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An approach for solving reactive power planning problems is presented, which is based on binary search techniques and the use of a special heuristic to obtain a discrete solution. Two versions were developed, one to run on conventional (sequential) computers and the other to run on a distributed memory (hypercube) machine. This latter parallel processing version employs an asynchronous programming model. Once the set of candidate buses has been defined, the program gives the location and size of the reactive sources needed (if any) in keeping with operating and security constraints. Keywords: Reactive Power Planning; Parallel Processing; Binary Search; Heuristic Methods

This paper describes the implementation of a Monte Carlo based short-circuit analysis package in a hypercube parallel computer. The program generates accurate estimates of short-circuit current probability distribution curves which can be used in a variety of planning and design studies. Both network modeling aspects, such as network reduced equivalencing and mutual coupling representation, as well as the impact of the sample sizes used in Monte Carlo simulations are fully analyzed and illustrated by numerical results obtained testing on real-world systems. These examples clearly illustrate how computational efficiency in parallel machines varies with the ratio of communication to computation (communication overhead) and of the load balancing among the parallel computer processors.

Observability analysis based exclusively on topological information may lead to systems whose state cannot be estimated by regular state estimation methods. This paper discusses some practical situations in which the presence of the so called discardable measurements may pass undetected by topological observability analysis. As a consequence, wrong results, or even convergence problems, may occur. A numerically based observability analysis procedure is suggested for handling such cases; the new technique is an extension of previously published work on numerical observability analysis. The technique is fully illustrated by small scale examples taken from a real-life system where difficulties with discardable measurements have been observed.

FIDASIM is a code that models signals produced by charge-exchange reactions between neutrals and ions (both fast and thermal) in magnetically confined plasmas. With the ion distribution function as input, the code predicts the efflux to a neutral particle analyzer diagnostic and the photon radiance of Balmer-alpha light to a fast-ion D diagnostic, in addition to many other related quantities. A new, parallelized version of the Monte Carlo code FIDASIM has been developed in Fortran90 that is substantially faster than the original interactive data language version. Modified algorithms include more accurate treatments of the time dependent collisional-radiative equations that describe neutral energy levels, of the cloud of 'halo' neutrals that surround the injected neutral beam, and of finite Larmor radius effects. Enhanced physics capabilities include modelling 'passive' signals from cold edge neutrals, the ability to treat general three-dimensional magnetic confinement configurations, and calculations of diagnostic-specific weight functions that enable tomographic reconstructions of the fast-ion distribution function. Neutral beam attenuation, beam emission, and fast-ion birth profiles are also modelled. The new algorithms have been successfully validated against experimental data and new features have been tested through benchmarks between two independently developed versions of the code. [ABSTRACT FROM AUTHOR]

Understanding the effect of Alfvén eigenmodes (AEs) and neoclassical tearing modes (NTMs) on fast ions is highly important for fusion reactors due to potentially strong resonant interactions between the fast ions and the modes. Here, we use the four-view fast-ion D-alpha (FIDA) diagnostic installed in the DIII-D tokamak to reconstruct the fast-ion velocity distribution at two radial positions during two sequential discharges with strong and weak mode activity, respectively. The velocity-space coverage of the diagnostics, however, only allows reliable reconstructions of fast ions with positive pitches. Therefore, we suggest new tomographic inversion methods relying on prior information outside the well-diagnosed region. We find that within the population of fast ions with positive pitches, ions, at all energies, are transported away from the measurement volumes. Comparisons between the reconstructions and kick model simulations, where the mode activity is considered, reveal that low-frequency modes such as the NTMs and low-frequency AEs contribute significantly to the positive-pitch fast-ion transport in the central measurement volume, whereas TAEs and EAEs become important farther out and are responsible for decreased fast-ion confinement. [ABSTRACT FROM AUTHOR]

• Discontinuities in rocks – from microcracks to fractures and faults – couple effective thermal conductivity to stress, and fluid conditions. • The apparent thermal discontinuity across fractures called thermal contact resistance arises from heat flow constriction at contacts, phonon scattering, and the low thermal conductivity of interstitial fluids. • Our contact mechanics-inspired inverse power function models the change in thermal contact resistance with stress. • Water reduces the thermal contact resistance by nearly 70% for clean and gouge-filled fractures. • The rock mass effective thermal conductivity can be estimated from intact rock thermal conductivity measurements and the assessment of the thermal contact resistance of a single fracture in the lab. The thermal conductivity of fractured rock masses is an important parameter for the analysis of energy geosystems, yet, its measurement is challenged by specimen size requirements. Fluids within fractures have lower thermal conductivities than rock minerals and heat flow lines constrict through contacting asperities. Together, heat flow constriction and phonon boundary scattering cause an apparent temperature discontinuity across the fracture, typically represented as a thermal contact resistance. We investigate the thermal contact resistance in fractured limestone and its evolution during loading and unloading (σ'=10 kPa to σ'=3000 kPa) for clean and gouge-filled fractures, under both air-dry and water-saturated conditions. The fracture thermal contact resistance decreases during loading because of the increase in the true contact area, gouge and asperity crushing, and fracture filling by produced fines that contribute new conduction pathways. These processes convey high stress sensitivity and loading hysteresis to the fracture thermal contact resistance. Water fills the fracture interstices and forms menisci at mineral contacts that significantly improve heat conduction even in partially saturated rock masses. The rock mass effective thermal conductivity can be estimated by combining the intact rock thermal conductivity with measurements of the thermal contact resistance of a single fracture under field boundary conditions. [ABSTRACT FROM AUTHOR]