Some preliminary results of the fine structure profiles of radio refractivity near the surface at Ota, Southwest Nigeria

Some preliminary results are presented of the fine structure profiles of surface radio refractivity, Ns, over Ota, Southwest Nigeria (6° 42'N, 3° 14'E) computed from in-situ, one minute interval measurements of surface pressure, temperature and relative humidity. A wireless Davis Vantage Pro2 Weather Station instrument installed at the Department of Physics, Covenant University, Ota in April 2012, was used to obtain the measured variables. Hourly, daily and monthly average values of surface water vapour density, dry, wet and total radio refractivity were obtained for the months of April 2012 to March 2013. The distance to the radio horizon for a given transmitter height may be deduced from the observation that Ns is well correlated with the gradient of refractivity over the first kilometer above ground. Refractivity gradients utilized for the work were those obtained in a previous work for Oshodi, a meteorological weather station near the coast and close to Ota

Between Land and Sky

Stephen Atkinson’s Zachary House can be reduced to four elements as the quote above by Oswald Spengler suggests; each reflects the domestic deities, the spirits of home, and thus becomes symbolic of settlement within a once hostile landscape. Ed. Note: House by Stephen Atkinson; text by William T. Willoughby

Developmental Delays in Executive Function from 3 to 5 Years of Age Predict Kindergarten Academic Readiness

Substantial evidence has established that individual differences in executive function (EF) in early childhood are uniquely predictive of children’s academic readiness at school entry. The current study tested whether growth trajectories of EF across the early childhood period could be used to identify a subset of children who were at pronounced risk for academic impairment in kindergarten. Using data that were collected at the age 3, 4, and 5 home assessments in the Family Life Project (N = 1,120), growth mixture models were used to identify 9% of children who exhibited impaired EF performance (i.e., persistently low levels of EF that did not show expected improvements across time). Compared to children who exhibited typical trajectories of EF, the delayed group exhibited substantial impairments in multiple indicators of academic readiness in kindergarten (Cohen’s ds = 0.9–2.7; odds ratios = 9.8–23.8). Although reduced in magnitude following control for a range of socioeconomic and cognitive (general intelligence screener, receptive vocabulary) covariates, moderate-sized group differences remained (Cohen’s ds = 0.2–2.4; odds ratios = 3.9–5.4). Results are discussed with respect to the use of repeated measures of EF as a method of early identification, as well as the resulting translational implications of doing so

Integrating Item Accuracy and Reaction Time to Improve the Measurement of Inhibitory Control Abilities in Early Childhood

Efforts to improve children’s executive function are often hampered by the lack of measures that are optimized for use during the transition from preschool to elementary school. Whereas preschool-based measures often emphasize response accuracy, elementary school-based measures emphasize reaction time (RT)—especially for measures inhibitory control (IC) tasks that typically have a speeded component. The primary objective of this study was to test in a preschool-aged sample whether the joint use of item-level accuracy and RT data resulted in improved scoring for three IC tasks relative to scores derived from accuracy data alone. Generally, the joint use of item-level accuracy and RT data resulted in modest improvements in the measurement precision of IC abilities. Moreover, the joint use of item-level accuracy and RT helped eliminate floor and ceiling effects that occurred when accuracy data were considered alone. Results are discussed with respect to the importance of scoring IC tasks in ways that are maximally informative for program evaluation and longitudinal modeling

Measuring executive function in early childhood: A case for formative measurement.

This study tested whether individual executive function (EF) tasks were better characterized as formative (causal) or reflective (effect) indicators of the latent construct of EF. EF data that were collected as part of the Family Life Project (FLP), a prospective longitudinal study of families who were recruited at the birth of a new child (N = 1292), when children were 3, 4, and 5 years old. Vanishing tetrad tests were used to test the relative fit of models in which EF tasks were used as either formative or reflective indicators of the latent construct of EF in the prediction of intellectual ability (at age 3), attention deficit/hyperactivity disorder symptoms (at ages 3–5 years), and academic achievement (at kindergarten). Results consistently indicated that EF tasks were better represented as formative indicators of the latent construct of EF. Next, individual tasks were combined to form an overall measure of EF ability in ways generally consistent with formative (i.e., creating a composite mean score) and reflective (i.e., creating an EF factor score) measurement. The test-retest reliability and developmental trajectories of EF differed substantially, depending on which overall measure of EF ability was used. In general, the across-time stability of EF was markedly higher, perhaps implausibly high, when represented as a factor score versus composite score. Results are discussed with respect to the ways in which the statistical representation of EF tasks can exert a large impact on inferences regarding the developmental causes, course, and consequences of EF. More generally, these results exemplify how some psychological constructs may not conform to conventional measurement wisdom

A Simple Resistive Load I-V Curve Tracer for Monitoring Photovoltaic Module Characteristics

Current-Voltage (I-V) curve tracers are useful implements for solar Photovoltaic (PV) research and manufacturing, particularly when wishing to ascertain module yield viz-a-viz solar irradiation falling on the module in different climatic conditions. This paper presents a simple affordable and easy to fabricate instrument for tracing I-V characteristics of a PV module. It comprises of rapidly varying resistive loads centred on power resistors connected to relays and controlled by an electronic circuitry. The circuit consists of a 555 astable oscillator that is used to send clock pulses to the clock terminal of a 4017 decade counter which in turn produces a sequence of pulses. Each progression of pulse advances by one bit to sequentially turn on individual relays via driver transistors. The speed of the count is made variable from the frequency determining network of the 555 oscillator. The I-V characteristics of the module are thus measured by the sequential selection of the relays which are each connected to a selected load resistor to determine the operating point on the I-V curve. The currents and voltages are then recorded simultaneously with irradiance from a pyranometer, by a datalogger to which the instruments are connected. The circuit was tested on two monocrystalline modules to compare the effect of Harmattan dust on PV output yield

Ventilation Optimization — Balancing the Need for More Power Against Environmental Concerns

This paper shows how the Nanisivik mine was able to improve the underground working environment, decrease operational costs, and reduce its impact on the environment through optimizing their ventilation system. Through re-organizing their ventilation system, the overall flow through the mine increased by at least 20%, and local flows increased by over 100%. This change also resulted in a 45% reduction of fan motor power. And as a consequence of reduced power demands the mine has decreased its Green-house gas (GHG) emissions. Currently, ventilation is typically responsible for 40% of a Canadian mine\u27s underground electrical consumption. This could dramatically change as the relationship between air supplied by fans and the power consumed is a cubic. Nanisivik is just one example of how the Canadian mining industry is striving to remain competitive under the general pressures to supply more or better quality ventilation for the workforce but on the other hand reduce power consumption

Sectional Investigation of Seasonal Variations of Surface Refractivity and Water Vapour Density over Nigeria

The accurate knowledge of radio refractive and water vapour density of the troposphere is important in the planning, budgeting and designing of transmission and reception of radiowave signals on earth-space path. Hence, there is the need to adopt more precise techniques to analyze the seasonal variation of refractivity and water vapour density over Nigeria. The seasonal variation of refractivity and water vapour density was studied using thirty-nine years meteorological data for forty-eight (48) stations over Nigeria. The forty-eight stations were grouped into nine vegetation and two major climates in Nigeria. Harmonic analysis approach was used in addition to the monthly mean computation. The results show that Forests zones values of refractivity and water vapour density are higher than Savannahs zones values. The refractivity value increases from about 281 N units at Sudarian Woodland in January to about 383.6 N units at Mangrove station in June. Water vapour density value increases from about 5.18 g/m3 at Brush and Thicket station in November to maximum value of about 22.36 g/m3 at Swamp Forest station in May. Results also show that over 80% variations in refractivity and over 70% variations in water vapour density are revealed in the first three harmonics at all the nine stations. The results indicate that the method of harmonic amplitudes and phases give a more analytical comparison between predictions model and observational data