VHF command system study

Solutions are provided to specific problems arising in the GSFC VHF-PSK and VHF-FSK Command Systems in support of establishment and maintenance of Data Systems Standards. Signal structures which incorporate transmission on the uplink of a clock along with the PSK or FSK data are considered. Strategies are developed for allocating power between the clock and data, and spectral analyses are performed. Bit error probability and other probabilities pertinent to correct transmission of command messages are calculated. Biphase PCM/PM and PCM/FM are considered as candidate modulation techniques on the telemetry downlink, with application to command verification. Comparative performance of PCM/PM and PSK systems is given special attention, including implementation considerations. Gain in bit error performance due to coding is also considered

A comparison of the radiation tolerance characteristics of multijunction solar cells with series and voltage-matched configurations

The effect of series and voltage-matched configurations on the performance of multijunction solar cells in a radiation environment was investigated. It was found that the configuration of the multijunction solar cell can have a significant impact on its radiation tolerence characteristics

First-principles investigation of magnetism and electronic structures of substitutional 3d3d transition-metal impurities in bcc Fe

The magnetic and electronic structures of $3d$ impurity atoms from Sc to Zn in ferromagnetic body-centered cubic iron are investigated using the all-electron full-potential linearized augmented plane-wave method based on the generalized gradient approximation (GGA). We found that in general, the GGA results are closer to the experimental values than those of the local spin density approximation. The calculated formation enthalpy data indicate the importance of a systematic study on the ternary Fe-C-$X$ systems rather than the binary Fe-$X$ systems, in steel design. The lattice parameters are optimized and the conditions for spin polarization at the impurity sites are discussed in terms of the local Stoner model. Our calculations, which are consistent with previous work, imply that the local spin-polarizations at Sc, Ti, V, Cu, and Zn are induced by the host Fe atoms. The early transition-metal atoms couple antiferromagnetically, while the late transition-metal atoms couple ferromagnetically, to the host Fe atoms. The calculated total magnetization ($M$) of bcc Fe is reduced by impurity elements from Sc to Cr as a result of the antiferromagnetic interaction, with the opposite effect for solutes which couple ferromagnetically. The changes in $M$ are attributed to nearest neighbor interactions, mostly between the impurity and host atoms. The atom averaged magnetic moment is shown to follow generally the well-known Slater-Pauling curve, but our results do not follow the linearity of the Slater-Pauling curve. We attribute this discrepancy to the weak ferromagnetic nature of bcc Fe. The calculated Fermi contact hyperfine fields follow the trend of the local magnetic moments. The effect of spin-orbit coupling is found not to be significant although it comes into prominence at locations far from the impurity sites.Comment: 26 pages, 11 figure

Automatic hyphenation of afrikaans

A Dissertation Submitted to the Faculty of Science University of the Witwatersrand, Johannesburg for the Degree of M aster of Science November 198

The Peculiar Periodic YSO WL 4 in ρ Ophiuchus

We present the discovery of 130.87 day periodic near-infrared flux variability for the Class II T Tauri star WL 4 (= 2MASS J16271848-2429059, ISO-Oph 128). Our data are from the 2MASS Calibration Point Source Working Database, and constitute 1580 observations in J, H and K_s of a field in ρ Ophiuchus used to calibrate the 2MASS All-Sky Survey. We identify a light curve for WL 4 with eclipse amplitudes of ~0.4 mag lasting more than one-quarter the period, and color variations in J-H and H-K_s, of ~0.1 mag. The long period cannot be explained by stellar rotation. We propose that WL 4 is a triple YSO system, with an inner binary orbital period of 130.87 days. We posulate that we are observing each component of the inner binary alternately being eclipsed by a circum-binary disk with respect to our line of sight. This system will be useful in investigating terrestrial zone YSO disk properties and dynamics at ~1 Myr

Procedures to Evaluate Market Pigs

For a number of years there has been a growing demand for a uniform system of market hog evaluation. The pork industry wanted a system where the basic figures from production and carcass information could be combined and results obtained for industry comparison. After 2 years of study by the National Pork Producers Council in cooperation with the American Meat Science Association, a new system of market hog evaluation based on percent or pounds of lean muscle in total carcass weight was initiated. The National Pork Producers Council hopes the system will meet the demands of the pork industry for a uniform evaluation system

Lamb Carcass Value

The value of a lamb carcass depends upon two factors: (1) the quality of the lean and (2) the quantity of retail cuts the carcass will yield. Both of these value-determining chracteristics are estimated by the USDA quality and USDA yield grades

New Pork Industry Problems: PSS and PSE

Over the past decade the swine producer has made tremendous strides in producing leaner and more heavily muscled hogs which yield a higher proportion of their carcass weight in lean edible portion. The modern pig has excelled his ancestry in total performance, growth, feed efficiency and muscle producing ability. Because of the advances made in nutrition, breeding, and management, the meat type pig of today is more efficient than ever be fore in conversion of feed protein to muscle protein. In addition, the environment under which many pigs are raised has been changed from the customary pasture and dirt lot to a mechanically operated confinement system. These changes in production have added some new problems to the swine industry

Development of optical data processing techniques applicable to detection and study of meteor trails

Development of coherent optical data processing techniques applicable to detection of meteor trails and examination of propertie