Results 1 - 10 of 1869
Results 1 - 10 of 1869. Search took: 0.025 seconds
|Sort by: date | relevance|
[en] Factors that over the past 20 years brought about changes in the dynamics of the fuel and power demand in industrial countries are analyzed. These changes mirror long-term trends of restructuralization of economics of these countries. The overall energy situation is described based on statistical data of the UNO Economic Commission for Europe as of 1987. Attention is also paid to the ecological aspects of the development of the power industry and to the economic impacts of ecological requirements. (Z.M.). 8 refs
[en] In the study, 6082 Al and 7075 Al samples were subjected to a solution taking place at 580 °C for 1 min using ultrahigh frequency induction heating system (UHFIHS) and water was supplied at the end of the process. Artificially aging was then carried out at 190 °C for 2, 4, 6 and 8 min. In both applications, heating was carried out using an induction system with a frequency of 900 kHz and a power of 2.8 kW. For these aluminum series and shapes, induction heating and heat treatment costs in different shapes are calculated. In addition, the hardness values obtained from artificially aged 6082 Al and 7075 Al samples at 190 °C for 10 h were compared with conventional methods after 5 h at 540 °C for 5 h. As a result, the hardness values of 6082 Al samples, which were obtained in 10 h by conventional methods, were obtained by artificial aging for only 8 min using induction system.
[es]Muestras de las aleaciones 6082 A1 y 7075 A1 se sometieron a un tratamiento térmico en horno de inducción de ultraalta frecuencia (UHFIHS) a 580 ºC durante 1 min y suministro de agua al final del proceso. El envejecimiento artificial se llevó a cabo a 190 °C durante 2, 4, 6 y 8 min. En ambas aplicaciones, el calentamiento se llevó a cabo utilizando un sistema de inducción con una frecuencia de 900 kHz y una potencia de 2,8 kW. Para estas series y diseños de aluminio, se calcularon los costos del tratamiento térmico. Adicionalmente, se compararon los valores de dureza de las muestras de 6082 A1 y 7075 A1 envejecidas artificialmente a 190 °C durante 10 h con los métodos convencionales 540 °C durante 5 h. Los resultados de dureza de la muestra 6082 Al obtenidos en 10 h mediante métodos convencionales, tardaron sólo 8 min mediante el envejecimiento artificial con el sistema de inducción.
[en] Taking a comprehensive approach, the book presents the energy issue in a global context, discussing both the scientific and technical and the socio-economic perspectives. Terms such as fossil energy sources, nuclear power, renewable energy sources, environmental impacts and the global climate, risk analysis and acceptability, energy conservation, economic and regulatory framework conditions and strategies broadly characterize the manifold aspects discussed in this book. (DG)
[de]Das Buch stellt die wissenschaftlich-technischen wie auch die oekonomisch-gesellschaftlichen Perspektiven des Energieproblems in einen groesseren Zusammenhang. Fossile Energieversorgung, Kernenergie, umweltvertraegliche erneuerbare Energien, Umweltbelastung und das globale Klimaproblem, Risikofragen, Energiesparen sowie wirtschaftliche und ordnungspolitische Rahmenbedingungen und Muster werden hierbei angesprochen. (DG)
[en] In general, the developing countries due to changes in supply and demand for energy in the world, are facing several problems, such as: 1. Energy growth. 2.Energy consumption 3.Environmental protection. The objective of this paper is to study the problems caused by the increase in the energy consumption of the developing countries. also several guideline and solution schemes are recommended for these problems
[en] This paper selects stochastic volatility (SV) as the uncertainty or volatility measure to re-examine the Samuelson hypothesis of maturity effect (SHME) (Samuelson, 1965). Stochastic dominance is used to examine whether the stochastic volatility level dominates with respect to maturity. The empirical analyses of energy-futures price series generally provide mild support for this hypothesis in terms of the first two degrees of stochastic dominance. Each type of futures has its own properties with respect to the maturity effect. SV levels play a role in determining the testing outcome. The hypothesis is more likely to hold at low SV levels. The higher the volatility level, the less likely the SHME will hold because SV surges to its peak level regardless of maturity. - Highlights: • This paper selects stochastic volatility (SV) as the uncertainty or volatility measure to re-examine the Samuelson hypothesis. • Stochastic dominance is employed to examine if the SV level dominates with respect to maturity. • Energy futures price series give mild support to this hypothesis in terms of the first two orders of stochastic dominance. • The hypothesis is more likely to hold at low SV levels. • The higher the volatility level, the less likely the hypothesis will hold because SV surges to its peak level regardless of maturity.
[en] This presentation dealt with methods for assessing commodity price risk in an asset transaction; the setting of risk management objectives; building hedging into the financing; and internal reporting and accounting to mitigate trading risks. It also provided some recent examples of successful hedging in gas asset transactions. The objectives of risk management and the nature of hedging and speculation were explored. An approach to price risk management was proposed. The development of price risk management tools, and techniques for managing risks involving interest rates, foreign exchange, and commodities were examined. figs
[en] This paper contributes to the commodity pricing literature by consistently modeling the convenience yield with its empirically observed properties. Specifically, in this paper, we show how a four-factor model for the stochastic behavior of commodity prices, with two long- and short-term factors and two additional seasonal factors, may accommodate some of the most important empirically observed characteristics of commodity convenience yields, such as the mean reversion and stochastic seasonality. Based on this evidence, a theoretical model is presented and estimated to characterize the commodity convenience yield dynamics that are consistent with previous findings. We also show that commodity price seasonality is better estimated through convenience yields than through futures prices. - Highlights: • Energy commodity convenience yields exhibit mean reversion and stochastic seasonality. • We present a model for convenience yields accounting for their observed characteristics. • Commodity price seasonality is better estimated through convenience yields