Die Bestimmung des Schalengehaltes im Kakao

Ohne Zusammenfassung     

Job Allocation Strategies with User Run Time Estimates for Online Scheduling in Hierarchical Grids

We address non-preemptive non-clairvoyant online scheduling of parallel jobs on a Grid. We consider a Grid scheduling model with two stages. At the first stage, jobs are allocated to a suitable Grid site, while at the second stage, local scheduling is independently applied to each site. We analyze allocation strategies depending on the type and amount of information they require. We conduct a comprehensive performance evaluation study using simulation and demonstrate that our strategies perform well with respect to several metrics that reflect both user- and system-centric goals. Unfortunately, user run time estimates and information on local schedules does not help to significantly improve the outcome of the allocation strategies. When examining the overall Grid performance based on real data, we determined that an appropriate distribution of job processor requirements over the Grid has a higher performance than an allocation of jobs based on user run time estimates and information on local schedules. In general, our experiments showed that rather simple schedulers with minimal information requirements can provide a good performance.     

Derogation and distancing as terror management strategies: The moderating role of need for closure and permeability of group boundaries.

Previous research has revealed that when individuals are confronted with criticism of a personally relevant group, mortality salience can lead to either derogation of the source of criticism or distancing from the group. In this article, the authors investigated closure as a potential moderator of these reactions. In Study 1, salience led to greater derogation of a critic of a relevant group among high-need-for-closure participants but led to distancing from the group among low need-for-closure participants. Study 2 showed that when a relevant group was criticized, mortality salience led to greater derogation among participants who were led to believe that the boundaries of that group were impermeable but led to greater distancing among participants who were made aware of the permeable nature of the group boundaries. These findings demonstrate that closure of group membership moderates reactions to criticism of a personally relevant group after mortality salience. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Biomass and central receiver system (CRS) hybridization: Volumetric air CRS and integration of a biomass waste direct burning boiler on steam cycle

Concentrated solar power (CSP) plants generate an almost continuous flow of fully dispatchable “renewable” electricity and can replace the present fossil fuel power plants for base load electricity generation. Nevertheless, actual CSP plants have moderate electricity costs, in most cases quite low capacity factors and transient problems due to high inertia. Hybridization can help solve these problems and, if done with the integration of forest waste biomass, the “renewable” goal can be maintained, with positive impact on forest fire reduction. Local conditions, resources and feed in tariffs have great impact on the economical and technical evaluation of hybrid solutions; one of the premium European locations for this type of power plants is the Portuguese Algarve region.Due to the concept innovation level, conservative approaches were considered to be the best solutions. In this perspective, for a lower capital investment 4 MWe power plant scale, the best technical/economical solution is the hybrid CRS/biomass power plant HVIB3S4s with CS3 control strategy. It results in a levelized electricity cost (LEC) of 0.146 €/kWh, with higher efficiency and capacity factor than a conventional 4 MWe CRS. A larger 10 MWe hybrid power plant HVIB3S10s could generate electricity with positive economical indicators (LEC of 0.108 €/kWh and IRR of 11.0%), with twice the annual efficiency (feedstock to electricity) and lower costs than a conventional 4 MWe CRS. It would also lead to a 17% reduction in biomass consumption (approximately 12,000 tons less per year) when compared with a typical 10 MWe biomass power plant – FRB10; this would be significant in the case of continuous biomass price increase.     

Numerical analysis of the tubular heat exchanger designed for co-generating units on the basis of microturbines

The application of numerical simulations using the computational fluid dynamics (CFD) analysis when mapping processes in the course of which the heat transmission occurs has become an essential part of the heat transfer systems. The present contribution deals with the possibility to use the waste heat of the flue gas produced by small microturbines. The waste heat is mapped by means of both the numerical simulations applying the FLUENT software and the practical experiment. Utilizing a part of the waste heat for water heating and decreasing the outlet temperature of the flue gas into atmosphere when applying in co-generating units represents one of the partial benefits. The present paper brings information concerning the newly designed type of heat exchanger including the results of its numerical analysis.The analysed heat exchanger designed in the system with microturbine (MT) C30 reached generally the efficiency of 75%. Both the results of simulations and the carried out practical experiment confirmed the temperature of the flue gas to be sufficient behind the exchanger to prevent the condensation of water from the flue gas. On the contrary, except for heating water the exchanger under consideration offers – thanks to its design – also other possibilities to use of the flue gas. The practical experiment confirmed the results of the CFD prediction with rather small differences as the temperature of water obtained from the exchanger was 359 K and the designed shape of the exchanger did not result in substantial pressure losses in flue gas approximately 50 Pa. The mean logarithmic temperature difference of the mapped and verified exchanger was ～203 K.     

Is cumulative fossil energy demand a useful indicator for the environmental performance of products?

The appropriateness of the fossil Cumulative Energy Demand (CED) as an indicator for the environmental performance of products and processes is explored with a regression analysis between the environmental life-cycle impacts and fossil CEDs of 1218 products, divided into the product categories "energy production", "material production", "transport", and "waste treatment". Our results show that, for all product groups but waste treatment, the fossil CED correlates well with most impact categories, such as global warming, resource depletion, acidification, eutrophication, tropospheric ozone formation, ozone depletion, and human toxicity (explained variance between 46% and 100%). We conclude that the use of fossil fuels is an important driver of several environmental impacts and thereby indicative for many environmental problems. It maytherefore serve as a screening indicatorfor environmental performance. However, the usefulness of fossil CED as a stand-alone indicator for environmental impact is limited by the large uncertainty in the product-specific fossil CED-based impact scores (larger than a factor of 10 for the majority of the impact categories; 95% confidence interval). A major reason for this high uncertainty is nonfossil energy related emissions and land use, such as landfill leachates, radionuclide emissions, and land use in agriculture and forestry.     

Exergetic analysis of a desiccant cooling system: searching for performance improvement opportunities

The current increase of the energy consumption of buildings requires new approaches to solve economic, environmental and regulatory issues. Exergy methods are thermodynamic tools searching for sources of inefficiencies in energy conversion systems that the current energy techniques may not identify. Desiccant cooling systems (DCS) are equipments applied to dehumidifying and cooling air streams, which may provide reductions of primary energy demand relatively to conventional air‐conditioning units. In this study, a detailed thermodynamic analysis of open‐cycle DCS is presented. It aims to assess the overall energy and exergy performance of the plant and identify its most inefficient sub‐components, associated to higher sources of irreversibilities. The main limitations of the energy methods are highlighted, and the opportunities given by exergy approach for improving the system performance are properly identified. As case study, using a pre‐calibrated TRNSYS model, the overall energy and exergy efficiency of the plant were found as 32.2% and 11.8%, respectively, for a summer week in Mediterranean climate. The exergy efficiency defect identified the boiler (69.0%) and the chiller (12.3%) as the most inefficient components of the plant, so their replacement by high efficient systems is the most rational approach for improving its performance. As alternative heating system to the boiler, a set of different technologies and integration of renewables were proposed and evaluated applying the indicators: primary energy ratio (PER) and exergy efficiency. The heating system fuelled by wood was found as having the best primary energy performance (PER = 109.6%), although the related exergy efficiency is only 11.4%. The highest exergy performance option corresponds to heat pump technology with coefficient of performance (COP) = 4, having a PER of 50.6% and exergy efficiency of 28.2%. Additionally, the parametric analyses conducted for different operating conditions indicate that the overall irreversibility rate increases moderately for larger cooling effects and more significant for higher dehumidification rates. Copyright © 2013 John Wiley & Sons, Ltd.     

Sustainability in bridge construction processes

Sustainability must be seen as a global issue. In order to achieve that goal, it is necessary to apply its principles to all industrial activities, including those that are not traditionally engaged with such guidelines, which is the case of Bridge Construction. This paper evaluates the consumption of steel and energy and the emissions of carbon dioxide due to the use of movable scaffolding systems (MSS) in the Bridge Construction industry. The values obtained considering the use of conventional MSS are compared with the ones obtained using a new sustainable technology which is herein synthetically described—the organic prestressing system (OPS). In order to compare the sustainability of the two systems, a prediction of the material and energy consumptions, and CO₂ emissions for traditional MSS and for MSS equipped with OPS is performed until 2025.