Spectral and Economic Efficiencies of Land Mobile Radio Systems

A variety of land mobile radio systems are compared by their spectral and economic efficiencies in providing various user services, system types covered are private one-channel, shared repeater one channel, controlled-access one-channel, trunked multichannel, and cellular. Spectral efficiency is defined to be the number of mobile users that can be served per MHz of spectrum in a core urban area, while economic efficiency is the average system cost per mobile. Both efficiencies vary with the type of usage, hence they are calculated for three major usages-mobile telephone service, dispatch service emergency, and dispatch service nonemergency. Services are described via seven "service parameters," namely call holding time (average), tolerable average wait for channel access, peak busy hour utilization per mobile, audio quality (S/N), noise levels tolerable, and service range. Sensitivity of the basic results to variations in the service parameters are also computed and discussed.     

Amplitude correlations in nuclear resonance spectroscopy

Both magnitudes and relative signs of inelastic decay amplitudes have been measured for proton resonances in the compound nuclei ⁴⁵Su, ⁴⁷V, ⁴⁹V, ⁵¹Mn, ⁵⁵Co, and ⁵⁷Co. Resonances with orbital angular momenta 1,2 and 3 and five different values of J^π were studied. For l = 1 and l = 2 resonances, sample sizes are sufficient to perform statistical analyses: distributions of the reduced widths, distributions of the products of reduced width amplitudes, and both amplitude and widt correlations have been determined over energy ranges of ～ 1 MeV. The distributions are compared with the predictions of random matrix theory, and good overall agreement is obtained. These result have provided new tests of the statistical theory of resonances and of the theory of isobaric analogue states. In addition, these data give the first experimental confirmation of the channel coupling required by direct reaction theory. The linear correlation coefficients are often surprisingly large (for these data sets, the average value is >0.5 ), so large in fact that the traditional DWBA treatment of direct reactions must fail in some cases. This failure is discussed with the aid of a simplified model. Tests of the Gaussian nature of reduced width amplitudes are also examined.     

Relative importance of tropospheric and precipitation scatter in interference and co-ordination

A simple analysis of the magnitudes of tropospheric forward scatter in clear air and scatter from rain shows that, in practice, the former mode need not be considered for interference and co-ordination calculations. The co-ordination area will be determined either by super-refraction or by scatter from rain.     

Absorption mechanisms for waterborne sound in Alberich anechoic layers

The effect of replacing the viscoelastic, polymer, base layer by a metal base on the anechoic performance of an Alberich, underwater, sound absorber is reported. It is seen that anechoic performance can be retained using the metal base and it is concluded that the anechoic behaviour is primarily due to the dynamic behaviour of the cover layer.     

Application of impedance measurements in an investigation of a waveguide thermistor mount

The concept of waveguide impedance is used to develop a simple equivalent circuit for a thermistor bead mounted in the centre of a rectangular waveguide. Impedance measurements on such a mount at a frequency of 3GHz show that the self capacitance of the bead is 0.2?0.3pF. This result affords a possible explanation of the errors experienced with some thermistors when measuring microwave power in terms of a d.c. calibration.     

Fine structure of analogue states

This article reviews all the high-resolution data on fragmented analogue states taken at the Triangle Universities Nuclear Laboratory, over a period of ten years. There are fifty analogue states observed by proton scattering on targets of masses between 40 and 64, and mass 92. The number of fragments may be only two or three, or as many as fifty. Of the total, only 17 states have a sufficient fine structure pattern where an analysis is attempted. In a few cases, inelastic widths and photon and neutron widths are observed besides proton elastic ones. The article discusses the optimum method of analysis of the data with a view to extracting the physical parameters of the analogue: the energy, proton spectroscopic factor, spreading width, shift and asymetry parameter. The last three quantities are discussed from the viewpoint of the Robson model based on one-channel external mixing of the analogue by Coulomb forces. This model has qualitative success, particularly in describing the large asymmetry sometimes seen, but it is not quantitatively adequate. When the proton spectroscopic factors are compared to the neutron counterparts for the parent (as measured by (d,p) studies), after allowing for Coulomb effects, the proton ones are smaller by an amount which increases to 30% in the heavier nuclei (Ni,Mo). This is in line with the situation on ^{2 0 8}Pb. Thus it seems that the inadequacy of a Coulomb explanation of the analogue-parent energy shift (the Nolen-Schiffer anomaly) has a counterpart in the spectroscopic factors.