[en] The effective stress concept was defined by Terzaghi in 1923 and was introduced 1936 in a conference at Harvard University. The concept has under a long time been used in soil mechanics to analyse deformations and strength in soils. The effective stress σ' is equal to the total stress σ minus the pore pressure u (σ'=σ-u). The concepts's validity in a jointed rock mass has been investigated by few authors. A literature review of the area has examined many areas to create an overview of the use of the concept. Many rock mechanics and rock engineering books recommend that the expression introduced by Terzaghi is suitable for practical purpose in rock. Nevertheless, it is not really clear if they mean rock or rock mass. Within other areas such as porous rocks, mechanical compressive tests on rock joints and determination of the permeability, a slightly changed expression is used, which reduces the acting pore pressure (σ'=σ-α·u). The α factor can vary between 0 and 1 and is defined differently for different areas. Under assumption that the pore system of the rock mass is sufficiently interconnected, the most relevant expression for a jointed rock mass, that for low effective stresses should the Terzagi's original expression with α=1 be used. But for high normal stresses should α=0.9 be used

[en] This is the final report under Agreement No E/5A/163/2803, concerning the comparison of Hot Dry Rock (HDR) economic cost studies - the cost modelling approaches, the calculation methods and the assumptions. The work has been reported in two parts as follows: economics of HDR systems - main report; review of HDR drilling and stimulation costs - sub-contractor report. (author)

[en] An approach to the control of the sizes of oxide and metal nanoparticles produced in solutions is presented. It is assumed that a key point is the spontaneous formation of neutral hydroxo complexes usually containing 24 metal atoms. Their progressive development is either further self-assembly with the formation of particles of various-dimensions or functioning as heteroepitaxial nuclei in the formation of nanoparticles with a different composition

[en] The paper proposes a model to represent medium-term hydro-thermal operation of electrical power systems in deregulated frameworks. The model objective is to compute the oligopolistic market equilibrium point in which each utility maximises its profit, based on other firms' behaviour. This problem is not an optimisation one. The main contribution of the paper is to demonstrate that, nevertheless, under some reasonable assumptions, it can be formulated as an equivalent minimisation problem. A computer program has been coded by using the proposed approach. It is used to compute the market equilibrium of a real-size system. (author)

[en] Yanshan-Liaoning area is located in the east part of the northern margin of North-China platform. It is a famous metallogenic region of Mesozoic volcanic hydrothermal type U-Au-polymetallic deposits in the country. The metallogenesis is controlled by a united Late Mesozoic continental taphrogenic volcano-magmatic activity. The metallogenic epochs are concentrated in Late Jurassic-Early Cretaceous periods. The metallogenic media are moderate and moderate-low temperature volcanic hydrothermal solutions originated from the mixing of volcano-magmatic water, metamorphic water and atmospheric water. The ore-forming materials are mainly derived from enrichment type upper mantle and lower crust. (8 refs., 5 figs.)

[en] A cost benefit model for the economic evaluation of HDR energy production cost was developed. It can be used for systematic cost analyses of different components of a HDR plant. This relates to natural subsurface conditions (i.e., geothermal gradient, tectonic stress) as well as technical components (i.e., boreholes, heat/power conversion system). The model provides the limiting conditions for an economic HDR energy production. The economic model was applied for an evaluation of the natural parameters in the subsurface of Germany regarding their HDR-suitability. Within a site selection program in Europe the model is part of feasibility studies for the conceptual design of a HDR demonstration plant at three candidate sites: Bad Urach (Germany); Soultz-sous-Forets (France) and Cornwall (UK)

[en] A detailed and comprehensive cost model for Hot Dry Rock (HDR) electricity producing systems has been developed in this study. The model takes account of the major aspects of the HDR system, parameterized in terms of the main physical and cost parameters of the resource and the utilization system. A doublet configuration is assumed, and the conceptual HDR system which is defined in the study is based upon the UK Department of Energy (DEn) HDR geothermal R and D programme. The model has been used to calculate the costs of HDR electricity for a UK defined base case which represents a consensus view of what might be achieved in Cornwall in the long term. At 14.2 p/kWh (1988 costs) this cost appears to be unacceptably high. A wide-ranging sensitivity study has also been carried out on the main resource, geometrical, and operational parameters of the HDR system centred around the UK base case. The sensitivity study shows the most important parameters to be thermal gradient and depth. (Author)

[en] This article examines the practical perspective for introducing the deregulation model in systems with a strong predominance of hydroelectric generation, such as the Brazilian electricity system. In order to do this, the article describes the process of establishing short-term prices in systems with such characteristics, concluding that this economic signal is inefficient for stimulating a sustained generation expansion. As a result of this analysis, the article proposes, as a regulatory policy, a competitive process of energy contracting that favors the making of decisions with long-term horizons, ensuring the adequacy of supply, and, additionally, permitting a satisfactory management of market risk by generation and distribution companies

[en] With increasing attention paid to energy and environment in recent years, the hydrothermal scheduling considering economic and environmental objectives is becoming one of the most important optimization problems in power system. With two competing objectives and a set of operation constraints, the economic environmental hydrothermal scheduling problem is classified as a typical multi-objective nonlinear constrained optimization problem. Thus, in order to efficiently resolve this problem, the multi-objective quantum-behaved particle swarm optimization (MOQPSO) is presented in this paper. In MOQPSO, the elite archive set is adopted to conserve Pareto optimal solutions and provide multiple evolutionary directions for individuals, while the neighborhood searching and chaotic mutation strategies are used to enhance the search capability and diversity of population. Furthermore, a novel constraint handling method is designed to adjust the constraint violation of hydro and thermal plants, respectively. In order to verify its effectiveness, the MOQPSO is applied to a classical hydrothermal system with four hydropower plants and three thermal plants. The simulations show that the proposed method has competitive performance compared with several traditional methods. - Highlights: • Multi-objective quantum-behaved particle swarm optimization is proposed. • Mutation and neighborhood search enhance the population diversity. • Constraints handling method improves the feasibility of individuals. • MOQPSO obtains better solutions with less fuel cost and emissions.

[en] This paper proposes a hybrid method combining differential evolution (DE) and sequential quadratic programming (SQP) for solving short term hydrothermal scheduling problem with non-convex fuel cost function. In this paper, differential evolution (DE) is used as a global optimizer and sequential quadratic programming (SQP) method as a local optimizer to fine tune the solution. The proposed method has been tested on a multichain cascaded reservoir with an equivalent thermal test system and the simulation results are compared with existing methods reported in literatures. From the results, it clearly shows that the proposed method is giving better quality solutions than existing methods.