Electricity Intensities of the OECD and South Africa: A Comparison

Improving a country’s electricity efficiency is considered one of the important ways to reduce its greenhouse gas emissions and to meet its commitments concerning climate change mitigation. In this paper, we conduct a comparative analysis between South Africa and OECD members’ total and sectoral electricity intensities. This is done to establish a sense of South Africa’s relative performance in this regard, to ascertain the possible scope for improvement and, if such scope exists, to determine in which of the industrial sectors

South Africa’s Electricity Consumption: A Sectoral Decomposition Analysis

South Africa's electricity consumption has increased sharply since the early 1990s. Here we conduct a sectoral decomposition analysis of the electricity consumption for the period 1993 to 2006, to determine the main drivers of this increase. The results show that the increase was due mainly to output- or production-related factors, with structural changes playing a secondary role. While there is some evidence of efficiency improvements, indicated here as a slowdown in the rate of increase in electricity intensity, it was not nearly sufficient to offset the combined production and structural effects that propelled electricity consumption higher.

The attitude control of a satellite in an elliptic orbit

Attitude control system for satellite in elliptical orbit calculated by linear equations and computer simulatio

Neighboring optimal feedback control of multi- input nonlinear dynamical systems using discontinuous control

Neighboring optimal feedback control of multi-input nonlinear dynamic system

Basic studies in space vehicle attitude control Ninth semiannual status report

Space vehicle attitude control systems - manned space station, satellite in elliptic orbit, and solar perturbation of Mars Orbite

Basic studies in space vehicle attitude control Semiannual status report, Dec. 1966 - Dec. 1967

Nonlinear optimal attitude control of planet pointing space vehicles, and optimal control of satellite trajectorie

Basic Studies in Space Vehicle Attitude Control Tenth Semiannual Status Report, Period Ending Jun. 1966

Nonlinear optimal control of planet-pointing space vehicle, basic methods for attitude control, and satellite orbit theorie

The Effect of Mass Ratio on the Morphology and Time-scales of Disc Galaxy Mergers

The majority of galaxy mergers are expected to be minor mergers. The observational signatures of minor mergers are not well understood, thus there exist few constraints on the minor merger rate. This paper seeks to address this gap in our understanding by determining if and when minor mergers exhibit disturbed morphologies and how they differ from the morphology of major mergers. We simulate a series of unequal-mass moderate gas-fraction disc galaxy mergers. With the resulting g-band images, we determine how the time-scale for identifying galaxy mergers via projected separation and quantitative morphology (the Gini coefficient G, asymmetry A, and the second-order moment of the brightest 20% of the light M20) depends on the merger mass ratio, relative orientations and orbital parameters. We find that G-M20 is as sensitive to 9:1 baryonic mass ratio mergers as 1:1 mergers, with observability time-scales ~ 0.2-0.4 Gyr. In contrast, asymmetry finds mergers with baryonic mass ratios between 4:1 and 1:1 (assuming local disc galaxy gas-fractions). Asymmetry time-scales for moderate gas-fraction major disc mergers are ~ 0.2-0.4 Gyr, and less than 0.06 Gyr for moderate gas-fraction minor mergers. The relative orientations and orbits have little effect on the time-scales for morphological disturbances. Observational studies of close pairs often select major mergers by choosing paired galaxies with similar luminosities and/or stellar masses. Therefore, the various ways of finding galaxy mergers (G-M20, A, close pairs) are sensitive to galaxy mergers of different mass ratios. By comparing the frequency of mergers selected by different techniques, one may place empirical constraints on the major and minor galaxy merger rates.Comment: 16 pages; resubmitted to MNRA

The Specific Globular Cluster Frequencies of Dwarf Elliptical Galaxies from the Hubble Space Telescope

The specific globular cluster frequencies (S_N) for 24 dwarf elliptical (dE) galaxies in the Virgo and Fornax Clusters and the Leo Group imaged with the Hubble Space Telescope are presented. Combining all available data, we find that for nucleated dEs --- which are spatially distributed like giant ellipticals in galaxy clusters --- S_N(dE,N)=6.5 +- 1.2 and S_N increases with M_V, while for non-nucleated dEs --- which are distributed like late-type galaxies --- S_N(dE,noN)=3.1 +- 0.5 and there is little or no trend with M_V. The S_N values for dE galaxies are thus on average significantly higher than those for late-type galaxies, which have S_N < 1. This suggests that dE galaxies are more akin to giant Es than to late-type galaxies. If there are dormant or stripped irregulars hiding among the dE population, they are likely to be among the non-nucleated dEs. Furthermore, the similarities in the properties of the globular clusters and in the spatial distributions of dE,Ns and giant Es suggest that neither galaxy mass or galaxy metallicity is responsible for high values of S_N. Instead, most metal-poor GCs may have formed in dwarf-sized fragments that merged into larger galaxies.Comment: 12 pages (uses aaspp4.sty), 2 figures, 1 table, to appear in the Astrophysical Journa