Radio Refractivity Gradient in Lower Troposphere & Its Influence on Transhorizon Radiowave Propagation

281-284Based on recent radiosonde data from the India Meteorological Department, which have better accuracy than data available upto 1967, refractivity gradients for three years (1968-70) over the Indian subcontinent have been determined. The influence of high refractivity gradients usually observed in the lower troposphere on radio wave field strength and variability over transhorizon paths is discussed. The gradients in the lower layers, particularly upto an altitude of 250 m were found to be much higher than values determined from the difference between surface refractivity (Ns) and refractivity at 1 km (N1). A significant percent of these were ducting gradients. Field strength observations over three typical transhorizon paths, which were characterized by high level and wide variability for a significant percentage of time, were found to be consistent with these refractivity gradients

A formal verification method of scheduling in high-level synthesis

This paper describes a formal method for checking the equivalence between the finite state machine with data path (FSMD) model of the high-level behavioural specification and the FSMD model of the behaviour transformed by the scheduler. The method consists in introducing cutpoints in one FSMD, visualizing its computations as concatenation of paths from cutpoints to cutpoints and finally, identifying equivalent finite path segments in the other FSMD; the pro-cess is then repeated with the FSMDs interchanged. The method is strong enough to accommodate merging of the segments in the original behaviour by the typical scheduler such as DLS, a feature very common in scheduling but not captured by many works reported in the literature. It also handles arithmetic transformations.