Effect of longwall face advance rate on spontaneous heating process in the gob area - CFD modelling

A commercial CFD software programme, FLUENT, was used to study the oxidation process of coal in the mined-out longwall (gob) area. A three-dimensional, single-phase model with a continuously advancing longwall face has been developed. For the model, the gob longwall area was designed on the basis of the actual longwall panel operating in the Ostrava-Karviná Coal Mines (OKD, Czech Republic). The behaviour of the coal to oxygen was modelled using the results arising mainly from the former laboratory-scale experiments with Czech bituminous coals. Basically, the technique of pulse flow calorimetry and measurements at a continuous airflow reactor were applied during the laboratory investigations. In the contribution, the main focus was to understand the effect of the longwall face advancing speed on the oxidation heat production as well as evolution of the gases in the gob area. Simultaneously, the effect of coal crushing in the mined-out area on the spontaneous heating process was examined.Numerical simulations confirmed the existence of a “favourable” zone for the onset and development of the spontaneous heating process in the gob area. The location and the maximal temperature reached in the “favourable” zone were found to be significantly affected by the advancing rate of the coalface. The slower the advancing rate is, the higher the maximal temperature and smaller the depth of the “favourable” zone in the gob area are. When the rate drops to a certain “critical” value, spontaneous heating turns to flammable combustion of the coal. The value of the “critical” advancing rate was confirmed to increase if the grain size of the coal left in the gob decreases. Numerical examinations of carbon monoxide concentrations then proved that small incidents of spontaneous heating could occur in the gob area that need not be detected in the airflow of the longwall tail gate.     

Inhomogeneous structure of near-surface layers in the ion-implanted NiTi alloy

This paper reports the application of nitrogen ion implantation for modification of a shape memory alloy. It is known that the problem of creating a protective surface coating for the shape memory alloy is the most acute for potential applications of this material. Thus, the problem of increasing surface protective properties and, at the same time, simultaneous preservation of functional properties of shape memory materials is a subject of research and development [Pelletier H, Muller D, Mille P, Grob J. Surf Coat Technol 2002;158:309.]. The surface characterization of nitrogen implanted (fluence 10¹⁸ cm^?2 and energy 50 keV) equiatomic commercial NiTi alloy samples was performed with the assistance of high resolution transmission electron microscopy (HTEM) techniques and modifications of phase composition before and after irradiation are studied at room and martensitic transformation temperatures by X-ray diffraction methods. Differential scanning calorimetry (DSC, TA Instruments) was used to characterize the transformation sequence and transformation temperatures for the initial and surface-modified materials. Experimental results of an inhomogeneous structure of near-surface layers in the ion-implanted NiTi alloy are discussed in this paper.     

Brief coping skills treatment for cocaine abuse: substance use outcomes at three months

AIMS: Coping skills training, a promising treatment approach for alcoholics, was adapted for use with cocaine abusers and effects on outcome were investigated. DESIGN: A cocaine-specific coping skills training (CST) package was compared to an attention placebo control when both were added to a comprehensive treatment program. SETTING: The sites were two private substance abuse treatment facilities, one residential and rural, and one an urban partial hospital. PARTICIPANTS: Substance abusers in treatment with cocaine abuse or dependence were selected. INTERVENTION: The CST intervention was conducted in individual sessions. It involved functional analysis of high risk situations and coping skills training based on the functional analysis. FINDINGS: Clients who received CST had significantly fewer cocaine use days and the length of their longest binge was significantly shorter during the 3-month follow-up period compared to clients in the control condition. CST did not affect relapse rates or use of other substances. CONCLUSIONS: Results support the notion that cocaine-specific CST is a promising adjunct to treatment for cocaine abusers.     

Turbulence triggers vigorous swimming but hinders motion strategy in planktonic copepods

Calanoid copepods represent a major component of the plankton community. These small animals reside in constantly flowing environments. Given the fundamental role of behaviour in their ecology, it is especially relevant to know how copepods perform in turbulent flows. By means of three-dimensional particle tracking velocimetry, we reconstructed the trajectories of hundreds of adult Eurytemora affinis swimming freely under realistic intensities of homogeneous turbulence. We demonstrate that swimming contributes substantially to the dynamics of copepods even when turbulence is significant. We show that the contribution of behaviour to the overall dynamics gradually reduces with turbulence intensity but regains significance at moderate intensity, allowing copepods to maintain a certain velocity relative to the flow. These results suggest that E. affinis has evolved an adaptive behavioural mechanism to retain swimming efficiency in turbulent flows. They suggest the ability of some copepods to respond to the hydrodynamic features of the surrounding flow. Such ability may improve survival and mating performance in complex and dynamic environments. However, moderate levels of turbulence cancelled gender-specific differences in the degree of space occupation and innate movement strategies. Our results suggest that the broadly accepted mate-searching strategies based on trajectory complexity and movement patterns are inefficient in energetic environments.     

An indirect approach for evaluating the availability of adjustablespeed drive systems applied to large power plant motors

Concerns may exist about the availability of adjustable speed drive (ASD) systems applied to large fixed speed motors at power plants. AEP has very limited experience with ASDs. Different data sources, including AEP fixed speed motor failure statistics, AEP's survey on utility experience with ASDs, NERC data, and manufacturers' data were used. This paper demonstrates that all estimates result in consistently high levels of availability for ASDs     

Announcements on the PES Web Site

The conversion of a one-player power sector (i.e., a natural monopoly) into a multiple-players power market brings not only benefits of competition but also the costs of complexity to the consumers. Between the two, an optimal number of players is found, corresponding to the minimum price of power to the consumers. Considering time as the third dimension, the optimum curve becomes a potential surface on which the evolution of the market entities is seen as oscillations (mergers and unbundling) along the valley of minimum price. Every oscillation triggers a price burst, which is detrimental to the consumers. To avoid this, the role of the regulator is better defined in the sense of smoothing the transition from monopoly to market. The example of the US and of the EU power sectors' evolution is relevant here. In the above approach, long-range competition resulting from the future opening of power markets in Europe or from the penetration, 70 years ago, of the interconnection technology in the USA, is compared with the short-range (local) competition.     

Brief coping skills treatment for cocaine abuse: 12-month substance use outcomes.

Patients (N?=?108) in a study of cocaine-specific coping skills training (CST), which was found to reduce cocaine use during a 3-month follow-up, were followed for an additional 9 months. CST involved coping skills training in the context of high-risk situations. Control treatment used meditation-relaxation. Both were added to comprehensive private substance abuse treatment. Patients in CST who relapsed had significantly fewer cocaine use days than did the control group during the first 6 months, then both conditions did equally well. Patients in CST also drank alcohol more frequently in the last 6 months than did contrast patients but did not differ in heavy drinking days. For cocaine use outcomes, no interaction of treatment was found with gender, education, route of administration, drug use severity, sociopathy, or depression. Implications include the need to investigate different lengths and combinations of treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of phosphorylation of the maize starch on thermal generation of stable and short‐living radicals

Effect of hydrolysis, phosphorylation and treatment with high hydrostatic pressure on thermal generation of stable and short‐living radicals in maize starch was studied by X‐ray diffraction (XRD), electron paramagnetic resonance (EPR) spectroscopy, differential scanning calorimetry and polarized light microscopy. Phosphorus was introduced into maize starch as mono‐ and distarch phosphates. XRD indicated localization of phosphate groups in amorphous part of the granule whereas calorimetric data suggested some cross‐linking of the distarch phosphates. Stable and short‐living radicals with unpaired electron localized at carbon atom were generated in all investigated samples in the temperature range commonly used for processing food. The number of detected short‐living radicals, stabilized by a spin trap, is of two orders of magnitude greater than that of the stable radical species. Hydrolysis and phosphorylation strongly increase the number of stable radicals while pretreatment of the starch with high hydrostatic pressure diminishes their amount. The EPR spectra of stable radicals consist of two components, single line and another one with hyperfine structure, indicating interaction of unpaired electron with neighboring hydrogen atom. The EPR spectra of the spin trap adducts with short‐living radicals contain three components from species differing in their dynamic properties depending on localization in zones of various degree of crystallinity.