Mill tailings based composites as paste backfill in mines of U-bearing dolomitic limestone ore

This paper elaborates on the development of paste backfill using mill tailings generated during the processing of a uranium ore deposit hosted in dolomitic limestone. The tailings have been characterized in terms of the physical, chemical and mineralogical properties. Time-dependent rheological behaviors and geotechnical properties of cemented paste backfill (CPB) are also determined. The studies show that the mill tailing has the potential to form paste and the CPB has adequate strength to provide support to mine pillars, roofs, and walls.     

Chemical pretreatments and partial dehydration of ash gourd (Benincasa hispida) pieces for preservation of its quality attributes

Ash gourd (Benincasa hispida) is a commonly consumed vegetable in Asian subcontinent. Cut ash gourd pieces undergo severe decay within two days probably due to physical, biochemical and microbiological activities. Ash gourd pieces were chemically pretreated with sodium salt of ethylene diamine tetra acetic acid (sodium EDTA), calcium chloride (CaCl₂), citric acid and potassium metabisulphite (KMS) and dehydrated up to 30 percent moisture with an aim to extend its shelf life. Storage study of these samples was done with respect to texture, colour, bacterial content and water holding capacity. Shelf life was extended from two days to one month. Pretreatment using a combination of 1 mM EDTA, 2.5 percent KMS, 0.5 percent citric acid and 2.5 percent CaCl₂ and partial dehydration to 30 percent moisture found to be a good method in preservation of cut ash gourd pieces.     

On asymptotically efficient solutions for a class of supervisorycontrol problems

We consider restricted sequences of forbidden-string and forbidden-state problems and show the limiting problem instance defined by a sequence has a solution if and only if each problem instance in the sequence has a solution. Furthermore, the supervisor that enforces the desired behavior in the limiting problem instance also enforces the desired behavior in each problem instance in the sequence. In essence, the storage requirement for supervisory control of each instance is bounded above by that of the limiting problem instance. In addition, if the limiting problem instance is available, a similar observation can be made regarding the complexity of supervisory control. This observation coupled with recent results on the solvability of the supervisory control problem involving certain classes of nonregular behaviors and finite-representations of infinite-state systems is suggested as an effective procedure to combat the computational and storage issues in supervisory control. We conclude with an incomplete list of future research directions     

Estimating Fatigue Life of Bridge Components Using Measured Strains

The design fatigue life of a bridge component is based on the stress spectrum the component experiences and the fatigue durability. Changes in traffic patterns, volume, and any degradation of structural components can influence the fatigue life of the bridge. A fatigue life evaluation reflecting the actual conditions has value to bridge owners. Procedures are outlined in the AASHTO Guide Specifications for Fatigue Evaluation of Existing Steel Bridges to estimate the remaining fatigue life of bridges using the measured strain data under actual vehicular traffic. This paper presents the methodology with an actual case study of Patroon Island Bridge. The Patroon Island Bridge consists of ten spans. Spans 3 through 9 are considered the main spans and consist of steel trusses and concrete decks. Spans 1, 2, and 10 are considered approach spans and consist of plate girders. The overall bridge length is 1,795 feet. Strain data from critical structural members were used to estimate the remaining fatigue life of selected bridge components. The results indicate that most of the identified critical details have an infinite remaining safe fatigue life and others have a substantial fatigue life. Cracked floor beams were not addressed in this analysis, but have been recommended for retrofitting or replacement.     

On computing the supremal right-closed control invariant subset of a right-closed set of markings for an arbitrary petri net

A set of non-negative integral vectors is said to be right-closed if the presence of a vector in the set implies all term-wise larger vectors also belong to the set. A set of markings is control invariant with respect to a Petri Net (PN) structure if the firing of any uncontrollable transition at any marking in this set results in a new marking that is also in the set. Every right-closed set of markings has a unique supremal control invariant subset, which is the largest subset that is control invariant with respect to the PN structure. This subset is not necessarily right-closed. In this paper, we present an algorithm that computes the supremal right-closed control invariant subset of a right-closed of markings with respect to an arbitrary PN structure. This set plays a critical role in the synthesis of Liveness Enforcing Supervisory Policies (LESPs) for a class of PN structures, and consequently, the proposed algorithm plays a key role in the synthesis of LESPs for this class of PN structures.

     

Study of Structural and Electrical Properties of Conventional Furnace and Microwave-Sintered BaZr0.10Ti0.90O3 Ceramics

Structural, dielectric, piezoelectric, and ferroelectric properties of Zirconium-doped barium titanate (BaZr_0.10Ti_0.90O₃) ceramics prepared by microwave (MWS) and conventional (CS) sintering process are compared. X-ray diffraction and Raman spectroscopy indicate clearly the structural changes and confirm the effective diffusion of zirconium with the MWS technique to form BZT. Scanning electron microscopy reveals a fine grain, and a dense microstructure in the MWS ceramics processed under 4 h of cycle time (including heating, cooling, and holding time) in comparison with CS requiring 22 h. At room temperature the microwave sintered samples exhibit improved electrical properties exhibiting higher resistivity, higher dielectric constant, a lower dielectric loss, and a reduced dependence on frequency. Impedance and electric modulus spectroscopy analysis in the frequency range (40 Hz–1 MHz) and high-temperature range (573–873 K) suggests two relaxation processes attributed to bulk and grain boundary effects in the impedance plots for the both MWS and CS ceramics. The microwave-sintered BZT ceramics are found to be more attractive for room temperature device applications with improved properties, however, at higher temperatures they tend to degrade in comparison with the CS ceramics.     

Studies on optimization of parameters for dewatering of ground calcite-rich ore

This paper deals with filtration of very-fine size ground brecciated calcitic limestone ore slurry using flocculant chemicals. Screening of flocculants was carried out using capillary suction time (CST). Optimization of the neutral slurry filtration behaviour was carried out using a commercial non-ionic type polyacrylamide based synthetic flocculant. Response surface methodology and central composite rotatable design was used for model development and optimization of the filtration process. Critical filtration parameters such as applied vacuum, cake thickness and flocculant dosage were optimized. A correlation coefficient of 0.97 was obtained both for filtration rate and percent cake moisture. The analysis of variance of the determined model indicated that linear effects, interaction effects, quadratic effects, linear terms of all the three variables and some interaction among them are more significant for the filtration rate and cake moisture percent. The optimum filtration rate of 742 kg/(h m²) was obtained at the optimum conditions with cake moisture of 22.3%.     

Mapping and monitoring of degraded lands in part of Jaunpur district of Uttar Pradesh using temporal spaceborne multispectral data

Apart from soil erosion by wind and water, the major land degradation processes operating in irrigated commands in arid and semi-arid regions are waterlogging and subsequent salinization/alkalinization. Remote sensing data have been used successfully in studies of the spatial extent, magnitude and temporal behaviour of lands affected by such processes. In this work we interpreted Landsat Multispectral Scanner images acquired during 1975 and Landsat Thematic Mapper data acquired during 1993, in conjunction with ancillary information and adequate ground data, to derive information on the extent and spatial distribution of various degraded lands, namely salt-affected soils, waterlogged areas and eroded lands in part of the Jaunpur district of Uttar Pradesh. The results indicate a significant shrinkage in the spatial extent of salt-affected soils (of the order of 49.76%) over the period 1975 to 1993. A similar trend was observed in the temporal behaviour of waterlogged areas, but an increase (6.45%) was found in the spatial extent of eroded lands. The methodology employed and the observations made are described here in detail.     

Image transforms as a tool for the study of soil salinity and alkalinity dynamics

Principal components analysis (PCA), ratioing, image differencing and intensity-hue-saturation (IHS) transformation have been widely used in monitoring various natural resources and environmental hazards. In our study, the temporal behaviour of salt-affected soils in the Indo-Gangetic alluvial plains of Uttar Pradesh has been studied using Landsat MSS data for 1975 and 1992. Apart from routine digital classification of temporal MSS data using Guassian maximum likelihood algorithm, PCA, image differencing, and ratioing were also evaluated for their potential in bringing out temporal changes in salt-affected soils, if any. The results indicate that the third principle component, image differencing, and ratioing of the first two MSS bands for two periods have brought out substantial information associated with the temporal behaviour of saltaffected soils.     

Process parametric study for the recovery of very-fine size uranium values on super-conducting high gradient magnetic separator

This paper discusses the application of super-conducting high gradient magnetic separator for the recovery of very-fine size uranium bearing mineral values present in the flotation tailings of an Indian copper ore. The U₃O₈ content of the tailings is 0.009%. The focus of this study is centered on determining the effect of various process variables like applied magnetic field, wool filling factor in the canister, wool diameter, loading capacity of the matrix, feed flow-rate and slurry pH on the recovery of uranium values in the magnetized matrix. The results indicate significant improvement in the recovery of <10 μm size uranium bearing particles, to the extent of 60–65% in SCHGMS as against mere 20% in other high intensity magnetic separators. The enrichment ratio of U₃O₈ values in the magnetic fraction was in the range of 2.2–2.5 only due to interference from other magnetic minerals.