Effect of homogenization heat treatment on the microstructure and heat- affected zone microfissuring in welded cast alloy 718

The effect of homogenization temperature on microfissuring in the heat-affected zones of electronwelded cast INCONEL 718 has been studied. The material was homogenized at various temperatures in the range of 1037 ° to 1163 ° and air-cooled. The homogenized material was then electron-beam welded by the bead-on-plate welding technique. The microstructures and microfissuring in the heat-affected zone (HAZ) were evaluated by analytical scanning electron microscopy (SEM). The grain boundary segregation of various elements was evaluated by secondary ion mass spectroscopy (SIMS). It was observed that the total crack length (TCL) of microfissures first decreases with homogenization temperature and then increases, with a minimum occurring in the specimen heat treated at 1163 °. This trend coincides with the variation in segregation of B at grain boundaries with homogenization temperature and has been explained by equilibrium and nonequilibrium segregation of B to grain boundaries during the homogenization heat treatment. No other element was observed to segregate at the grain boundaries. The variation in volume fraction of phases like δ-Ni₃Nb, MC carbide, and Laves phases does not follow the same trend as that observed for TCL and B segregation at the grain boundaries. Therefore, microfissuring in HAZ of welded cast INCONEL 718 is attributed to the segregation of B at the grain boundaries.     

Palliation of symptomatic adrenal gland metastases by radiotherapy

Whilst adrenal metastases are common in patients with metastatic disease, they are rarely symptomatic. We present a series of seven patients with painful adrenal metastases who were seen in one centre over an 18-month period. All responded to palliative radiotherapy with a reduction in pain.     

Water resources of India—an overview

11. Conclusion India is rich in natural resources, land and water, which however, have to be developed to improve their productivity. With the rising population and efforts on economic development, the problem is extremely important and urgent. Development of water resources is central in this context as water is generally not available where and when required. India’s arid-monsoon climate and geographical features lead to extreme seasonal and spatial variations. Efforts in this direction have been made since time immemorial, but as the overview shows, we have a long way to go.     

Fixed-width confidence interval estimation of the inverse coefficient of variation in a normal population

A sequential procedure is developed in order to construct a confidence interval of “fixed-width and preassigned coverage probability” for the inverse of the coefficient of variation of a normal population. The proposed sequential procedure is proved to be “asymptotically efficient and consistent” in the sense of Chow and Robbins ([1]: Ann. Math. Statist. 36, 457–462 (1965)). Asymptotic distribution of the stopping time is derived.     

Brittle coating studies on fibrous composites

A brittle coating stress analysis technique applicable to orthotropic materials has been developed. The technique has been applied to a unidirectional glass fibre reinforced epoxy. Its behaviour has been studied under uniaxial and biaxial stress fields using cantilever beam specimens and circular disc specimens under diametral compression. Fibre orientation in the specimens has been varied. In each case it has been observed that the cracks represent the direction of principal strains in the specimen material and not the direction of principal stresses. Application of brittle coating techniques has been suggested to establish the direction and magnitude of principal stresses and strains at every point in a problem with unknown stresses and strains.     

Drag reduction by polymer–polymer mixtures

An extensive study on the turbulent drag reduction caused by the various mixtures of polyacrylamide, purified guargum, xanthangum, and their graft copolymers has been conducted at low concentrations and Re = 14,000 using a turbulent flow rheometer. It has been found in most of the cases that the drag reduction caused by mixtures shows a positive deviation from the linearly additive straight line. This effect is more prominent when the drag reduction caused by both the constituents differ appreciably. In most of the cases, the drag reduction caused by the mixtures is higher than the DR caused by either of the constituent polymers; however, the drag reduction caused by the mixture is less than the sum of the drag reduction caused by both the constituents at their respective concentration in the mixture. It has also been noticed that there is no evidence of synergism in these mixtures at low concentrations.     

A novel method for down-conversion of multiple bandpass signals

Simultaneous down-conversion of multiple band-pass signals is desirable for a number of wireless applications. Bandpass sampling technique can be used for this purpose, but it is difficult to implement and has several drawbacks. In this paper we propose a novel front-end technique to directly down-convert multiple frequency- division multiplexed (FDM) signals separated by certain minimum frequency. A special downconversion function is derived to achieve simultaneous downconversion of the received signals. The technique requires simpler bandpass filters and the ADC has a baseband input as compared to bandpass sampling, which imposes strict requirements on bandpass filters and requires an ADC which can handle RF inputs. The performance of the method has been evaluated by simulating a BPSK receiver employing this technique.     

Brittle coating analysis of orthotropic materials

A brittle coating stress analysis technique applicable to orthotropic materials has been developed. The technique has been applied to a unidirectional glass fibre reinforced epoxy. Its behaviour has been studied under uniaxial and biaxial stress fields using cantilever beam specimens and circular disc specimens under diametral compression. Fibre orientation in the specimens has been varied. In each case it has been observed that the cracks represent the direction of principal strains in the specimen material and not the direction of principal stresses. It is also observed that the threshold strain in the coating is not affected by the biaxiality of the stresses in the coating.     

Linear and non-linear optical transmission from multi-walled carbon nanotubes

The multi walled carbon nanotubes grown by the CVD technique were suspended in methanol and their linear and non-linear transmission properties have been studied. It is observed that the linear transmission spectrum, measured in the range 450–1100 nm, depicts features similar to those of single walled nanotubes. The observed features may be well characterized as the van-Hove singularities of the one-dimensional electronic density of states. Further, excellent non-linear optical properties have been observed in these suspensions. Experiments are conducted to study the optical limiting behavior in the visible (532 nm) as well as in the near infra-red (1064 nm) region by using a dual beam pulsed pump-CW probe, technique. The grown multi walled carbon nanotubes show a strong limiting behavior at both of these wavelengths. The recovery time as observed from the probe beam transmission is measured at different values of the incident pulse energy. The results are discussed in the light of the existing results.