For mitigating the deleterious effects caused by time-varying multipath fading, most of the modern digital wireless systems employ some sort of diversity combining. Combining of the different diversity branches, however, may be performed either before demodulation (predetection combining), or after it (postdetection combining). It has been shown earlier that postdetection schemes outperform their predetection counterparts for Rayleigh and less-severe-than Rayleigh (e. g. Rician)-fading channels. In this study, the authors consider Hoyt fading that characterises wireless environments experiencing more-severe-than Rayleigh fading, and compare error performance of postdetection combining with the results available for predetection combining. In particular, two of the combining variants namely selection combining and switched combining are investigated, and symbol error probability of a non-coherent M-ary frequency shift keying receiver is derived for independent but not necessarily identical diversity branches. The comparison reveals that postdetection schemes perform better than predetection combiners when the average branch signal-to-noise ratio (SNR) exceeds some crossover SNR.

Simple closed-form expressions of outage probability and moment generating function (MGF) are found for a switch and examine combiner (SEC) operating over independent and identically distributed (IID) Hoyt fading channel. Next, using the derived MGF, symbol error probability (SEP) of different M-ary modulation schemes are calculated. In addition, an analytic framework is presented for calculation of optimum switching threshold that ensures minimum outage probability or minimum SEP. The analysis is quite general in the sense that it covers switch and stay combiner (SSC) and Rayleigh fading as special cases.

The binding energy of a shallow, hydrogenic on-centre impurity in a GaAs–AlxGa1−xAs quantum dot is calculated using the standard variational technique. The effect of band non-parabolicity is considered using the Luttinger–Kohn ‘effective mass’ equation. The electronic energy level and the donor binding energy are computed as a function of the dot size, both in the presence and in absence of the band non-parabolicity effect. Results indicate noticeable differences in two cases, especially for small dots.

In the present paper a simple proof of a theorem of Sargent on CλP-integral of Burkill is given.

AbstractAn attempt is made to investigate the effects of a tilted magnetic field on the size‐quantized levels of quantum wells in ultrathin films of narrow‐gap semiconductors, taking n‐type InSb as an example. It is found that, in general, the energy eigenvalue of the lowest magneto‐size‐quantized level increases with increasing magnetic field and decreases both, with increasing film thickness and with increasing orientation of the magnetic field, for given values of the other parameters. Besides, it is observed that the difference of the energy eigenvalues of the lowest two magnetic sub‐levels of the lowest electric sub‐band reaches a maximum at a given magnetic field, showing a decrease with its orientation, while it increases with the film thickness.

An attempt is made to investigate the effects of a tilted magnetic field on the size-quantized levels of quantum wells in ultrathin films of wide-gap semiconductors, taking n-GaAs as an example. It is found that the energy eigenvalue of the lowest Landau level corresponding to a given electric subband increases with increasing magnetic field, and reaches a maximum corresponding to a given orientation of the field, the dependence being increasingly prominent with increasing size quantum numbers. Besides, the eigenvalue corresponding to the lowest electric subband decreases with increasing film thickness, the rate of decrease being significantly dependent on the magnetic field and its orientation. Der Einflus eines geneigten Magnetfeldes auf die gequantelten Niveaus in ultradunnen Filmen von Halbleitern mit breiter Bandlucke wird am Beispiel des n-GaAs untersucht. Es wird gefunden, das die Energie-Eigenwerte des tiefsten Landau-Niveaus fur ein gegebenes elektrisches Sub-Band mit der magnetischen Feldstarke wachsen und ein Maximum erreichen (fur feste Feldrichtung), wobei die Abhangigkeit mit wachsender Quantenzahl ausgepragter wird. Uberdies nimmt der Eigenwert des tiefsten Subbands mit wachsender Filmdicke ab, wobei die Rate der Abnahme signifikant von Starke und Richtung des Magnetfeldes abhangen.

AbstractAn attempt is made to investigate the effects of size quantization on field emission from ultrathin films of degenerate wide‐gap semiconductors, taking the image force into consideration. It is noted, taking n‐type GaAs as an example, that size quantization enhances the field emission by several orders of magnitude as compared to that of bulk specimens. Such quantization also leads to oscillatory behavior of the emission with changing film thickness and to a significant dependence of the emission on field strength and carrier concentration.

The characteristic assemblage in ore pockets within reconstituted norites is ferrian ilmenite-ilmenomagnetite-spinel. The xenoblastic texture suggests that of many high-grade metamorphic rocks. The field associations, mineralogic assemblage, and composition of individual phases indicate a magmatic origin. The ores probably represent magmatic segregations metamorphosed under granulite facies conditions.

J. C. Bardhan, S. K. Banerji and M. K. Bose, J. Chem. Soc., 1935, 1127 DOI: 10.1039/JR9350001127