African Journals On-line
Botswana Journal of Technology

Volume 11, Number 2, 2002

Development of science and technology culture among Batswana: a pragmatic approach Omaze.A. Afemikhe

Science and Technology (S & T) are the prime movers of modern development initiatives. For any society and indeed the Botswana one, a citizenry literate in Science and Technology is a must if Science and Technology are to be harnessed for national development. Education and training are necessary imperatives germane to the realisation of this noble goal. This paper presents a pragmatic approach that to our mind can promote Science and Technology culture. The imbuement of such a culture should lead to the production of citizens with requisite skills and knowledge relevant to Botswana science and technology needs. The approach outlined utilises some education and training models and gives evaluation an important role in the endeavour. In addition we have indicated the role of different media and S & T activities in the development and appreciation of Science and technology culture.

Formal specification of a query expression generator using RSL, Cyprian F. Ngolah, William S. Shu and Emmanuel A. Onibere

We design a query generator to convert queries expressed in more user-friendly terms to terms (attributes) that change in line with the underlying database structures of an organisation. These latter terms are generated with the aid of a type structure defined over the database structures and perhaps may be optimised for efficient database access. Formal methods are used for the specification of the query generator which is not the usual practice in the specification of query generators. We use RSL, the RAISE Specification Language, to formally specify our generator. From the specification, an implementation of our generator is generated in C++ using a command within the RSL project support environment that translates RSL to C++. The preliminary results with our generator show that it holds promise as a stand-alone tool as well

Development of software and the design of hardware for the switched mode power supply, H.M.Tulukder, A.V.Gholap and J.Chirima

The design of a transformer and the ratings for the SMPS are possible using the software. The software is capable of handling design data for transformer, rectifier, filter and control unit. It is developed in the “C” programming language for Switched Mode Power Supply (SMPS).

A comparison of ultraviolet radiometers'long-term performance characteristics, P.V.C. Luhanga

In this paper we present a comparison of the performance characteristics of two types of broad-band ultraviolet radiometers. The first type of instrument is manufactured by Eppley Laboratories of the USA and the second type is manufactured by Kipp and Zonen of Holland. The results presented in this paper are for a continuous study period of two years. A comparison of the characteristics of these instruments showed that the Kipp and Zonen instrument has a better long-term performance stability than the Eppley Labs instrument. An additional part of the study was to compare the u.v. radiation to the total radiation received on a horizontal surface for various conditions of the sky, from clear to completely overcast conditions. Observation resulting from this study showed that the ratio of ultraviolet radiation to the total solar radiation was higher for cloudy skies than for clear skies.

The influence of series resistance on the I-V characteristics of CdTe thin films, A.I. Mukolu

The influence of series resistance (R_s) on the current (I) – voltage(V) characteristics of evaporated cadmium telluride(CdTe) thin films has been investigated. CdTe films of thickness 1000Å were deposited by thermal evaporation in a vacuum of about 10^-5torr. For the I – V measurements, the two point probe configuration was adopted using aluminium electrodes. The experiment was conducted in controlled atmosphere where the temperature was varied from 303 to 333k. The I – V measurements reveal that at applied voltages below 40V, the conduction is ohmic while at voltages above 40V, there is departure from linearity due to series resistance. The evaluated values of series resistance vary from 520 to 1000 K as the temperature varies from 303 to 333K. The surface conductance of CdTe increases with temperature according to the relation, = _o exp(-/kT). The activation energy calculated from this empirical relation is 0.7eV. Also, the barrier height of Al- CdTe junction was determined and found to be 0.75eV.

A simplified model for predicting skin dose received by patients from diagnostic x-ray examinations, J.O. Fiase and L.Moalosi

Use of ionising radiation in any sector requires doses to be kept as low as reasonable achievable (ARALA). Thus, in keeping radiation dose to skin from diagnostic X-rays, as low as is required by this philosophy, it is useful to obtain an estimate of skin dose before the actual dose is administered. The aim of this paper is to present a simplified model for predicting skin doses as function of three diagnostic X-ray parameters. The model used was a modification of an existing model by Edmonds. Results obtained based on our model show a reasonable agreement (1% or less) between our modified and the previously existing model. The main advantage of the modified model over the previous model is that the latter is simpler and therefore more convenient to use in routine prediction of skin doses from diagnostic sources.

Radionuclide and mineralogical studies of kimberlite slime and soil samples obtained from the jwaneng diamond mine area, Botswana, J. Gabathuse¹, I.A. Babalola¹ and G. Ekosse²

The -ray spectroscopic and x-ray powder diffraction (XRPD) techniques were applied to study concentrations of three naturally occurring radionuclides: ⁴⁰K, ²³⁸U and ²³²Th and mineral contents in various types of soils and kimberlite slime samples obtained from Jwaneng diamond mine area, Southeastern Botswana. The distribution of the radioactive elements was observed to be uneven due to varying mineralogical compositions of samples. Quartz was the predominant mineral phase in all the samples. Whereas phlogopite, kaolinite, illite, calcite and smectite occurred in minor quantities, lizardite, talc and halloysite were in trace amounts. The annual dose level for the Jwaneng mine was calculated and found to be 0.012 mSv/yr. This baseline is still below the limits given as 50 mSv/yr and 1 mSv/yr recommended by boththe US National Council on Radiation Protection and Measurement (NCRP) and the International Commission on Radiological Protection (ICRP) for workers and members of the public respectively. However, inhalation of mineral dust particles by both workers and inhabitants of the area may constitute health hazards leading to silicosis and related illnesses. Preventive occupational health measures in the mine are continually advised to remain implemented.

Granulometric characterisation of the subsurface sediments around the Gaborone landfill area, BotswanaVeronica M. Ngole¹, Otlogetswe Totolo², Georges-Ivo E Ekosse³

Investigations on granulometric characteristics of the subsurface sediments around the Gaborone Landfill, Botswana were carried out in order to elucidate their implicatory roles on environmental contamination. The particle size (PS) and particle size distribution (PSD), specific surface area (SSA), median diameter (MED) and modal diameter (MD) of 50 subsurface samples collected from the surroundings of the landfill were determined. Results obtained showed a range of 9.82 wt % to 82.8 wt % for sand, 16.44 wt % to 89.64 wt % for silt and 0.00 wt % to 6.73 wt % for clay. Values for SSAs were very low ranging from 0.12 m²g^-1 to 0.56 m²g^-1. The MD and MED lay within the coarse and medium silt range of sediments. These results suggest a subsurface terrain with increased permeability and pore space volume. The sediments are likely to have a low ability to adsorbed contaminants from any plume due to the low clay content and SSA. Based on the granulometric characteristics of the landfill sediments, seepage from the landfill to its surrounding subsurface environment may result in subsurface contamination.

A field performance evaluation of drip emitters: pressure versus discharge, Khumoetsile. B. Mmolawa

Field evaluation of irrigation systems (drip) can form a basis for decision making as to whether the irrigation system needs rehabilitation, overhaul or even dismantling if found to be very uneconomical. A comprehensive field evaluation of irrigation systems involves determining the overall efficiency of the system, for example, determining water use efficiency, field operating efficiency and water management practices in use. However, the objective of this study was to evaluate the operating pressure–discharge relationship for Naan-tif emitters against their manufacturer's recommended pressure-discharge relationship. Three fields in the Gaborone region (Kumakwane, Thamaga, Legotlhong ) were selected for the evaluation. Naan-tif emitters at these fields were evaluated by measuring discharges (volumetric method) from emitters at field operating pressure. The results show that all the Naan-tif emitters evaluated at the three farms had higher average discharge as compared to the manufacturer's recommendation at the field operating pressure. In conclusion, besides pressure fluactuations, clogging of emitters due to poor water quality and poor management practices can also cause emitters to perform outside recommended pressure and discharge values.

Evaluation of a solar crop dryer for rural applications in Nigeria, I.N. Itodo, S.E. Obetta, and A.A. Satimehin

This work is an attempt to exploit the benefits of using forced convection dryers in rural Nigeria by using a photovoltaic powered direct current backward curved centrifugal fan in an indirect solar crop dryer targeted at the subsistent small-scale farmers, who constitute over 90% of the Nigerian farming population. The drying rate, collector and system drying efficiencies were used to evaluate the dryer performance. Temperatures and relative humidity were measured. Corn was dried until no further weight loss occurred. The drying rate of the dryer was 0.74kg/day. The collector and system drying efficiencies were 12% and 10% respectively. The next effort in the development and application of this dryer will be to modify it and obtain better throughput and efficiencies, thereby improving the lot of the rural poor farmers and stimulating the Nigerian economy.

A thermodynamically influenced control for potato storage, C.K.W. Ndiema

One of the major tasks in potato production is the maintenance of storage conditions to ensure minimum post-harvest losses. This should be accomplished at minimum energy costs. In rural stores that are inaccessible to electricity supply, this is entirely achieved by using free movement of outdoor air. However, in major commercial potato stores, circulation of air requires the use of a fan. This paper presents a comparison of the performance of the conventional and modified controllers in reducing mass loss in the bulk and fan energy input. A test stand was constructed for controlled ventilation of a sample of potato bulk under the given ambient conditions. The results obtained show that the modified control achieved reduced mass loss by about 5% while the fan energy input was reduced by up to 10%. It is therefore possible to achieve improved control of the potato storage condition by modifying the controls to operate on the basis of thermodynamic state diagrams.