Price formation in electricity forward markets and the relevance of systematic forecast errors

Since the liberalisation of the European electricity sector, forward and futures contracts have gained significant interest of market participants due to risk management reasons. For pricing of these contracts an important fact concerns the non-storability of electricity. In this case, according to economic theory, forward prices are related to the expected spot prices which are built on fundamental market expectations. In the following article the crucial impact parameters of forward electricity prices and the relationship between forward and future spot prices will be assessed by an empirical analysis of electricity prices at the European Energy Exchange and the Nord Pool Power Exchange. In fact, price formation in the considered markets is influenced by historic spot market prices yielding a biased forecasting power of long-term contracts. Although market and risk assessment measures of market participants and supply and demand shocks can partly explain the futures-spot bias inefficiencies in the analysed forward markets cannot be ruled out.     

Modelling and simulation of bottle rinsing

This study describes newly developed mathematical models of bottle rinsing. Our approach is based on 3D‐CFD models of turbulent two‐phase flow (water and air), which have been implemented based on the freely available open source software OpenFOAM. The models are validated using data obtained with a standard injection nozzle and then used to evaluate the performance of two fictitious modified nozzle types w.r.t. cleaning efficiency, water consumption and water drainage. Maps of the interior walls of the bottles showing the distribution of important parameters such as wall shear stresses or water coverage were derived from the simulations. The simulations suggest that rotating or pulsating injection nozzles may perform better than standard nozzle configurations.     

Two-Level Additive Schwarz Preconditioners for a Weakly Over-Penalized Symmetric Interior Penalty Method

We propose and analyze several two-level additive Schwarz preconditioners for a weakly over-penalized symmetric interior penalty method for second order elliptic boundary value problems. We also report numerical results that illustrate the parallel performance of these preconditioners.     

可优化加热炉控制的板坯在线测量技术

为了新加热炉的优化控制,掌握各个板坯的几何尺寸和重量数据是十分重要的.当然,可靠的板坯识别是使板坯能够按照预先设定的计划进行热处理的前提条件.为了获得所需的所有几何尺寸信息,在加热炉前方的辊道上,测量了板坯的厚度、宽度、长度以及厚度方向四面的轮廓尺寸.而且,还必须确定热装和冷装板坯的凸度、锥度和平直度.     

An international study on the importance of androstenone and skatole for boar taint: IV. Simulation studies on consumer dissatisfaction with entire male pork and the effect of sorting carcasses on the slaughter line, main conclusions and recommendations

An international study has been conducted in order to determine the respective contributions of androstenone and skatole to boar taint and their possible variations according to production systems and consumer populations. The presentation of the study and the main results concerning skatole and androstenone levels and data from sensory evaluation or consumer surveys are reported in companion papers. The present paper summarises the main conclusions of the study and gives tentative recommendations. A simulation study was conducted, based on the skatole and androstenone levels currently observed in European populations of entire male pigs and on the results of the consumer surveys. The first part of the simulation study demonstrated that, overall, 6.5% (odour) and 3.0% (flavour) more consumers were dissatisfied with entire male than with gilt pork. The differences were, however, very variable according to countries. Consumer dissatisfaction for the odour of entire male pork was mostly associated with high skatole levels, while androstenone had little influence on it. On the other hand, androstenone and skatole had similar contributions to the level of dissatisfaction for flavour. From the present study it is not possible to determine clear cut-off levels for androstenone/skatole. The regression equations presented in [Matthews, K. R., Homer, D. B., Punter, P., Béague, M. P., Gispert, M., Siret, F., Leask, H., Fonti i Furnols, M., & Bonneau, M. (2000). An international study on the importance of androstenone, skatole for boar taint: III. Consumer survey in seven European countries. Meat Science, 54, 271-283] provide a basis for decision making. However, due to methodological limitations, the results may underestimate consumer reaction to entire male pork. The second part of the simulation study demonstrated that sorting carcasses on the basis of androstenone/skatole would reduce, but not eliminate, differences in consumer dissatisfaction between entire male and gilt pork. For odour, taking androstenone into account did not improve the efficiency obtained from sorting using skatole only. For flavour, sorting using both compounds was more efficient than sorting using skatole only. Sorting out 15% of the entire males, on the basis of skatole only, would result in a difference in the proportion of dissatisfied consumers of 4.2% (odour) or 2.0% (flavour) between entire male and gilt pork. The results of the last part of the simulation study demonstrated that decreasing skatole in entire male pig populations, to levels as low as 0.10 ppm, would still result in a difference in the proportion of dissatisfied consumers of 3.2% (odour) or 1.6% (flavour). To reduce this difference further, the levels of both compounds would have to be reduced still further. The lowest difference that can be achieved is 2.3% (odour) or 0.4% (flavour). The conclusions of the present study may differ according to whether immediate commercial applications or long-term goals are considered. On the basis of the skatole and androstenone levels currently observed in entire male pig populations, sorting out procedures based on skatole is the easiest way to rapidly achieve a significant decrease in consumer dissatisfaction with entire male pork. In most countries, however, this will not be sufficient to obtain the same level of acceptability as with gilts. In the long term, a sharp reduction in both skatole and androstenone would have to be achieved in entire male pig populations to obtain low differences in acceptability between entire male and gilt pork.     

Influence of differences in sensitivity of Spanish and German consumers to perceive androstenone on the acceptance of boar meat differing in skatole and androstenone concentrations

The reactions of German (n=472) and Spanish (n=480) consumers of the European boar taint study to boar meat were evaluated according to their androstenone sensitivity. Consumers were checked with pure substance for their androstenone sensitivity. Eighteen per cent of the German and 31% of the Spanish participants were highly sensitive to androstenone, with a significantly higher proportion of women. For insensitive/mildly sensitive consumers, skatole level was the main determinant for the rating of flavour and odour of pork. For highly sensitive consumers, androstenone significantly influenced the rating of odour (Spain and Germany) and flavour (Germany) and is the predominant problem for that group, due to the high percentage of carcasses with high androstenone levels.     

An international study on the importance of androstenone and skatole for boar taint: I. Presentation of the programme and measurement of boar taint compounds with different analytical procedures

An international study, involving 11 participants in 7 European countries, was conducted to provide scientific evidence for an objective measurement of boar taint in entire male pigs and its possible variation between countries. The specific objectives were to determine the respective contributions of androstenone and skatole to boar taint and their possible variations according to production systems and consumer populations. Over 4000 entire male pigs and 200 gilts were raised and slaughtered in 6 countries. Meat samples were taken from the loin and backfat samples were used for the rapid measurement of androstenone and skatole. A sub-population of 377 entire males and 42 gilts was then selected in such a way as to represent all combinations of skatole and androstenone levels. Androstenone and skatole levels in the selected samples were checked, using established reference methods. Meat samples from the selected animals were used for sensory evaluation by trained panels and for consumer surveys in 7 European countries. The present paper gives a general presentation of the programme and reports the main characteristics of the samples. Three companion papers present the results of the evaluation by trained sensory panels [Dijksterhuis, G., Engel, B., Walstra, P., Font i Furnols, M., Agerhem, H., Fisher, K., Oliver, M. A., Claudi-Magnussen, C., Siret, F., Béague, M. P., Homer, D. B., & Bonneau, M. (2000). An international study on the importance of androstenone and skatole for boar taint: II. Sensory evaluation by trained panels in seven European countries. Meat Science54, 261-269], the results of the consumer surveys [Matthews, K. R., Homer, D. B., Punter, P., Béague, M. P., Gispert, M., Kemspter, A. J., Agerhem, H., Claudi-Magnussen, C., Fischer, K., Siret, F., Leask, H., Font i Furnols, M., & Bonneau, M. (2000). An international study on the importance of androstenone and skatole for boar taint: III. Consumer survey in seven European countries. Meat Science, 54, 271-283] and the main conclusions and recommendations [Bonneau, M., Walstra, P., Claudi-Magnussen, C., Kempster, A. J., Tornberg, E., Fischer, K., Diestre, A., Siret, F., Chevillon, P., Claus, R., Dijksterhuis, G., Punter, P., Matthews, K. R., Agerhem, H., Béague, M. P., Oliver, M. A., Gispert, M., Weiler, U., von Seth, G., Leask, H., Font i Furnols, M., Homer, D. B., & Cook, G. L. (2000). An international study on the importance of androstenone and skatole for boar taint: IV. Simulation studies on consumer dissatisfaction with entire male pork and the effect of sorting out carcasses on the slaughter line, main conclusions and recommendations. Meat Science, 54, 285-295]. Seasonal effects and differences between countries in skatole and androstenone levels are presented elsewhere [Walstra, P., Claudi-Magnussen, C., Chevillon, P., von-Seth, G., Diestre, A., Matthews, K. R., Homer, D. B., & Bonneau, M. (in press). An international study on the importance of androstenone and skatole for boar taint: Levels of androstenone and skatole according to country and season. Livestock Production Science]. A supplementary paper considers the effects of human sensitivity to androstenone and skatole on the consumer acceptance of entire male pork [Weiler, U., Font i Furnols, M., Fischer, K., Kemmer, H., Oliver, M. A., Gispert, M., Dobrowolski, A., & Claus, R. (in press). Influence of differences in sensitivity of Spanish and German consumers to perceive androstenone on the acceptance of boar meat differing in skatole and androstenone concentrations. Meat Science]. A study of possible other compounds contributing to boar taint was also carried out within this programme.     

Effect of dietary levels of fat, α-tocopherol and astaxanthin on colour and lipid oxidation during storage of frozen rainbow trout (Oncorhynchus mykiss) and during chill storage of smoked trout

 Female rainbow trout (Oncorhynchus mykiss) with an initial weight of 0.8–0.9 kg were raised in two experiments including a total of 2550 fish divided into 17 groups. The fish were raised for 6 months on 13 different feeds (four fish groups were replicates) varying in dietary levels of fat (27% or 32%), astaxanthin (40, 70 or 100 mg astaxanthin/kg feed) and vitamin E (α-tocopherol; 100, 300 or 600 mg all-rac-α-tocopheryl acetate/kg feed). The levels of fat, astaxanthin and α-tocopherol in the fillets all increased with increasing dietary levels of each feed component. Furthermore, astaxanthin deposition was found to be significantly improved by increasing the dietary fat level from 27% to 32%, but was not affected by dietary levels of α-tocopherol. The highest deposition of α-tocopherol was found in fish fed the lowest level of astaxanthin (40 mg/kg), whereas α-tocopherol deposition was unaffected by the dietary fat level. Frozen storage (–28  °C) of gutted, cleaned and glazed raw fish for 18 months significantly reduced astaxanthin and α-tocopherol levels, while lipid oxidation, measured as thiobarbituric acid reactive substances (TBARS) was limited. In the first experiment, the highest TBARS levels were found during frozen storage in fish fed the lowest level of astaxanthin (40 mg/kg versus 70 mg/kg or 100 mg/kg); unaffected by dietary levels of α-tocopherol (100 mg/kg versus 600 mg/kg), whereas the dietary astaxanthin level (70 mg/kg versus 100 mg/kg) did not influence lipid oxidation in frozen fish in the second experiment. After brine injection, fillets of fish were smoked and a vacuum-packed (95%), sliced product in a transparent laminate was produced. The quality (pigmentation and lipid oxidation) during 3 weeks of illuminated, chill storage (3  °C) was compared for smoked products produced from fresh fish and from fish stored at –28  °C for 12 months and 18 months. Smoked fillets from fish fed 32% fat were found to be less red than those from fish fed 27% fat, and the astaxanthin content and surface redness of the smoked product decreased during chill storage. Lipid oxidation was pronounced in smoked trout, but a high level of α-tocopherol in the fillet significantly reduced lipid oxidation during chill storage of the smoked product. Lipid oxidation in smoked fillets from fish fed 32% fat was more pronounced than in fish fed 27% fat, but increasing the dietary α-tocopherol level from 300 mg/kg feed to 600 mg/kg feed effectively counteracted the negative effect of the high-fat diet on lipid oxidation in the smoked product. Astaxanthin did not affect lipid oxidation in the chill-stored smoked product, in contrast to the frozen, raw fish. Astaxanthin seems to protect against the very early stages of lipid oxidation, while α-tocopherol is more important as an antioxidant at more advanced stages of lipid oxidation. Received: 8 January 1998 / Revised version: 23 March 1998     

Design of geothermal steam supply systems in Iceland

The role of the geothermal steam supply system is to receive the geothermal fluid from the geothermal wells, separate the steam from the water and to deliver steam and/or water to a user of the thermal energy. It may be for direct use in any kind of an industrial process, such as drying, heating, cooling, etc., or it may be intended for electric power generation. The steam supply system delivers the fluid at a specified temperature, pressure and quality to the user.The steam supply system consists of wellheads, steam collection pipelines, nowadays in Iceland normally designed for two-phase flow of water and steam, steam-water separators, main steam/water lines, moisture separators, control valves, exhaust system, and effluent disposal equipment as needed and may include compressors and/or pumps for long distance transportation.Design criteria for the system depend on one hand upon the characteristics of the geothermal field, and on the other upon the intended use and required steam quality and economy. High enthalpy fields, for example, are capable of producing high pressure steam which is relatively economical when electric power generation alone is being considered. For such systems, high quality of the steam is of utmost importance.The paper gives a general overview of the steam supply systems in Iceland and describes the main features of the Nesjavellir steam supply system where the main emphasis was laid on high steam quality in order to prevent scaling in turbines, control valves and heat exchangers. New systems or systems needing restoration should be based on the same features.     

Nanowire Arrays: Intact Mammalian Cell Function on Semiconductor Nanowire Arrays: New Perspectives for Cell‐Based Biosensing (Small 1/2011)

Nanowires (NWs) are attracting more and more interest due to their potential cellular applications, such as delivery of compounds or sensing platforms. Arrays of vertical indium‐arsenide (InAs) NWs are interfaced with human embryonic kidney cells and rat embryonic dorsal root ganglion neurons. A selection of critical cell functions and pathways are shown not to be impaired, including cell adhesion, membrane integrity, intracellular enzyme activity, DNA uptake, cytosolic and membrane protein expression, and the neuronal maturation pathway. The results demonstrate the low invasiveness of InAs NW arrays, which, combined with the unique physical properties of InAs, open up their potential for cellular investigations.