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Conflicting Requirements (conflicting + requirement)
Selected AbstractsEffect of Nickel Oxide/Yttria-Stabilized Zirconia Anode Precursor Sintering Temperature on the Properties of Solid Oxide Fuel CellsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2000Søren Primdahl An NiO/yttria-stabilized zirconia (YSZ) layer sintered at temperatures between 1100° and 1500°C onto dense YSZ electrolyte foils forms the precursor structure for a porous Ni/YSZ cermet anode for solid oxide fuel cells. Conflicting requirements for the electrochemical performance and mechanical strength of such cells are investigated. A minimum polarization resistance of 0.09 ,.cm2at 1000°C in moist hydrogen is obtained for sintering temperatures of 1300°,1400°C. The mechanical strength of the cells decreases with increased sintering temperature because of the formation of channel cracks in the electrode layers, originating in a thermal expansion coefficient mismatch between the layers. [source] Simultaneous Optimization of Luminance and Color Chromaticity of Phosphors Using a Nondominated Sorting Genetic AlgorithmADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Asish Kumar Sharma Abstract Acquiring materials that simultaneously meet two or more conflicting requirements is very difficult. For instance, a situation wherein the color chromaticity and photoluminescence (PL) intensity of phosphors conflict with one another is a frequent problem. Therefore, identification of a good phosphor that simultaneously exhibits both desirable PL intensity and color chromaticity is a challenge. A high-throughput synthesis and characterization strategy that was reinforced by a nondominated sorting genetic algorithm (NSGA)-based optimization process was employed to simultaneously optimize both the PL intensity and color chromaticity of a MgO,ZnO,SrO,CaO,BaO,Al2O3,Ga2O3,MnO system. NSGA operations, such as Pareto sorting and niche sharing, and the ensuing high-throughput synthesis and characterization resulted in identification of promising green phosphors, i.e., Mn2+ -doped AB2O4 (A,=,alkali earth, B,=,Al and Ga) spinel solid solutions, for use in either plasma display panels or cold cathode fluorescent lamps. [source] Complexity versus integrity solution in adaptive fuzzy-neural inference modelsINTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 5 2008Georgi M. Dimirovski This paper explores aspects of computational complexity versus rule reduction and of integrity preservation versus optimality index, which have become an issue of considerable concern in learning techniques for adaptive fuzzy inference models. In control-oriented applications of adaptive fuzzy inference systems, implemented as fuzzy-neural networks, a balanced observation of these conflicting requirements appeared rather important for a good yet feasible application design. The focus is confined to a family of adaptive fuzzy inference systems that can be interpreted as a partially connected multilayer feedforward neural networks employing Gaussian activation function. The knowledge base rules are designed implying the connections are a priori fixed, and then the respective strengths adapted on the grounds of input and output data sets. Information granulation plays a significant role too. These as well as membership-function parameters ought to be adapted in a learning-training process via the minimization of an appropriate error function. © 2008 Wiley Periodicals, Inc. [source] A stability guaranteed active fault-tolerant control system against actuator failuresINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 12 2004Midori Maki Abstract In this paper, a new strategy for fault-tolerant control system design has been proposed using multiple controllers. The design of such controllers is shown to be unique in the sense that the resulting control system neither suffers from the problem of conservativeness of conventional passive fault-tolerant control nor from the risk of instability associated with active fault-tolerant control in case that an incorrect fault detection and isolation decision is made. In other words, the stability of the closed-loop system is always ensured regardless of the decision made by the fault detection and isolation scheme. A correct decision will further lead to optimal performance of the closed-loop system. This paper deals with the conflicting requirements among stability, redundancy, and graceful degradation in performance for fault-tolerant control systems by using robust control techniques. A detailed design procedure has been presented with consideration of parameter uncertainties. Both total and partial actuator failures have been considered. This new control strategy has been demonstrated by controlling a McDonnell F-4C airplane in the lateral-direction through simulation. Copyright © 2004 John Wiley & Sons, Ltd. [source] Joint spectrum and power optimization in the design of the UMTS satellite componentINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 6 2001Ernestina Cianca Abstract The paper provides a power and spectrum joint analysis of the universal mobile telecommunications system (UMTS) satellite component, based on the wideband code division multiple access (W-CDMA) air interface. In fact, power and spectral efficiency may become highly conflicting requirements in a satellite system and a trade-off analysis is needed to drive a proper dimensioning of the satellite. The proposed approach allows a dimensioning of the satellite component either in terms of orbit and power budget or in terms of additional capacity for the terrestrial section, for specified orbit and power limitations. The impact of candidate frequency bands, orbit type and diversity on both spectral and power requirements of the satellite component is evaluated. For given traffic requirements, power-vs-spectrum trade-off is proposed which ensures a proper resources utilization. The efficiency evaluation accounts for: beams overlapping, ortho gonality, voice activity factor, diversity and cross-polarization frequency reuse. Perfect power control is assumed and the effect of the excess power required by the shadowed users is accounted for in the interference calculation. Furthermore, still in the frame of a proper resource exploitation, a possible optimization of capacity through the use of unpaired bands in the two link directions is analysed. Copyright © 2001 John Wiley & Sons, Ltd. [source] Developments in EU biofuels policy related to sustainability issues: overview and outlookBIOFUELS, BIOPRODUCTS AND BIOREFINING, Issue 4 2007Marc Londo Abstract In the current debate on present and future biofuels policy, sustainability issues play an important role. In this perspective, we discuss a number of factors in the framing of the biofuels sustainability debate, and describe their role over the last 25 years or so in which biofuels have been on the political agenda. Our first conclusion is that biofuels policy is related to several underlying objectives, such as climate change, security of supply and other drivers. Therefore, the policy will structurally need to be monitored in its impacts, in order to keep these impacts in concordance with these objectives. In the long term, biofuels policy might be substituted by instruments that more directly relate to the objectives. Second, current sustainability issues concerning biofuels relate to either the production chain or to the regional system in which biofuels compete for land. Finding suitable indicators and setting up monitoring schemes are key challenges. Furthermore, a safeguarding scheme needs to meet two conflicting requirements: on the one hand it is important to implement it over many regions and many sectors (including non-energy), but on the other hand the problem requires implementation in the short term. Starting with monitoring only may cause an issue of legitimacy. Finally, we propose some elements for a robust development strategy. This includes pushing forward with a sustainability safeguarding scheme, within the given constraints. During the start-up period of such schemes, non-certified biofuels and feedstock might be discouraged, simultaneously stimulating production initiatives operating under certification. © 2007 Society of Chemical Industry and John Wiley & Sons, Ltd [source] Perfusion seeding of channeled elastomeric scaffolds with myocytes and endothelial cells for cardiac tissue engineeringBIOTECHNOLOGY PROGRESS, Issue 2 2010Robert Maidhof Abstract The requirements for engineering clinically sized cardiac constructs include medium perfusion (to maintain cell viability throughout the construct volume) and the protection of cardiac myocytes from hydrodynamic shear. To reconcile these conflicting requirements, we proposed the use of porous elastomeric scaffolds with an array of channels providing conduits for medium perfusion, and sized to provide efficient transport of oxygen to the cells, by a combination of convective flow and molecular diffusion over short distances between the channels. In this study, we investigate the conditions for perfusion seeding of channeled constructs with myocytes and endothelial cells without the gel carrier we previously used to lock the cells within the scaffold pores. We first established the flow parameters for perfusion seeding of porous elastomer scaffolds using the C2C12 myoblast line, and determined that a linear perfusion velocity of 1.0 mm/s resulted in seeding efficiency of 87% ± 26% within 2 hours. When applied to seeding of channeled scaffolds with neonatal rat cardiac myocytes, these conditions also resulted in high efficiency (77.2% ± 23.7%) of cell seeding. Uniform spatial cell distributions were obtained when scaffolds were stacked on top of one another in perfusion cartridges, effectively closing off the channels during perfusion seeding. Perfusion seeding of single scaffolds resulted in preferential cell attachment at the channel surfaces, and was employed for seeding scaffolds with rat aortic endothelial cells. We thus propose that these techniques can be utilized to engineer thick and compact cardiac constructs with parallel channels lined with endothelial cells. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] | |||||||||||||