Calibration of a constitutive model using genetic algorithms

Before any constitutive model can be used in a numerical procedure, the model needs to be calibrated using laboratory test results. The traditional calibration techniques use stress and strain levels at certain states that a material undergoes during certain types of laboratory tests. Sometimes this method of calibrating a constitutive model fails to capture the overall behavior of a material, i.e. behavior at every point in stress/strain path. In this paper, we have shown how a random search technique, genetic algorithm (GA), can be used to calibrate constitutive models. The advantages of using GA are that it considers the overall behavior of a material, not the behavior at some specific states as the traditional method does, and it can work with many types of laboratory tests. The concept is applied to calibrate the hierarchical single surface (HiSS) δ_l model for geologic materials. Three cases have been studied where the difference is in the type of test data used to calibrate the model. These three different test data are: (1) simulated conventional test data, (2) simulated cyclic test data, and (3) real test data. A comparison of two different cross-over schemes, one-point and six-point, has been made.     

Interactive effect of cadmium and zinc on chromium uptake in spinach grown in Vertisol of Central India

A pot culture experiment was conducted to study impact and interaction of multi-metals on growth, yield and metals uptake by spinach (variety All Green). Three levels of each chromium (0, 50 and 100 mg/kg), cadmium (0, 1 and 2 mg/kg) and zinc (0, 10 and 20 mg/kg) in combinations (total treatments 3 × 3 × 3 = 27) were applied in a Vertisol (5 kg). The results showed that increasing the concentration of chromium, cadmium and zinc in soil enhanced the respective metal concentrations in spinach root and shoot. When cadmium at 2 mg/kg along with chromium at 100 mg/kg soil was applied, chromium concentration and uptake were decreased in root and shoot. Meanwhile, zinc application had no significant effect on chromium uptake and concentration in spinach biomass. From the results, it was concluded that cadmium at higher dose had an antagonistic effect over chromium. On the other hand, in chromium, cadmium and zinc combinations particularly at their higher levels, a competition among each other was found. Therefore, the findings could be used as guidelines for controlling and management of heavy metals pollution in farmland.     

A comparative study of soil erosion modelling by MMF,USLE and RUSLE

The quantitative assessment of spatial soil erosion is valuable information to control the erosion. The study area in a part of Narmada river in central India is selected. The main objective is to assess and compare the results obtained from three soil erosion models using GIS platform. Variation in the rate of erosion of the three models is compared considering varying slope, soil and land use of the area. Three models selected are Morgan–Morgan–Finney (MMF), Universal Soil Loss Equation (USLE) and Revised Universal Soil Loss Equation (RUSLE). The best fit or the most reliable model for the study area is selected after validation with the observed sedimentation data. The results give –39.45%, –9.60% and 4.80% difference in the values of sedimentation by MMF, USLE and RUSLE, respectively, from the observed data. Finally, RUSLE model has been found to be most reliable for the study area.     

Impact of INSAT-3D radiance data assimilation using WRF 3DVAR on simulation of Indian summer monsoon and high-resolution rainfall forecast over hilly terrain

Natural Hazards - This study describes the impact of assimilation of INSAT-3D radiances data from both imager and sounder for Indian summer monsoon simulation and rainfall forecast over a hilly...     

Mercuric Chloride Induced Inhibition of Acid and Alkaline Phosphatase Activity in the Kidney of Mudskipper,Boleophthalmus dentatus

The present paper deals with the inhibition of the specific activity of the acid and alkaline phosphatases in the kidney tissue of mudskipper Boleophthalmus dentatus, exposed to different sublethal concentrations of mercuric chloride. There was a more or less linear inhibition of the specific activity of both the enzymes with increasing concentration of mercuric chloride as well as exposure time. The inhibition of acid phosphatase could be due to the rupture of lysosomal membrane in the presence of mercury compound, which acts as a labilizing agent. The inhibition of alkaline phosphatase probably caused a breakdown of the membrane transport system.     

Recent advances in solar radio physics

We review high spatial resolution microwave observations of solar active regions, coronal loops and flares. Observations of preflare active regions are presented; in particular we discuss the interpretations of reversal of polarization at the flare site and the role of newly emerging flux in triggering the onset of flares. We discuss the spatial locations of microwave burst emitting regions; loops or arcades of loops appear to be the sites of flare energy release in microwave bursts. We provide direct observational evidence of magnetic reconnection as the primary cause of acceleration of electrons in microwave bursts.     

Solar active regions at 9 and 3.5 mm wavelengths under disturbed conditions

Some properties of solar active regions at 9 and 3.5 mm wavelengths under disturbed conditions are discussed. New regions develop or weak regions intensify at millimeter wavelengths as a result of flares at distant sites. The spectra of the peak flux density of moderately strong bursts observed at 9 mm show a sharp drop toward the shorter millimeter wavelengths. The weak bursts at 3.5 mm manifest mainly as heating phenomena.     

Radio Detection of a Rapid Disturbance Launched by a Solar Flare

We report the direct observation of motion associated with a solar flare at a speed of 26,000 km s-1. The motion is seen from a radio source at 0.33 GHz, which suddenly starts moving during the flare. At its peak, the radio source covers a quiet region of dimension 500&arcsec;. Emission from any given location is sporadic. The disturbance itself does not seem to radiate, but it excites coronal features that continue to radiate after it passes. The inferred velocity is larger than any previously inferred velocity of a disturbance in the solar atmosphere apart from freely streaming beams of accelerated electrons. The observed motion of the source at a fixed frequency, low polarization, and moderate bandwidth are more consistent with the typical properties of moving type IV radio bursts than with classical coronal shock-associated type II bursts, but any disturbance at such a high velocity must be highly supersonic and should drive a shock. We speculate that the disturbance is associated with the realignment of magnetic fields connecting different portions of an active region.     

Optimization of Nowcast Software WDSS-II for operational application over the Indian region

Nowcasting in the India Meteorological Department (IMD) is being provided for T + 0 to T + 2 h, using the Warning Decision Support System (WDSS-II) software. Prior to operational nowcasting over the Indian region, the parameters of the nowcast algorithm tool of the software were optimized, and accuracy was evaluated for various weather systems over Delhi. This optimization is demonstrated in this study with reference to three weather systems over Delhi, with each case representing one of three typical types of cloud systems over the region. These are—(a) convective lines associated with winter and early pre-monsoon weather systems, (b) deep convective cells that form in the pre-monsoon (April–June) and post-monsoon season (October–November) and (c) wide convective echoes that form during the monsoon season. The efficacy of the algorithm was assessed on a frame-by-frame basis as well as holistically for entire convective episodes. The important findings of the frame-by-frame study are (1) the inability of the inbuilt growth-decay algorithm to capture the evolution of storm cells, (2) setting of the threshold of detection of storms and tracking storms and (3) number of scales through which storms should be tracked. The holistic capabilities of the nowcast algorithm were tested for entire convective episodes using Model Evaluation Tools software. The results indicate that the advection algorithm tends to move the convective areas faster than observed at all time scales. Hence the multi-scale segmentation approach (over the two-scale approach) increases the smoothening of the output, at the cost of decreased nowcast skill. The inter-event comparison indicates that the low-intensity convective line zones, which are characteristic of winter and early pre-monsoon weather systems, have the most rapid temporal change in the overall area under convection. This leads to larger area errors during nowcasting of these systems. On the other hand, pre-monsoon systems comprised mostly isolated cells that reach great heights and move very fast, but do not have much horizontal area growth. The error in the nowcasting of these systems is mostly in respect of location error, as well as error in forecast of the intensity of the cells. The overall error in nowcasting is least for the monsoon systems over the Delhi region.