Effectiveness of 3D Geoelectrical Resistivity Imaging using Parallel 2D Profiles

Acquisition geometry for 3D geoelectrical resistivity imaging in which apparent resistivity data of a set of parallel 2D profiles are collated to 3D dataset was evaluated. A set of parallel 2D apparent resistivity data was generated over two model structures. The models, horst and trough, simulate the geological environment of a weathered profile and refuse dump site in a crystalline basement complex respectively. The apparent resistivity data were generated for Wenner–alpha, Wenner–beta, Wenner–Schlumberger, dipole–dipole, pole–dipole and pole–pole arrays with minimum electrode separation, a (a = 2, 4, 5 and 10 m) and inter-line spacing, L (L = a, 2a, 2.5a, 4a, 5a and 10a). The 2D apparent resistivity data for each of the arrays were collated to 3D dataset and inverted using a full 3D inversion code. The 3D imaging capability and resolution of the arrays for the set of parallel 2D profiles are presented. Grid orientation effects are observed in the inversion images produced. Inter-line spacing of not greater than four times the minimum electrode separation gives reasonable inverse models. The resolution of the inverse models can be greatly improved if the 3D dataset is built by collating sets of orthogonal 2D profile

Field Evaluation of 3D Geo-electrical Resistivity Imaging for Environmental and Engineering Studies Using Parallel 2D Profiles

Eight parallel two-dimensional (2D) geo-electrical resistivity profiles were generated in hard-rock (Pulivendla) area of Andhra Pradesh, India using a Lund imaging multi-electrode system adopting Wen-ner array. The aim of the survey was to experiment-tally evaluate the effectiveness of using parallel 2D profiles for three-dimensional (3D) geo-electrical resistivity imaging for better understanding of aquifer geometry and its characteristics. The observed 2D apparent resistivity data were independently inverted, and then collated to 3D data set. The inversion of the resulting 3D data set was carried out using a full 3D inversion code. The 3D inverse model of resistivity images obtained are presented as horizontal depth slices. The 2D images extracted from 3D inverse models showed no distortions that are observed in 2D models obtained by 2D inversion. The 3D inverse model resis-tivity appears to be more realistic, considering the hydrogeology of the area. The unusually high resistiv-ity values observed in the 2D inverse models were not observed in the 3D inverse models. The very low near-surface inverse model resistivity observed is thought to be structurally influenced. The results, which are consistent with numerical evaluation, show that high resolution 3D geoelectrical resistivity imaging can be successfully conducted using parallel 2D profiles if appropriate survey parameters are carefully chosen

Occurrence of elevated nitrate in groundwaters of Krishna delta, India

Nitrate concentrations were measured in the groundwater samples of Krishna delta, India. The results indicate a large variation of nitrate from 10 - 135 mg/l. In 79 groundwater samples, about 39% shows high nitrate contents (>50 mg/l), which is more than the permissible limits in drinking water. In north Krishna delta 49% and in south Krishna delta 26% water samples were found to exceed the permissible limits. This study indicates that groundwater of north Krishna delta is more polluted than south. Nitrate pollution level is found more in dug wells compared to hand pumps/bore wells. In this region 49% dug wells and 31% hand pumps have exceeded the desirable limits. The possible sources for the high nitrate level in groundwater were identified as excessive utilization of nitrogenous fertilizers for agricultural purposes.Key words: Nitrate pollution, groundwater, Krishna delta, India

Numerical Evaluation of 3D Geoelectrical Resistivity Imaging for Environmental and Engineering Investigations Using Orthogonal 2D Profiles

Field design for 3D data acquisition in geoelectrical resistivity imaging using a net of orthogonal sets of 2D profiles was numerically investigated. A series of 2D apparent resistivity pseudosections were generated over a synthetic horst structure representing the geological environment of a crystalline basement in low latitude areas using RES2DMOD code. Different minimum electrode separations and inter-line spacing were used with a view of determining the optimum inter-line spacing relative to the minimum electrode separation. The 2D apparent resistivity data were collated to 3D data set and then inverted using RES3DINV, a full 3D inversion code. The relative effectiveness and imaging capabilities of Wenner-alpha (WA), Wenner-beta (WB), Wenner-Schlumberger (WSC), dipole-dipole (DDP), pole-dipole (PDP), and pole-pole (PP) arrays to image the structure using a net of orthogonal set of 2D profiles are presented. The normalized average sensitivity of the inversion results show that WSC, DDP, and PDP arrays are more sensitive to the 3D structure investigated. Interline spacing of not greater than four times the minimum electrode separation gives reasonable resolution

Application of 2D and 3D Geoelectrical Resistivity Imaging for Engineering Site Investigation in a Crystalline Basement Terrain, Southwestern Nigeria

Orthogonal set of 2D geoelectrical resistivity field data, consisting of six parallel and five perpendicular profiles, were collected in an investigation site using the conventional Wenner array. Seven Schlumberger soundings were also conducted on the site to provide ID layering information and supplement the orthogonal 2D profiles. The observed 2D apparent resistivity data were first processed individually and then collated into 3D data set which was processed using a 3D inversion code. The 3D model resistivity images obtained from the inversion are presented as horizontal depth slices. Some distortions observed in the 2D images from the inversion of the 2D profiles are not observed in the 2D images extracted from the 3D inversion. The survey was conducted with the aim of investigating the degree of weathering and fracturing in the weathered profile, and thereby ascertaining the suitability of the site for engineering constructions as well as determining its groundwater potential

Effect of planting techniques and weed control treatments on growth and yield of wheat

A field experiment was conducted to study the effect of different planting techniques (conventional drill sowing at 16, 18 and 20 cm row spacing and bed planting with two and three rows in main plots) and weed control treatments (pinoxaden 50 g/ha, ready-mix (RM) of carfentrazone and metsulfuron 25 g/ha and pinoxaden 50 g/ha + RM of carfentrazone and metsulfuron 25 g/ha in subplots) on growth and productivity of wheat. The grain yield under row spacing 18 cm (53.30 q/ha), and 20 cm (52.02 q/ha), and three rows bed planting (51.96 q/ha) were recorded statistically at par with each other and significantly higher than 16 cm (49.37 q/ha) row spacing and two row bed planting (48.53 q/ha). Gross returns (Rs. 95637/ha) and net returns (Rs. 43929/ha) and B:C ratio (1.85) were record-ed higher under 18 cm row spacing compared to other planting techniques. Tank mixed application of pinoxaden 50 g/ha + RM of carfentrazone and metsulfuron 25 g/ha applied at 35 days after sowing (DAS) controlled both grassy and broad leaved weeds effectively with lower values of weed dry matter accumulation (7.67 g/ha) and produced growth parameters, yield attributes and yield (53.16 q/ha) at par with weed free treatment. In light of the results to maximise productivity, 18 cm row spacing may be practiced and tank mix application of pinoxaden (50 g/ha) + RM of carfentrazone and metsulfuron (25 g/ha) is recommended to reduce losses due to complex weed flora in wheat

Dynamics of a camphoric acid boat at the air–water interface

We report experiments on an agarose gel tablet loaded with camphoric acid (c-boat) spontaneously set into motion by surface tension gradients on the water surface. We observe three distinct modes of c-boat motion: harmonic mode where the c-boat speed oscillates sinusoidally in time, a steady mode where the c-boat maintains constant speed, and an intermittent mode where the c-boat maintains near-zero speed between sudden jumps in speed. Whereas all three modes have been separately reported before in different systems, controlled release of Camphoric Acid (CA) from the agarose gel matrix allowed the observation of all the three modes in the same system. These three modes are a result of a competition between the driving (surface tension gradients) and drag forces acting on the c-boat. Moreover we suggest that there exist two time scales corresponding to spreading of CA and boat motion and the mismatch of these two time scales give rise to the three modes in boat motion. We reproduced all the modes of motion by varying the air–water interfacial tension using Sodium Dodecyl Sulfate (SDS)

Effect of different dates of sowing on yield attributes, yield and quality of Barley (Hordeum vulgare L.) cultivars

A study was conducted during rabi2013-14 at Barley Research Area of CCS Haryana Agricultural University, Hisar with the objective to study the effect of different date of sowing on growth, yield and quality characters of barley cultivars. The experiment was laid out in a split plot design with five date of sowing (30th October, 10th, 20th, 30th November and 10th December) in main plots and four cultivars (BH 902, RD 2552, DWRUB 52 and RD 2668) kept in sub plots replicated thrice. Crop sown on 30th October produced significantly higher values of growth parameters, yield attributes (115 productive tillers per meter row length, no. of grains per spike- 37 and test weight -46.90) and yield (grain yield- 4733 kg ha-1 and straw yield- 8368 kg ha-1). But it was statistically at par with 10th November sowing date. Grain protein content, hectoliter weight and bold grains percentage decreased significantly with delay in sowing while malt content percentage was recorded significantly higher (89.53%) in 10th December date of sowing. Among the cultivars DWRUB 52 produced significantly higher grain yield (4516 kg ha-1) and quality attributes like malt content (86.25%) than other cultivars

Experimental Evaluation of 3D Geoelectrical Resistivity Imaging using Orthogonal 2D Profiles

Numerical evaluation of 3D geoelectrical resistivity imaging was conducted using orthogonal set of 2D pseudo-sections generated over two synthetic models, horst and trough models. The models represent geological environment that simulates a typical weathered profile and refuse dump site in a crystalline basement complex, respectively. Different arrays including Wenner-alpha (WA), Wenner-beta (WB), Wenner-Schlumberger (WSC), dipole-dipole (DDP), pole-dipole (PDP), and pole-pole (PP) arrays were used for the data generation. The 2D apparent resistivity data were collated to 3D data set and then inverted using a full 3D inversion code. The effectiveness of the technique for 3D resistivity imaging as well as the imaging capabilities of the selected arrays is evaluated. The observed anomaly effect and normalized model sensitivities of the arrays indicate that DDP and PDP arrays are more sensitive to the 3D features, while WSC show moderate sensitivity to 3D features. Field example in which the technique was applied in a 3D geoelectrical resistivity imaging for engineering site investigation in the crystalline basement complex of southwestern Nigeria is also presented

Prediction of Storage Life of Propellants having Different Burning Rates using Dynamic Mechanical Analysis

Propellants, visco-elastic in nature, show time and temperature dependent behaviour on deformation. Hence, the time–temperature superposition principle may be applied to the visco-elastic properties of propellants. In the present study, dynamic mechanical analyser (DMA) was used to evaluate the dynamic mechanical properties and quantify the storage life of four different propellants based on hydroxyl terminated polybutadiene, aluminium and ammonium perchlorate having different burning rates ranging from 5 mm/s to 25 mm/s. Each sample was given a multi-frequency strain of 0.01 per cent at three discrete frequencies (3.5 Hz, 11 Hz, 35 Hz) in the temperature range - 80 °C to + 80 °C. The storage modulus, loss modulus, tan delta and glass transition temperature (Tg) for each propellant samples have been evaluated and it is observed that all the propellants have shown time (frequency) and temperature dependent behaviour on deformation. A comparison of the log aT versus temperature curves (where aT is horizontal (or time) shift factor) for all four propellants indicate conformance to the Williams–Landel–Ferry (WLF) equation. The master curves of storage modulus (log É versus log ω plots) were generated for each propellant. A plot of É versus time for all propellants was generated up to 3 years, 6 years, and 10 years of time, respectively. The drop in the storage modulus below the acceptable limit with time may be used to predict the shelf life of the propellant.Defence Science Journal, 2012, 62(5), pp.290-294, DOI:http://dx.doi.org/10.14429/dsj.62.248