Pattern of crack formation in rice grain as influenced by shape and orientation of cells

Stress cracks usually develop across the grain in rice, although longitudinal cracks also develop occasionally on one axis. On examination of sections of rice grain it was noticed that orientation of elongated cells provided cell wall continuation across the grain and also along the length in the dorsiventral axis. Cracks were found to develop easily along these cell wall lines. Crack formation was difficult in the lateral axis along the length since cell wall continuity was absent. However, when severely dried grains were suddenly wetted cracks developed even in this axis by disruption of cells along the cleavage path.     

An investigation into the stability of enclosed laminar diffusion flames

Experiments on enclosed laminar diffusion flames have revealed the existence of a critical relative velocity of air and fuel which is associated with the threshold of low frequency flame vibration. Starting from the hypothesis that these vibrations are triggered by a selectively amplified disturbance arising in the free shear layers near the base of the flame, the authors have obtained evidence of the nature of the disturbance. Further systematic experiments have enabled them to account for the observed behavior of low frequency vibrating diffusion flames in the light of their hypothesis and in relation to the acoustical properties of their combustion system.     

Two-phase flow regimes in round, square and rectangular tubes during condensation of refrigerant R134a

An experimental investigation of two-phase flow mechanisms during condensation of refrigerant R134a in six small diameter round (4.91 mm), square (D_h=4 mm, α=1), and rectangular (4×6 and 6×4 mm: D_h=4.8 mm, α=0.67 and 1.5; 2×4 and 4×2 mm: D_h=2.67 mm, α =0.5 and 2) was conducted. Unique experimental techniques and test sections were developed to enable the documentation of the flow mechanisms during phase change. For each tube under consideration, flow mechanisms were recorded over the entire range of qualities for five different refrigerant mass fluxes between 150 and 750 kg m⁻² s⁻¹. The flow mechanisms were categorized into four different flow regimes: intermittent flow, wavy flow, annular flow, and dispersed flow. In addition, the large amount of data enabled the delineation of several different flow patterns within each flow regime, which provides a clearer understanding of the different modes of two-phase flow. Transition lines between the respective flow patterns and regimes on these maps were established based on the experimental data. It was found that for similar hydraulic diameters, flow regime transitions are not very strongly dependent on tube shape or aspect ratio. These maps and the transition lines can be used to predict the particular flow pattern or regime that will be established for a given mass flux, quality and tube geometry.     

Synthesis of Cyclic Carbonates from Olefins and CO2 over Zeolite-Based Catalysts

Metal phthalocyanine complexes (MPc; M = Cu²⁺, Co²⁺, Ni²⁺ and Al³⁺) encapsulated in zeolite-Y exhibit high catalytic activity for the cycloaddition of CO₂ to epichlorohydrin and propylene oxide yielding the corresponding cyclic carbonates. The catalysts could be separated easily from the reaction mixture and reused with little loss in activity. These environmentally benign catalysts are also more efficient than either the neat complexes or those obtained by supporting them on solids like silica.     

Estimation of number-area-frequency dimensions of surface water bodies

This paper proposes a technique that includes a set of mathematical morphological transformations to estimate the frequency dimension. The dimension computed through a power law relationship is tallied with the dimension computed through a correlational plot. This technique is demonstrated on a two-dimensional section embodying a large number of surface water bodies, extracted from remotely sensed data, situated randomly, and the frequency dimension (D) for surface water bodies yields straight-line dependence of lnC(r) (correlational integral) on ln(r) (radius of structuring template). The correlational integral is computed for two aspects by considering the number of water bodies and their corresponding occupied areas. The number-frequency dimension and the area frequency dimension computed through correlational plots yield straight-line dependencies with slopes that are greater than unity but less than 2.0 (1.3 and 1.7, respectively).     

Seismic retrofitting of nonductile beam-column sub-assemblage using FRP wrapping and steel plate jacketing

The paper discusses the aspects of repair and retrofitting technique adopted for a damaged reinforced concrete beam-column joint specimen under cyclic loading. A specimen designed based on Indian Standard specifications with consideration of seismic load but without adopting ductile detailing (NonDuctile) was investigated under reverse cyclic loading. Then, the damaged nonductile specimen was repaired with epoxy mortar and grouted using low viscous polymer, and retrofitted using fiber reinforced plastic (FRP) wrapping in beam and column components and steel plate jacketing in joint region. The experimental results showed that the retrofitted specimen not only regained its original strength and stiffness but also has overcome the deficiencies of nonductile detailing. The present study shows that a proper repair and adequate retrofitting technique can be used for strengthening and improvement of damaged regions in reinforced concrete structures.     

Behaviour of organised disturbances in fully developed turbulent channel flow

In our earlier work we have shown the relevance of stability theory in understanding the sustenance of turbulence in turbulent boundary layers. Here we adopt the same model to study the evolution of organised disturbances in turbulent channel flow. Since the dominant modes are wall modes we find that the stability characteristics in the two flows are nearly identical although the boundary conditions (at the edge of the boundary layer and at the centre of the channel) are different. Comparisons with the experiments of Hussain and Reynolds are also presented.     

Effects of DC testing on AC breakdown strength of XLPE insulatedcables subjected to laboratory accelerated aging

The results of a study performed on crosslinked polyethylene (XLPE) insulated cables tested in the laboratory under accelerated conditions are described. URD-type cables rated at 15 kV were aged at 60 Hz, 6 kV/mm, (150 V/mil) and load cycled daily to 90°C conductor, with water inside the pipe and outside of the samples, for periods of up to 3 years. DC testing was performed before and during the aging. An anticipated significant reduction in the AC breakdown strength is observed in control cables (not DC tested), from 44 kV/mm (1100 V/mil) for unaged cables, to 10 kV/mm (250 V/mil), for aged cables. However, there was no further reduction in the AC breakdown strength of cables subjected to DC testing as compared to those that are not tested with DC. It is concluded that AC breakdown strength is not an effective diagnostic tool for determining the effect of DC testing of URD cables aged under the conditions described