Assessment of Hillside Coal Waste Embankment Failures Using Qualitative Analysis

Qualitative assessment provides a sound process for defining specific aspects of risk associated with potentially unstable slopes. Field observations, experience, field data, and back analysis from eleven past slope failures have been used to identify common and significant factors associated with the potential failure of coal waste embankments located in southwest Virginia. A database containing information about site location, characteristics, and conditions has been developed using Office of Surface Mining program narratives and engineering reports. It was observed that the pattern of failure was almost identical at each site and driven by the same phenomena. Degradation of the spoil material, accelerated by poor drainage conditions and periods of increased precipitation, lead to a decrease in interparticle strength and failure along a “lubricated,” or highly weathered, surface. The development of a rating system for the identification of potentially unstable coal waste embankments, based on the factors and characteristics reviewed here, will eventually lead to the implementation of a preventive maintenance program. Preventative maintenance will most likely need to include monitoring of the area, installation of a proper drainage system, and revegetation.     

Bed Sediment Characteristics in the Paraná and Paraguay Rivers

ABSTRACT

This paper presents a granulometric characterization of the Paraná and Paraguay rivers bed sediments. Samples obtained along 2,900 km of the thalweg of those rivers form the basis of this study. The main results and other features of the study are as follows: a) the bed sediment of both rivers is composed mainly of medium to fine well-sorted sands, with sizes in the Paraná slightly higher than those in the Paraguay river; b) the variations of mean diameters for both rivers are well correlated with the energy slopes. The correlation coefficient in the Paraguay river increases notably if the discharge and width/depth relationship variations along the channel are included in the regression; and, c) the origin of the transported sands could be related to the geologic characteristics of the Paraná river basin. An explanation is also suggested for the different bed sediment texture found in the Paraná de las Palmas and Paraná Guazú rivers in the lower delta. The explanation is based on the geomorphic processes that built that region of the Paraná river.     

Changes of the main physical and technological properties of talc due to mechanical strain

A commercial talc was treated by planetary ball milling to evaluate the changes of the main physical and technological properties due to induced progressive mechanical stress.Firstly, a high orientation of talc platelets was obtained, secondly a progressive structural disorder of the talc and finally a re-aggregation of the particles during prolonged grinding was observed. Delamination during the initial and intermediate stages cannot be excluded.Mechanical grinding reduced the particles size and increased the specific surface area leading to enhanced absorption and cation exchange capacity during the initial and intermediate stages of grinding. The reduced lightness and brightness for prolonged grinding were attributed to the agglomeration of the particles. The mechanical treatment does not induce significant amorphization, thus preserving the main properties of talc even after prolonged grinding.     

Partial user-supplied information and user modeling for improving QoS

The incorporation of user-supplied information has become mandatory for the improvement of QoS in network systems. There is the question about accommodation of new users of a service, given that information about former users of a service is available. In the present work, we followed two approaches to derive information about new users in the network design and control processes, where both are based on prototype generation for the answers of former users to a QoS related questionnaire. In the first approach, attempts were made to map user attributes to prototypes. The second approach used a mapping from partial answers to a prototype. As a result, the first approach appeared to be infeasible, while the second showed good results. In the resulting trade-off between number of prototypes and classification accuracy, it is possible, for example, with 8 prototypes for around 1000 users to predict the answers of new users by using only 30% of the answers of former users, while reducing accuracy by only 13% at the same time.     

Evidence for a double doping regime in Nd:YAG nanopowders

Nanopowders of Yttrium Aluminium Garnet doped with neodymium (Nd:YAG) were investigated by X-Ray Absorption Fine Structure (XAFS) at the Nd L_III edge in the 1.3–20.8% doping range. XANES spectra appear similar in the full range of the Nd concentration. However, a significant decrease in the white line intensity of XANES is revealed as the quantity of Nd doping ions increases. Plotting the white line intensity as a function of Nd doping ions reveals two linear trends with two different slopes, identifying a threshold value where the neodymium concentration reaches 5 at.% This experimental finding provides support for the existence of a double doping regime in Nd:YAG nanopowders. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Analysis of general multi-channel planar waveguides

Using the planar waveguide concept in surface acoustic wave (SAW) technology is often advantageous when the modeling of transversely distributed phenomena is indispensable for an accurate design of SAW devices. This is especially true when complex multi-track structures such as transversely coupled resonator filters (TCRFs) are under consideration where, e.g., transverse velocity and stiffness profiles have to be incorporated in the device simulation. The interdigital transducers (IDTs) and the reflector gratings composing those devices behave as planar waveguides, supporting, in principle, all kinds of modes such as bound, semi-bound, and radiation modes. Therefore, to model these SAW propagation effects, we subdivide the SAW structures in transverse direction into several parallel waveguiding channels (N regions), and take, as the wave-describing quantity, a two-dimensional scalar potential function. By doing so, we obtain a complete set of orthonormal modes into which an arbitrary transverse excitation function can be expanded to study its propagation. The general mode spectrum includes a discrete spectrum of bound modes and continuous spectra of semi-bound and radiation modes. We calculate all types of modes by making use of the stack matrix technique. The present work, which arose from the requirement of creating an efficient mathematical tool for the simulation of TCRFs, provides the complete analysis of general SAW multi-channel structures.     

Visualizing chemical compositions and kinetics of sol-gel by near-infrared multispectral imaging technique

Kinetics of sol-gel formation were studied using the recently developed near-infrared (NIR) multispectral imaging instrument. This imaging spectrometer possesses all the advantages of conventional spectrometers. It also has additional features that NIR spectrometers cannot offer, namely, its ability to provide kinetic information at different positions within a sample. The high spatial resolution and sensitivity of the InSb camera make it possible for the imaging spectrometer to determine the kinetic from data recorded by a single pixel. Kinetics of sol-gel reactions, determined by this multispectral imaging instrument, show that the initial hydrolysis of the TEOS, MTES, or a mixture of these two alkoxysilanes is relatively inhomogeneous. The inhomogeneity is dependent on the number of pixels used to calculate the spectrum for each spot. Data calculated from a single pixel provide the largest inhomogeneity. No inhomogeneity was observed when an average of a large number of pixels (e.g., 10 x 10) is used for calculation. The inhomogeneities observed for TEOS sol-gels are different from those for the MTES sol-gels, and those for sol-gels prepared from a mixture of TEOS and MTES are relatively larger and more similar to those of the MTES sol-gels. A variety of reasons might account for the observed inhomogeneities including differences in the structure of the TEOS sol-gels and MTES sol-gels and the inability of the TEOS to mix well with MTES with the latter being more hydrophobic.     

Low-intensity optical bistability in an active Fabry-Perot mirror induced by input-phase-insensitive parametric downconversion

A Fabry-Perot resonator filled with second-order nonlinear optical material is investigated. Attention is devoted to making the resonator act as a nonlinear mirror for ultralow-intensity light signals that can be switched by a control beam at the second-harmonic frequency. The interaction process is an input-phase-independent parametric downconversion. The theoretical problem is solved through implementation of a dummy variable method optimized for a parametric process. Efficient amplification and bistability of low-intensity signals have been found.