 2005
Patrick Bernhagen
This paper develops a signaling model of corporate lobbying in democratic capitalist societies to analyze the conditions that lead to a powerful political position of business. Proceeding from the traditional dichotomy of structural economic determinants versus business' political action, our model predicts the conditions under which elected political decisionmakers modify their policy pledges to accommodate business' political preferences, or override business' lobbying messages and honor their pledges. Our results show that the structural power of business over public policy is contingent on two variables: the size of reputation costs of business in relation to its material costs of lobbying; and the ratio of the policymaker's reputation constraints from policy commitments and campaign pledges to the electoral costs arising from adverse effects of policy. We evaluate our model using case studies of business lobbying on environmental and financial services regulation in Britain and Germany. [source]