A generalized methodology for determination of crushing strength of granular materials

Determination of crushing strength of granular material is very important for assessing its suitability in various engineering and industrial applications. Laboratory investigations that would yield stress–strain behaviour, and hence, crushing strength of the granular material are extremely cumbersome and time consuming. Also, results obtained from these experiments get influenced by the aspect ratio of the sample, its density, strain rate, size and shape of the grains etc. These difficulties can be overcome by developing a generalized mathematical model, which is primarily based on the physical properties of the granular material such as particle-size and specific gravity, for estimating its crushing strength. With this in view, experiments were conducted on different types of granular materials such as sands, cenospheres (which are found in fly ash and bottom ash) and glass beads, and the results were used for developing such a model. Details of the testing methodology adopted to achieve this are also presented in this paper and validation of the proposed model has been done based on the experimental results and the results reported in the literature.     

Recent Trends of Arctic and Antarctic Summer Sea-Ice Cover Observed from Space-Borne Scatterometer

Long term variations in Sea ice distribution strongly influence the atmosphere and ocean in the polar regions. In the recent period significant variations in sea ice cover have been observed in both the hemispheres. In the past, studies have been carried out that report the trends either at the Arctic/Antarctic level or at sector level. However, only a few studies have concentrated on the investigation of trends at grid level using scatterometer data. The present study focuses on the investigations of the sea ice trend at 1 × 1 degree grid level over the period 2000–2007 using QuickSCAT 0.2-degree resolution Scatterometer data. It was observed that in the Arctic overall monthly trend is negative in all the sectors, with the Arctic level decline of 3.26% per year. In the Antarctic, region-wise different trends have been observed. Negative trend is observed in the Amundsen- Bellingshausen Seas and also in the Indian Ocean sector near the continental Ice shelves. It was highlighted that significant trends exists within the pockets of marginal seas.     

Study of indices for drought characterization in KBK districts in Orissa (India)

Drought is a temporary, random and regional climatic phenomenon, originating due to lack of precipitation leading to water deficit and causing economic loss. Success in drought alleviation depends on how well droughts are defined and their severity quantified. A quantitative definition identifies the beginning, end, spatial extent and the severity of drought. Among the available indices, no single index is capable of fully describing all the physical characteristics of drought. Therefore, in most cases it is useful and necessary to consider several indices, examine their sensitivity and accuracy, and investigate for correlation among them. In this study, the geographical information system‐based Spatial and Time Series Information Modeling (SPATSIM) and Daily Water Resources Assessment Modeling (DWRAM) software were used for drought analysis on monthly and daily bases respectively and its spatial distribution in both dry and wet years. SPATSIM utilizes standardized precipitation index (SPI), effective drought index (EDI), deciles index and departure from long‐term mean and median; and DWRAM employs only EDI. The analysis of data from the Kalahandi and Nuapada districts of Orissa (India) revealed that (a) droughts in this region occurred with a frequency of once in every 3 to 4 years, (b) droughts occurred in the year when the ratio of annual rainfall to potential evapotranspiration (Pae/PET) was less than 0·6, (c) EDI better represented the droughts in the area than any other index; (d) all SPI, EDI and annual deviation from the mean showed a similar trend of drought severity. The comparison of all indices and results of analysis led to several useful and pragmatic inferences in understanding the drought attributes of the study area. Copyright © 2007 John Wiley & Sons, Ltd.     

Haser model CN,C2 and C3 production rates in some comets

Emission fluxes of CN, C₂ and C₃ species observed in the coma of some comets are analysed in the framework of Haser model. CN, C₂ and C₃ production rates are determined using recently derived fluorescence efficiencies and dependence of CN, C₂ and C₃ production rates on the heliocentric distance is studied. Evidence for a burst type activity around January 15, 1974 in the post-perihelion period of comet Kohoutek (1973f) is observed.     

An analysis of spectrophotometric observations of comets Austin (1982g) and Bradfield (1980t)

Post-perihelion observed emission fluxes at 388 nm (CN) and 516 nm (C₂) of the coma of comets Austin (1982g) and Bradfield (1980t) are analysed in the framework of the Haser model. Ratios of Haser model CN and C₂ parent production rates with expansion velocity show that each comet behaves normally. For comet Austin (1982g), the Q _CN/v and Q _c2/v values decrease with increase of heliocentric distance of comet. For an assumed %; activity of the total spherical surface area of the nucleus, the water vaporization theory coupled with derived water production rates from the International Ultraviolet Explorer H and OH flux data yields a nuclear diameter of about 6 km for comet Austin (1982g). For comet Bradfield (1980t), the derived nuclear diameter is expected to be of about 1 km. In each comet, the dust mass production rates as well as ratio of dust-to-gas mass production rates decrease with increase of heliocentric distance of comet.     

Thermal-convective instability of a rotating plasma in stellar atmospheres with Hall effect

Thermal-convective instability of a hydromagnetic, composite, rotating, inviscid, and infinitely conducting plasma in a stellar atmosphere has been studied in the presence of Hall currents. It is found that the criterion for monotonic instability holds good in the presence of the effects due to rotation and Hall currents.     

A note on some static scalar-gravitational fields

In this note extending the technique developed for static fields by De (1964) to the static plane-symmetric solution of Taub (1951) and the conformastat gravitational universe of Das (1971) solutions for coupled gravitational and zero-rest-mass scalar fields have been obtained. Furthermore, it is found that the singularities of these empty spaces cannot be removed by the introduction of zero-rest-mass scalar fields.     

A non‐equilibrium sediment transport model for rill erosion

Sediment transport in rill flows exhibits the characteristics of non‐equilibrium transport, and the sediment transport rate of rill flow gradually recovers along the flow direction by erosion. By employing the concept of partial equilibrium sediment transport from open channel hydraulics, a dynamic model of rill erosion on hillslopes was developed. In the model, a parameter, called the restoration coefficient of sediment transport capacity, was used to express the recovery process of sediment transport rate, which was analysed by dimensional analysis and determined from laboratory experimental data. The values of soil loss simulated by the model were in agreement with observed values. The model results showed that the length and gradient of the hillslope and rainfall intensity had different influences on rill erosion. Copyright © 2006 John Wiley & Sons, Ltd.     

Some Exact Solutions of String Cosmological Models in Bianchi Type-V Space-Time

The Bianchi type-V cosmological solutions of massive strings in the presence and absence of the magnetic field are investigated. The physical behavior of these models are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Soret effects on free-convection and mass transfer flow in the stokes problem for a infinite vertical plate

An analytical study is performed to examine the free-convection and mass transfer flow for the Sokes problem for an infinite vertical plate on taking into account the Soret effect (thermal diffusion effect). The Laplace transform technique is used to obtain the expressions for velocity and skin-friction. The effect of Soret numberS on velocity field and skin-friction is extensively discussed with the help of graphs and table.