Engineering software development with HyperCard

The successful and unsuccessful techniques used in the development of software using HyperCard are described. The viability of the HyperCard for engineering is evaluated and the future use of HyperCard by this particular group of developers is discussed

Commentary (Bargaining and Discussion-Is It a Happy Marriage?)

Symposium: A Year of Teacher Bargaining in Indian

Research poster: Climate prediction downscaling of temperature and precipitation in the Great Basin region

Research poste

Unbalanced three-phase distribution system frequency estimation using least mean squares method and positive voltage sequence

The subject of this study is a frequency estimation algorithm suitable for grid-connected power converters placed at a weak coupling point of a three-phase electrical distribution system. An upgraded version of the widely used complex least mean squares (CLMS) algorithm for frequency estimation is introduced to cope with different voltage amplitude unbalance and harmonic distortion levels, both frequently present in power system at distribution level. First, it is suggested that the CLMS algorithm uses only a positive phase-sequence component of voltage vector, the component that is inherently symmetrical and by cancelling the phase unbalance preserves the circular vector trajectory in a two-phase αβ-plane. This study shows that it is even possible to use the positive voltage phase-sequence vector extracted using a constant delay block, thus avoiding potential instability issues in the case of signal frequency feedback loop. Second, possible high signal harmonics and signal measurement noise are both removed using low-pass filters prior to CLMS algorithm deployment. Computer simulations and experiments are performed under a variety of conditions to validate the effectiveness of the proposed technique. Experimental results are achieved using the dataset sampled from the actual three-phase grid voltage at distributed level and with data processing done in the LabVIEW software environment

Stellar Population Models and Individual Element Abundances I: Sensitivity of Stellar Evolution Models

Integrated light from distant galaxies is often compared to stellar population models via the equivalent widths of spectral features--spectral indices--whose strengths rely on the abundances of one or more elements. Such comparisons hinge not only on the overall metal abundance but also on relative abundances. Studies have examined the influence of individual elements on synthetic spectra but little has been done to address similar issues in the stellar evolution models that underlie most stellar population models. Stellar evolution models will primarily be influenced by changes in opacities. In order to explore this issue in detail, twelve sets of stellar evolution tracks and isochrones have been created at constant heavy element mass fraction Z that self-consistently account for varying heavy element mixtures. These sets include scaled-solar, alpha-enhanced, and individual cases where the elements C, N, O, Ne, Mg, Si, S, Ca, Ti, and Fe have been enhanced above their scaled-solar values. The variations that arise between scaled-solar and the other cases are examined with respect to the H-R diagram and main sequence lifetimes.Comment: 33 pages, 13 figures, accepted to Ap

Urban sprawl and microclimate in the Ga East Municipality of Ghana

Climatic elements such as temperature and rainfall provide great and unquantifiable benefits to human health. However, rapid urban sprawl has the tendency to undermine these health consequences. The relationship between urban sprawl and microclimate in the Ga East Municipality has been assessed to present the extent of sprawl that inhibit temperature and rainfall in recent times. Methodologically, satellite imagery and meteorological data (minimum and maximum temperature and rainfall) from 1990 to 2020 were used. The results indicate that rapid urban sprawl in recent times has significantly undermined the local climate through land use and land cover changes. There was strong statistical relationships between temperature and built-up areas (p \u3c 0.05), grass/shrub cover (p \u3c 0.04) and all vegetation cover (p \u3c 0.03). There was also strong statistical relationship between rainfall and built-up areas (p \u3c 0.03), grass/shrub cover (p \u3c 0.04) and all vegetation (p \u3c 0.02). Thus, expansion in built up areas and reduced grass/shrub cover led to increases in temperature, rainfall and surface water run off while reduction in all vegetation led to increase in both temperature and rainfall. These changes in climate brought about by urban sprawl will affect crop production, increase cataclysmic floods as well as growth of some harmful insects. There is the need for the amalgamation of urban growth and climate change into spatial planning through an all-embracing approach