Profitability of Cotton on a Pest Management Continuum in Guntur District of Andhra Pradesh

The plant protection response of farmers in the Guntur district of Andhra Pradesh has been examined with particular reference to the adoption of Bt cotton varieties and IPM components. The farmers have been found to follow a wide range of practices to manage the insect pests in cotton. The use of chemical insecticides has accounted for, about 37 per cent of the total variable costs. No significant reduction in plant protection expenditure has been recorded on adoption of Bt varieties without IPM practices. The adoption of IPM practices, however, has led to reduced use of insecticides and increased profitability. The saving on plant protection chemicals has more than compensated the cost of adopting IPM components. Consequently, the net returns have been found increased considerably from cotton cultivation.Crop Production/Industries,

On the Less Known Effects of Environment and Specimen Geometry on Creep Fracture of Nickel Alloys

Attention has been drawn to the fact that during exposure of nickel to air at elevated temperatures, oxygen diffuses through the grain boundary and reacts with carbon forming gas bubbles of carbon monoxide and/or carbon dioxide. Voids are produced due to the high pressure generated by the gas bubbles which cause creep embrittlement. Alloying nickel with 3.8 weight per cent aluminium, which is a stronger oxide forming element as compared to carbon, could not prevent diffusion of oxygen during exposure of the alloy to air at elevated temperatures. The diffusing oxygen reacts even in the Ni-Al-C system, with carbon and forms gas bubbles of CO and CO/sub 2/ which lead to creep embrittlement. The presence of 15 weight per cent chromium in nickel (Inconel 600 and Inconel alloy X-750), however, plays an interesting role on the kinetics of oxygen diffusion. At temperature 1050 degree Celsius and below, during exposure to air at atmospheric pressure, oxygen can diffuse along the grain boundary and reacts with carbon forming gas bubbles of carbon monoxide, where as at 1120 degree Centigrade and above, the formation of 'barrier' oxide scale, chromium oxide, at the surface prevents diffusion of oxygen. On the other hand, the presence of chromium, as observed in Inconel alloy X-750, does not play an effective role in preventing diffusion of oxygen along the grain boundary in poor vacuum. Circumstantial evidence suggests that diffusing oxygen reacts with carbon and forms gas bubbles of CO with consequential creep embrittlement, reduction in creep life and enhancement in creep rate. It has been shown that exposure of the alloy in poor vacuum has a much more damaging effect on the creep properties than that of an atmospheric pressure. It is, therefore, emphasized that exposure of nickel base superalloys to poor vacuum at elevated temperatures must be avoided; in particular this effect is more pronounced in the alloy with thin section size. It is also shown that even in the absence of oxygen interaction prior to creep testing, section size has considerable influence on the creep properties which is believed to be caused by oxygen interaction during creep deformation. For the same section size, the creep properties may be different in specimens of different geometrices. But for the same ratio of cross-sectional area to perimeter (A/P), rupture lifetime becomes independent of specimen geometry. Failure analysis of an aero engine blade has been presented as a case study to emphasize that while designing a component, utmost care must be excercised to avoid thin sections

Effect of Grain Size, Grain Shape and Subgrain Size on High Temperature Creep Behaviour

Several strengthening machanisms, namely solute strengthening, precipitation and fine particle strengthening, grain size as well as shape control and substructure strengthening, have been utilised in the development of creep resistant alloys. Of these, the effect of polycrystal grain size, grain shape and subgrain size on viscous as well as power-law (climb) creep processes are considered here. Viscous creep processes include Nabarro-Herring (N-H), Coble and Harper-Dorn (H-D) creep. N-H and Coble creep processes are strongly influenced by grain size whereas creep rates under H-D creep are independent of grain size. Though it is usually assumed that power-law creep is independent of grain size, in practice it is not so. Several investigations have revealed that power-law creep does depend on grain size. There are detailed and well understood results pertaining to the role of grain size in viscous creep. On the other hand, subgrain size has been seen to have effect only on the climb creep behaviour which is yet to be clearly understood

First report on observation of abnormal creep in a Zr-2.5wt.%Nb alloy at low stresses

Low-stress creep behaviour of a two-phase Zr-2.5%Nb alloy, differently heat treated, has been investigated using helical test specimens. The phase diagram of the α (hcp) + β (bcc) alloy is characterized by the monotectoid reaction at 893 ± 10 K: β1 → (α + β2) where β1 (Zr-20Nb) and β2 (Zr-80Nb) have widely differing compositions. At the creep testing temperature, 818 K, which is close to but below the monotectoid temperature, the creep rate for samples with the equilibrium α + β2 structure has been found to be considerably higher, over an order of magnitude, than that in samples with the metastable α + β1 structure. Microstructural changes accompanying the markedly enhanced creep rate for the α + β2 structure at stresses as low as 1-4 MPa have been explained in terms of the relative stability of the β1 and the β2 phases during the creep process. An attempt has been made to elicit the likely mechanism underlying the observed enhancement of creep rate and the changes in morphology, composition and volume fraction of the β phase

On Silicides in High Temperature Titanium Alloys

High temperature titanium alloys like IMI 685 contain small amounts of silicon (~ 0.25 wt. per cent) to improve creep resistance. Different types of silicides, namely Ti5Si3 (TiZr)5Si3(S1) and (TiZr)6 Si3 (S2), have been observed to precipitate in various silicon-bearing titanium alloys depending upon their composition and heat treatment. The precipitation of silicides, their orientation relationship with the matrix in different alloys, and the beneficial influence of thermo-mechanical treatment on the distribution of silicides have been pointed out. The effect of silicides on mechanical properties and fracture of the commercial alloy IMI 685 is also indicated

Stacking faults in double hexagonal close-packed crystals

Possible deviations in the regular ....ABACA.... sequence of stacking (0004) close-packed planes in the double hexagonal close-packed (d.h.c.p.) structure have been considered. Six intrinsic and one extrinsic type stacking faults have been suggested. The schemes of stacking sequences have been usefully considered in terms of the configurational symbols suggested by Jagodzinski. Extending the Hirth and Lothe procedure, estimates of theoretical fault energies are given in terms of the number of pairs of planes of separation N which are not in the shceme of perfect structure sequence. Relative fault energies have been arrived at reckoning only the first and second nearest neighbour interactions for three ideal situations: (a) the transformation energy of d.h.c.p. structure to either f.c.c. or h.c.p. structure is the same; (b) d.h.c.p. ⇌ f.c.c. transformation occurs; and (c) d.h.c.p. ⇌ h.c.p. transformation occurs

Crystallization and kinetics studies of Ti20Zr20Cu60-xNix (x=10, 20, 30 and 40) metallic glasses

Synthesis and characterization of Ti20Zr20Cu60-xNix (x = 10, 20, 30 and 40) metallic glasses are reported in this paper. Glassy ribbons are produced by rapid quenching using the standard copper wheel roller technique in argon atmosphere. Their structural characterization is carried out by X-ray diffraction (XRD) and thermal behaviour (crystallization) study by differential scanning calorimetry (DSC). Results of XRD on both sides of each ribbon sample confirmed that each sample was indeed amorphous/glassy as only a very broad peak in XRD pattern was observed. Metallic glass Ti20Zr20Cu50Ni10 shows three crystallization peaks in non-isothermal DSC scans while other three samples show only a single crystallization peak. The activation energy of crystallization for each sample has been calculated using three available models, namely, those of Kissinger, Augis-Bennett and Ozawa. All the three models gave nearly similar activation energies for a given sample within 10%

Purging of silence for robust speaker identification in colossal database

The aim of this work is to develop an effective speaker recognition system under noisy environments for large data sets. The important phases involved in typical identification systems are feature extraction, training and testing. During the feature extraction phase, the speaker-specific information is processed based on the characteristics of the voice signal. Effective methods have been proposed for the silence removal in order to achieve accurate recognition under noisy environments in this work. Pitch and Pitch-strength parameters are extracted as distinct features from the input speech spectrum. Multi-linear principle component analysis (MPCA) is is utilized to minimize the complexity of the parameter matrix. Silence removal using zero crossing rate (ZCR) and endpoint detection algorithm (EDA) methods are applied on the source utterance during the feature extraction phase. These features are useful in later classification phase, where the identification is made on the basis of support vector machine (SVM) algorithms. Forward loking schostic (FOLOS) is the efficient large-scale SVM algorithm that has been employed for the effective classification among speakers. The evaluation findings indicate that the methods suggested increase the performance for large amounts of data in noise ecosystems