A wide-range linear delay circuit†

A wide-range linear delay circuit is described. Such circuits have wide applications. The present circuit, which has excellent temperature stability, employs a compensated bootstrap circuit for generation of a linear ramp waveform and a regenerative Schmitt triggor comparator. The circuit provides good performance and sharp waveforms which may be used for triggering other digital circuits directly.     

Experimental Studies on the Self-Shielding Effect in Fissile Fuel Breeding Measurement in Thorium Oxide Pellets Irradiated with 14 MeV Neutrons

The 14 MeV neutrons produced in the D-T fusion reactions have the potential of breeding Uranium-233 fissile fuel from fertile material Thorium-232. In order to estimate the amount of U-233 produced, experiments are carried out by irradiating thorium dioxide pellets with neutrons produced from a 14 MeV neutron generator. The objective of the present work is to measure the reaction rates of 232 Th + 1 n → 233 Th → 233 Pa → 233 U in different pellet thicknesses to study the self-shielding effects and adopt a procedure for correction. An appropriate assembly consisting of high-density polyethylene is designed and fabricated to slow down the high-energy neutrons, in which Thorium pellets are irradiated. The amount of fissile fuel ( 233 U) produced is estimated by measuring the 312 keV gammas emitted by Protactinium-233 (half-life of 27 days). A calibrated High Purity Germanium (HPGe) detector is used to measure the gamma ray spectrum. The amount of 233 U produced by Th 232 (n, γ) is calculated using MCNP code. The self-shielding effect is evaluated by calculating the reaction rates for different foil thickness. MCNP calculation results are compared with the experimental values and appropriate correction factors are estimated for self-shielding of neutrons and absorption of gamma rays.     

A critical assessment of the Q-W relation and a parametrization relation for computing latent heat fluxes over the Indian Ocean

Ten years (1982–1991) of upper air and ocean surface observations over the Indian Ocean from Sagar Kanya and Monex–79 data have been used to examine the relationship between the precipitable water (W) and surface level humidity (Q) on an instantaneous scale. Our analysis of Q and W over the Indian Ocean shows that Q is correlated with Won an instantaneous scale with r=O·44, which is a statistically significant correlation. A regression between Q and W has been fitted and it has been found that a fifth order polynomial yields a lowest root-mean-square (rms) error of I-4gkg- 1 when compared with observed Q using an independent observation. The validity of earlier derived global relation between Q and W has been examined over the Indian Ocean. It has been found that Liu's global Q-W relation gave a large rms error of 4·1 gkg ^-1 when compared with the observed instantaneous Q values over the Indian Ocean. The usefulness of the above derived Q-W relation and an earlier derived relation between the monthly mean Q and W has been examined for the estimation of latent heat fluxes (LHF) over the Indian Ocean using an independent observation. The LHF estimated from the bulk aerodynamic method using all quantities available from ship observations, called the direct method (M1), has been compared with the LHF computed by using a derived Q-W relation (M2). The rms error between MI versus M2 is found to be 56 Wm^-2. The LHF estimated by Liu's Q -W relation, when compared with MI gave an rms error of 155Wm ^-2, which is suggestive of its unsuitability for the estimation of LHF over the Indian Ocean on an instantaneous basis. The difference between the sea surface humidity (Q,) and surface level humidity (Q) has been parametrized in terms of sea surface temperature (SST) and W, both obtainable from satellite sensors. This relation has then been used to compute LHF (M3) and was compared with MI, where it was found that M1 versus M3 gave an rms error of 58Wm^-2. Thus, this study indicates that methods M2 and M3 are found to be more consistent and accurate in nature, and also suggests that it can be further applied to the LHF estimation using satellite based microwave/IR measurements for Wand SST on an instantaneous basis.     

Experimental force modeling for deformation machining stretching mode for aluminum alloys

Deformation machining is a hybrid process that combines two manufacturing processes—thin structure machining and single-point incremental forming. This process enables the creation of complex structures and geometries, which would be rather difficult or sometimes impossible to manufacture. A comprehensive experimental study of forces induced in deformation machining stretching mode has been performed in the present work. A table-type force dynamometer has been used to record the deforming forces in three Cartesian directions. The influence of five process parameters—floor thickness, tool diameter, wall angle, incremental step size, and floor size on the deforming forces—is investigated. Individual as well as combined empirical models of the parameters with regard to the forces have been formed. The results of this study indicate that the average resultant force primarily depends on the floor thickness to be deformed and the incremental depth in the tool path. This could be due to the variation in local stiffness of the sheet with change in floor thickness. The effect of tool diameter, deforming wall angle, and floor size is not significant.     

Computational study on effects of rib height and thickness on heat transfer enhancement in a rib roughened square channel

A computational study was carried out for the heat transfer augmentation in a three-dimensional square channel fitted with different types of ribs. The standard k–ε model and its two variants (RNG and realizable) were used for turbulence modeling. The predictions were compared with available experimental and computational results. Three rib configurations were used in the present study: 90° continuous attached ribs, 60° V-shaped broken attached thick and thin ribs. It was observed that the maximum heat transfer occurs at the normalized rib spacing (p/e) = 10 in the case of 90° attached ribs. The effects of the blockage ratio and rib thickness were investigated for 60° V-shaped broken ribs with Re = 10,000–30,000 and p/e = 10. It was observed that the average Nusselt number decreases with an increase in the Reynolds number for almost all configurations studied in the present study. For the 60° V-shaped broken ribs, increasing the blockage ratio had an adverse effect on the heat transfer. It was also observed that thin ribs perform better than thick ribs.     

THE TEMPERATURE OF BURNING CARBON PARTICLES IN A FAST FLUIDIZED BED OF FINE PARTICLES

The temperature of coarse (6–8 mm) carbon particles burning in a fast fluidized bed was measured. The burning carbon particle was found to be 50–70^°C hotter than the bed solids. The convective heat transfer coefficient on the particle was also measured in a separate experiment to help predict the temperature of the carbon particle using a mathematical model which considered both combustion kinetics and heat transfer on the particle. A good agreement between the predicted and measured values of temperature was found.     

Asynchronous and Switched Oscillations in a Tuned Anode Oscillator†

Experimental characteristics of a tuned anode oscillator coupled to a tuned load have been studied. Two new phenomena observed from these studies aro described. One of the phenomena is simultaneous oscillation at two nonharmonically related frequencies, the other phenomenon is automatic switching from one frequency to the other,     

XPS study of palladium sensitized nano porous silicon thin film

Nano porous silicon (PS) was formed on p-type monocrystalline silicon of 2–5 Ω cm resistivity and (100) orientation by electrochemical anodization method using HF and ethanol as the electrolytes. High density of surface states, arising due to its nano structure, is responsible for the uncontrolled oxidation in air and for the deterioration of the PS surface with time. To stabilize the material PS surface was modified by a simple and low cost chemical method using PdCl₂ solution at room temperature. X-ray photoelectron spectroscopy (XPS) was performed to reveal the chemical composition and the relative concentration of palladium on the nanoporous silicon thin films. An increase of SiO₂ formation was observed after PdCl₂ treatment and presence of palladium was also detected on the modified surface. I–V characteristics of Al/PS junction were studied using two lateral Al contacts and a linear relationship was obtained for Pd modified PS surface. Stability of the contact was studied for a time period of around 30 days and no significant ageing effect could be observed.     

Central banking in a transitory economy: an adaptive control model for India

The purpose of this paper is to formulate a policy model for the Indian economy, incorporating an expectation generating mechanism in a formal way. The aim is to see how policies will change over time when the expectation of the private sector is changing. In a mixed economy planning has to take into account how the private sector formulates and revises its expectation regarding various government policies and their possible impacts on the endogenous variables (or target variables) in the economy. Normally in an economy like India's the government formulates its plan for the public sector over the next five years. The government can regulate the private sector by various means, such as licences, investment quotas, tax-subsidy rates, bank interest rates and by various monetary controls. The private sector, knowing the targets of the government, formulates its own expectations regarding the fulfulments of the targets (because it never expects that the government can fulfil its targets exactly) and possible movements of various policies. It behaves according to its expectations and realization of past expectations and thus allocates its resources. So the optimum design of public policies should be to direct the private sectors towards the desired goals defined by the planners, taking into account the reactions of the private sector. The purpose of public policy in such an environment should be to formulate different central bank policies regarding money stock, credit expansion and components of the money multiplier along with government discount rate, and the exchange rate so that the private sector would react in the desired way, given the goals set by the planners regarding national income, balance of payments, domestic absorptions and prices.