Mudbank regime off the Kerala coast during monsoon and non-monsoon seasons

Field experiments conducted in the nearshore ocean to understand the dynamics of mudbank off Kerala, south-west coast of India, are highlighted. Real time monitoring of the nearshore ocean off Purakkad, Kerala was accomplished using pressure transducers for nearshore surface wave measurements, and current sensors for nearshore velocity measurements. Comprehensive information on the spatial structure of mudbank was obtained from aerial surveys. Extensive data collected on surface waves and currents in the nearshore ocean, indicate that the infra-gravity (IG) waves (leaky modes and trapped edge wave modes), and far infra-gravity (FIG) waves coupled with strong shoreline reflections and undertow play an important role in the dynamics associated with the mudbanks off Kerala during the monsoon season. During the non-monsoon season evidence for progressive edge waves in the infragravity frequency band, an energetic gravity wave band and a strong undertow with weak reflections was observed.     

Dependence on pressure of conduction by hopping of small polarons in minerals of the Earth's lower mantle

Electrical conductivity of the lower mantle-like assemblage (Mg,Fe)SiO₃ perovskite-(Mg,Fe)O magnesiowüstite is usually analyzed using the quasi-chemical Arrhenian approach of diffusion. The conductivity of this assemblage has often been attributed to hopping of small polarons, because of the low value of the activation energy and the small negative activation volume. However, the solid-state physics approach can provide more arguments, for or against conduction by polarons. We have tried to bridge the gap between the two approaches and identify the physical quantities entering the phenomenological activation parameters. In particular, we have investigated the pressure dependence of the activation energy, and the physical meaning of the activation volume. Hopping is controlled by the binding energy of the polaron and by the value of the exchange integral, which increases with pressure causing the observed decrease of the activation energy. From the physical theory and the results of experiments at pressures up to 40 GPa and temperatures up to 400 ^∘C, we have estimated the values of parameters characteristic of polarons: radius, mobility, time between jumps and adiabaticity. These values are compatible with conduction by small adiabatic polarons. The consequences for extrapolations to lower mantle conditions of the presence of a temperature dependent preexponential term in the expression for conductivity have been examined. It was found that the extrapolations are not significantly different from those using the Arrhenius equation. Received: 5 November 1998 / Revised, accepted: 4 May 1999     

Schotcrete as permanent lining for the Furka base tunnel

Summary The lining concept of the 15.4 km long one-track Furka railway tunnel is described with particular emphasis on shotcrete application as a permanent support Altogether 70000 m³ dry aggregate/ cement mix and 115000 rock bolts have been applied. The tunnel was lined at a rate of approx. 400 tunnel metres per month using up to five shotcrete machines simultaneously. Systematic quality control throughout the construction work indicated an average uniaxial compressive strength of shotcrete of 40 N/mm². The support requirements were grouped into 16 different classes and an additional special class accounting for extreme geological conditions in some relatively short stretches.     

Spatial distribution of uranium and vanadium in the upper phosphorite member in Eshidiyya basin, southern Jordan

Geostatistical analysis of geochemical exploration data can provide useful information for evaluating the mineralization potential of geologic bodies. The main objective of this study was to evaluate the spatial distribution of U and V over an area in the upper phosphorite member, the A0 unit, in Eshidiyya basin in southern Jordan. Drill-hole samples were analyzed. The geochemistry of the analyzed elements was assessed. The spatial variability of U and V was also assessed using semivariance analysis. Both U and V were found to exhibit a normal distribution as indicated by the constructed histograms and the calculated skewness and kurtosis coefficients. Exponential models with nugget effects were fitted to the experimental semivariograms. Ordinary kriging was performed to generate geochemical maps. The applied interpolation technique proved to be the best in producing geochemical exploration maps for both U and V in Eshidiyya phosphorites. The constructed geochemical maps helped visualize a WNW–ESE U mineralization trend in the studied phosphorites. This trend should be taken into consideration in any future exploration programs for U in south Jordan.     

Application of a square wave potentiometry technique for electroreductive sulfur removal from a thiophenic model fuel

Thiophene-containing solutions were electroreductively desulfurized by a dynamic method. Initially, cyclic voltammetry was utilized to study thiophene electroadsorption from aqueous solution onto a platinum electrode surface and also to investigate the thiophene electroreductive behavior. Then, the solution was desulfurized via a square wave potentiometry method. The objective of this study was to find the optimal conditions. In this regard, the best adsorption potential, electroreduction potential, and square wave frequency were found to be ?0.54 V, ?0.95 V, and 1 Hz, respectively. Finally, a model fuel (containing 294 part per millions thiophene) was desulfurized by the square wave potentiometry method. Gas chromatography and Fourier transform infrared spectroscopy were used to examine the feed and product solutions. Gas chromatographic measurements revealed that sulfur content decreased to 55 part per millions. Based on the acquired results, electroreductive desulfurization could be designated as an efficient superseded for the commercial hydrodesulfurization process. However, more studies must perform to overcome technical limitations of electroreductive desulfurization technique and to guarantee its reliability.     

An integration-based estimation approach for the determination of slug test parameters under various flow geometries

A simple parameter estimation procedure, designated as integration-based estimation (IBE), was introduced to determine the hydraulic properties of an aquifer using slug test models subjected to certain flow geometries such as radial and spherical flows. The basic idea behind the proposed IBE approach is to link an integration value at pre-defined normalized head levels for field data with that of a theoretical type curve. The IBE method removes the need for the implementation of the classical graphical matching process which would be ineffective to acquire aquifer parameters for non-ideal aquifer conditions. As the second aspect of this study, a new decision tool was suggested to determine the suitable slug test model to be utilized for the site data since diagnosing the flow character properly is of crucial importance for following a convenient analysis procedure. The estimation performance and limitation of the proposed IBE method were tested for several slug test scenarios including radial and spherical flow models with a number of synthetically generated data sets as well as a field application. Results reveal that the IBE together with the identification methodology not only is able to retrieve aquifer parameters as reliable as the existing techniques in the literature but also diagnoses the flow character precisely as demonstrated in this study.