A procedure for estimating global solar radiation from sky cover is developed from the records of 47 stations in the United States with long periods of radiation observations during the 10-year period, March 1961 through February 1971. It fits a general parabolic equation of the form Y --B + (1 -B)(I -N) P to the observations, where Y is the observed global solar radiation divided by clear sky radiation and N is the sky cover. The variables B (the point at which the parabola crosses the y axis) and P (a variable parameter less than 1.0) are selected to minimize the sum of the errors (Y -Yc.•c) •', where Yc.• is the calculated value of Y. The equation Y -B + (1 -B)(I -N) ø'6• is selected as most representative, and the B values in this equation that minimize the sum of the errors squared for the individual stations are shown in Figure 1. The average absolute error of the 5306 data points is 1.18 MJ m -2, or 7% of the average observed radiation. Because of the uncertainties of the observed global solar radiation and observed sky cover, the procedure should be used with caution, particularly for periods of less than I month. [NTRODUCTION X•r = 1/N(Srad/Crad q-N -1 ) (3) Engineers and hydrologists are frequently faced with the problem of estimating global solar radiation for a point where no measurements of radiation are available. Due to the limited number of stations in the United States where global solar radiation is measured it usually is necessary to estimate the radiation from percent of possible sunshine or sky cover. Hamon e! al. [1954] developed a graphical method for converting percent of possible sunshine into daily values of incident solar radiation for stations between 25øN and 50øN. Larnoreaux [1962] used this relation in his work of adapting modern evaporation formulae for use with computers. Baker and Haines [[969] attempted to expand the solar radiation network through correlation of radiation data with frequently
The automation of a library that basically aims at improving the management of the library's resources and increasing access to these same resources by users has caught on so well in the western world that virtually all academic libraries in that part of the world have automated most of their services. In Africa, however, several challenges are making it difficult for academic libraries to do the same, thus depriving them of the numerous touted benefits a library stands to gain from automating its services. The University for Development Studies (UDS) Library in Northern Ghana embarked on an automation project on one of its campuses that has thus far resulted in the full automation of the cataloguing and circulation operations. This article recounts the experiences of the Library in its bid to automate some of its services. The procedures that were followed, as well as the highlights of the automation, are recounted here. Lessons learned and challenges encountered are presented as an example for other academic libraries in Ghana, Africa, and other developing countries that have plans to automate.
University libraries, the world over, are continually striving to ensure timely information access and retrieval. Those at the centre of making this mission possible are the cataloguers. However, because of the nature of the work of cataloguers, very few librarians these days ever aspire to this role. What leads them to become a cataloguer is intriguing. This survey attempts to unravel the mystery about the personal characteristics of head cataloguers of Ghana’s state‐owned university libraries, their continuing professional development and use of information technologies.
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