Digital Commons Network^™

Derivation Of An Expression That Defines The Pulling Forces In Relays With Small Operating Gaps, D. J. Chambega

Tanzania Journal of Engineering and Technology (TJET)

This paper derives an expression that defines magnitude of the pulling force developed in relays with small operating gaps, that is, when the length of the operating gap in between the yoke and the armature is small as compared to the area of the poles at the yoke. To obtain the expression, saturation of the core material is not considered. Results from the expression are then compared with those obtained experimentally. The comparison is found to deliver acceptable accuracy.

Discrete Element Modelling Of The Abrasive Dehulling Process Of Sorghum And Millet, E. L. Lazaro

Tanzania Journal of Engineering and Technology (TJET)

The abrasive dehulling process of sorghum and millet was modelled using a three-dimensional discrete element model. The model was validated by comparison between experimental and simulation results. Good correlation between experimental and simulation results was obtained. Several numerical experiments were also carried out using the developed model to investigate the influence of mill and grain parameters on dehulling of sorghum and millet. The simulated results correlated well with experimental results from literature. The developed model therefore provides a simple and cheap tool, which can be used to study the dehulling process in more detail than, is currently possible using the …

Effect Of Moisture And Loading Orientation On The Mechanical Properties Of Sorghum And Millet, E. L. Lazaro

Tanzania Journal of Engineering and Technology (TJET)

Uniaxial compression properties of sorghum and millet grain at different moisture contents (12–25% dry basis) and at different kernel orientation were investigated. These included: modulus of deformability, maximum compressive force, deformation and toughness at grain break point. Individual grain kernels of two varieties of sorghum, (Dionje and Jumbo) and one variety of pearl millet, (IM) at 12, 15, 20, and 25% moisture content dry basis (mc.db), were quasi-statically loaded using a J.J.universal tensile testing machine to their breaking point. The modulus of deformability, maximum compressive force required to initiate grain rupture and the grain toughness (energy absorbed at break point …

Potential For Use Of Sand In Road Construction In Dar Es Salaam And Coast Regions, Mfinanga A

Tanzania Journal of Engineering and Technology (TJET)

Coarse aggregates for use in road construction in Dar es Salaam and Coast regions are becoming increasingly scarce and expensive while sand, which is cheaper, is readily available in the two regions. This research aimed at evaluating the possibility of using quarry sands in the two regions as a major constituent material in bituminous road pavement layers. First, the use of sand in sand-bitumen bases for low and medium trafficked roads was studied. The study then continued with the preliminary evaluation of the possible use of the sands in hot rolled asphalt mixes. Results show that Mbagala sand can be …

Incorporating E-Commerce Technologies Into Small And Medium Manufacturing Industries In Tanzania, M. A.M. Victor

Tanzania Journal of Engineering and Technology (TJET)

Businesses worldwide are making use of the new opportunities which have been brought up by the developments in Information and Communication Technologies (ICTs), particularly the Internet. Big businesses, especially those multinationals in the developed nations have invested heavily on these technologies and they are reaping their benefits. This paper reports on a study conducted to look at the key issues to be considered in order for small and medium enterprises (SMEs) in Tanzania be able to position themselves technologically in what is termed as E-commerce. Cost and benefits, policy, training and infrastructure issues are looked at in this study.

Sustainable Data Acquisition Methods For Road Maintenance Management In Developing Countries, N. K.M. Mushule

Tanzania Journal of Engineering and Technology (TJET)

Whilst it may be argued that manual methods of pavement data collection are subjective, unsafe, involve high personnel costs and have low repeatability, the initial costs of acquiring automated systems coupled with the technology required to operate and maintain them can be prohibitive for most developing countries. Moreover, automatic measurement of surface distress has proved to be a difficult challenge to instrument designers. In many cases, manual methods are the only ones that can be employed. A research project was carried out to design a sustainable data collection scheme for network level management system for developing countries. A simple procedure …

Properties Of Rice Husk Particle Boards Bonded By A Blend Of Tannin-Cnsl Resin, J. V. Tesha

Tanzania Journal of Engineering and Technology (TJET)

There are vast quantities of agricultural residues available in Tanzania. Rice husk being amongst those residues is reported to have low resistance to alkalis, high silica content, and have short fibres. These factors have made rice husks not attractive raw materials in panels’ production. However, it has been demonstrated that rice husks can be used to develop panel products of low cost and good performance if appropriate indigenous technologies and affordable binders that can bind siliceous materials are used.

This paper provides a summary on the study of the effectiveness of the binding characteristics of a blend of natural adhesive …

Pretreatment Of Robusta Coffee Hulls And Co-Digestion With Cow-Dung For Enhanced Anaerobic Digestion, A. K. Kivaisi

Tanzania Journal of Science

The effect of alkali pre-treatment on anaerobic digestion of Robusta coffee hulls with a lignin content of 29% was studied in batch culture at 55˚C. In order to investigate the effect of cow dung in minimising the effect of coffee-based inhibitory compounds, digestion experiments were performed with blends of pre-treated and non-treated coffee hulls and cow dung with 0,5,10,20,30,50,75 and 100% coffee hulls at a total volatile solids concentration of 1.8g/l fermentation volume. Methane production increased with increase in coffee hulls concentration up to 30% for both substrates. The lowest production was observed at 100% non-treated coffee hulls. Methane production …

Assessment Of Wind Energy Potential For Eletricity Generation In Setchet, Hanang, Tanzania, A. S. Kasasi, R. M. Kainkwa

Tanzania Journal of Science

Tanzania depends heavily on hydropower for her electricity demand and experiences power shortage during the dry seasons. Wind energy is proposed as an alternative source of electricity to the fossil fuel generators during the dry season, the latter are normally used to supplement the shortfall in hydro-electricity generation. Fossil fuel generators produce emissions that are toxic and as such degrade the environment. Wind speed data from a site called Setchet is used to illustrate that the available wind energy can be harvested to generate electricity that can supplement the shortfall of electricity. The windy season, which is from July to …

Morphometrics Of The Pancake Tortoise (Malacochersus Tornieri) In Tanzania, J. Kabigumila

Tanzania Journal of Science

Observations were made of the morphometrics of captive pancake tortoise (Malacochersus tornieri) in June 1995. Carapace length ranges for immature tortoises and adult males and females were 50-115, 123-160 and 129-171 mm respectively. The respective carapace widths were 45-90, 97-130, and 92-129 and 97-130 mm. Carapace height ranges were 15-29, 25-40 and 117-159 mm, respectively, while plastron length ranges were 45-110, 108-150 and 117-159 mm. The relationships between carapace length and width (males: y = 13.763+0.639x; females: y = 17.302+0.639x) and height (males: y=6.851+0.170x, females: y = 17.274+0.170x) were isometric and sexually dimorphic in adults. The relationship between carapace length …

Sexual Dimorphism In The Mandibles Of A Homogenius Black Population Of Tanzania, F. M. Fabian, R. Mpembeni

Tanzania Journal of Science

Mandibles of known age and gender from cadavers of Tanzanian Bantu population were studied to determine if the human mandible could be sexually dimorphic in a homogenous population. All mandibles were measured using electronic two-digit millimetre veneer calliper. All of the male (100%) and 96% of the female mandibles were positively sexed. The present study indicates that the mandible of the Tanzanian Bantu population possesses metric parameters that make it sexually dimorphic. More studies, involving other Tanzanian groups, might reveal racial or ethnic differences based on mandibular morphometrics.

Structural Evolution Of The Kilombero Rift Basin In Central Tanzania, A. H. Mruma

Tanzania Journal of Science

Detailed geological and structural investigations at the northwestern scarp of the Cenozoic Kilombero Rift allow the drawing of its structural evolution and establishment of stress conditions that prevailed at the different deformational episodes at this rift zone. The structure, where the northwestern scarp of the Cenozoic Kilombero Rift System is located, starts by ductile deformation of granitic and gabbroic rock masses leading to the formation gneissic fabric and b-mineral lineation in the rocks. This deformation is of Precambrian age (most probably a Pan African deformation) and its kinematics are characterized by 320˚/20˚ tectonic transport direction (λ1). Later the area was …

Effect Of Cement Production On Vegetation In A Part Of Southwestern Nigeria, A. T. Salami, A. I. Farounbi, J. I. Muoghalu

Tanzania Journal of Science

The impact of cement dust emissions from the factory of West African Portland Cement at Ewekoro in Southwestern Nigeria on the surrounding vegetation was investigated. Sample plots of 20 m x 20 m were established at 1 km intervals from the factory site up to a distance of 10 km intervals from the factory site up to a distance of 10 km in the four cardinal directions. Leaves of common species were randomly selected for chlorophyll content analysis, leaf abundance and leaf area measurement. Woody as well as herbaceous species encountered within the established plots were enumerated, while soil samples …

Mechanistic Studies Of Carbon Steel Corrosion Inhibition By Cashew Nut Shell Liquid, J Y N Philip, J Buchweishaija, L L Mkayula

Tanzania Journal of Science

The inhibition mechanism of the Cashew Nut Shell Liquid (CNSL) on SAE 1008 carbon steel corrosion in CO 2  saturated 3% NaCl solutions has been studied by weight loss, UV/VIS and electrochemical techniques. The phenoxide, R-Ar-O- ions from the CNSL inhibitor were found to be responsible for the reduction of the corrosion rate of the carbon steel. Also, it was observed that the surface charge of the carbon steel electrodes was positive with respect to the solutions containing CNSL inhibitor. It is likely that the mechanism of the CNSL inhibitor adsorption involved the electrostatic attraction between the positively charged metal …

Organochlorine Pesticides In Residues In Waters From The Coastal Area Of Dar Es Salaam And Their Effect On Aquatic Biota, H Mwevura, Oc Othman, Gl Mhehe

Tanzania Journal of Science

Water samples from Msimbazi and Kizinga rivers in Dar es Salaam and from the coastal marine environment receiving waters from these rivers were analyzed for various organochlorine pescticide residues using GC-ECD and GC-MS. p,p'-DDE, p,p'-DDT, dieldrin and γ-HCH were the only organochlorine pesticide residues detected at significantly greater concentrations above the detection limits. There was a marked difference in the frequency of pesticide residue detection during the dry and wet seasons. All the wet season samples and 37.5% of the dry season samples revealed presence of p,p-DDE at concentrations ranging from 0.05 to 0.45 mgl-1 and 0.08 to 0.20 mgl-1 …

Preparation And Characterization Of Activated Carbons From Rice Husks And Shells Of Palm Fruits, Jeg Mdoe, Ll Mkayula

Tanzania Journal of Science

Activated carbons from palm fruit shells (PFS) and rice husks (RH) were prepared using physical and chemical activation processes, respectively. The influence of activation time and temperature (in the case of PFS) and impregnation ratio and carbonization temperature (in the case of RH) on the properties of the resultant carbons were studied. In the case of PFS carbons, there were an increase in adsorption capacity and surface areas with increase in activation time and temperature. The surface area ranged between 292 and 642 m2g-1 at temperature range of between 1000 and 1200 K. In the case of RH carbons, surface …

Spatial-Temporal Changes In Phytoplankton Biomass And Primary Production In Chwaka Bay, Zanzibar, M. N. S. Kyewalyanga

Tanzania Journal of Science

Spatial-temporal variations in phytoplankton primary production (PP) and biomass (B) were studied for a period of about one year, from July 1999 to July 2000. In addition, changes in corresponding environmental variables were examined. Sampling took place at two stations in Chwaka Bay, one located in mangrove areas, Station I, and the other in an open area, Station II. Although there were changes both with location and time, there were no clear seasonal trends. Generally, the phytoplankton biomass and primary production (mg C m-3 h-1) were higher at Station I than at Station II. However, specific production, that is, primary …

Absolute Migration And The Evolution Of The Rodriguez Triple Junction Since 75 Ma, D. C. P. Masalu

Tanzania Journal of Science

The Rodriguez Triple Junction (RTJ) is a junction connecting three mid-ocean ridges in the Indian Ocean: the Southwest Indian Ridge (SWIR), the Central Indian Ridge (CIR) and the Southeast Indian Ridge (SEIR). The evolution of the RTJ has been studied extensively for the past 10 Ma and the triple junction is believed to be largely a ridge-ridge-ridge (RRR) triple junction. However, due to the scarcity of data, its configuration prior to that period is poorly understood. The migration of the RTJ in the hotspot reference frame, for the past 75 million years has been mapped, by reconstructing its traces on …

Engineering Geological Mapping Of Dar Es Salaam City, Tanzania, K. A. Msindai

Tanzania Journal of Science

Engineering geological mapping of Dar es Salaam city in Tanzania has been carried out using desk studies supplemented by field reconnaissance as well as limited laboratory tests. Desk studies involved interpretation of medium to large-scale topographical maps, Landsat imagery and sequential aerial photographs from 1953-1990. These studies also evaluated small to medium scale geological, pedological maps together with ground water data from 50 boreholes. Two basic maps were prepared, namely, geomorphological and geological map depicts the spatial extent of the Neogene geological formations. Three distinct sandstone terraces could be distinguished in Dar es Salaam region at 0-15 m and 30 …

Fall Commencement [Program], December 21, 2002, University Of Northern Iowa

UNI Commencement Programs

The program of the commencement ceremonies, including a list of institutional leadership, a list of the departments by college, awards given at the ceremonies, and a list of undergraduate and graduate degree candidates.

Phylogeny Of Acridocarpus-Brachylophon (Malpighiaceae): Implications For Tertiary Tropical Floras And Afroasian Biogeography, Charles C. Davis, Charles D. Bell, Peter W. Fritsch, Sarah Mathews

Faculty Publications

A major tenet of African Tertiary biogeography posits that lowland rainforest dominated much of Africa in the late Cretaceous and was replaced by xeric vegetation as a response to continental uplift and consequent widespread aridification beginning in the late Paleogene. The aridification of Africa is thought to have been a major factor in the extinction of many African humid-tropical lineages, and in the present-day disparity of species diversity between Africa and other tropical regions. This primarily geologically based model can be tested with independent phylogenetic evidence from widespread African plant groups containing both humid- and xeric-adapted species. We estimated the …

A Simple Method For Indexing Powder Diffraction Patterns Of Cubic Materials:(1) Using The Θ-Values Of Reference, Me Kamwaya

Tanzania Journal of Science

From the values of sin2θ taken from powder photographs of the cubic crystal system, a variable constant, K, which is a multiple of (h2 + k2 + l2) can be determined. The smallest value of sin2θ1 gives rise to a multiple of one, two, or three which corresponds to the smallest value of Σhl2 for the primitive, bcc and fcc crystals, respectively. The old assumption that when indexing, the occurrence of numbers of the form (h2 + k2 + l2) = 8n + 7, where n = 0.1.2.3… should cause each of (h2 + k2 + l2) to be multiplied …

Optimization Of Edxrf For The Study Of Heavy Metal Pollution Of Lake Victoria, Nk Mahommed, In Makundi

Tanzania Journal of Science

This study reports on the optimisation and calibration of the Energy Dispersive X-ray Fluorescence (EDXRF) spectrometer installed in the Department of Physics, University of Dar es Salaam. The spectrometer was subsequently utilized to determine concentrations of heavy metals in water hyacinth (Eichhornia crassipes (Mart) Solms.) found growing along the shore of Lake Victoria. The optimal conditions and detection limits were determined experimentally by variation of the excitation parameters. The study found that the use of a collimator with two apertures of diameter 4 mm each placed 8 mm apart and made of materials that do not interfere with elements to …

Comparison Of Various Methods For Estimating Wave Incident Angles In The Nearshore Zone, As Ngusaru

Tanzania Journal of Science

Five different methods were examined for their suitability in estimating the inshore wave incident angles on a nearshore zone with a complex topography. Visual observation provided preliminary estimates. Two frequency independent methods and one frequency dependent method based on current meter measurements were examined. Another frequency dependent method based on collocated bottom pressure and current meter measurements was also examined. The results from all the methods provided a reasonably consistent estimate of the inshore wave incident angles. The frequency independent methods gave exactly the same results while the frequency dependent methods had a 5% relative error among themselves. Between frequency …

The Polarising Effects In Sintered Kaolin, Fm D'Ujanga, Y Kaahwa, L Atteraas

Tanzania Journal of Science

The polarizing effects in sintered kaolin samples were analysed in terms of the sample density (or porosity) using direct current (dc) techniques. More porous samples exhibited higher polarizing effects than the less porous ones. The conduction carriers in kaolin samples at room temperature were found to be mainly electrons, with ionic conduction being enhanced by the moisture content with the pores. The influence of the uniaxial pressure and particle-size on the compacted and sintered density of the ceramic have been studied, and a density-pressure relationship before- and after-sintering conditions obtained

Studies On Benthic Denitrification In The Chwaka Bay Mangrove Sediments, Zanzibar, Sm Mahommed, Rw Johnstone

Tanzania Journal of Science

Denitrification was measured at three sites in a narrow tidal creek in the Chwaka mangrove ecosystem. Denitrification arising from water column nitrate (Dw) was low (< 0.1μM Nm-2h-1) and there was little spatial and seasonal variation in Dw rates in the creek. Coupled nitrification-denitrification (Dn) was found to be low, but within the range measured in other mangrove sediments. Average values ranged from 0.01 to 0.45 μM Nm-2h-1 and showed strong spatial variations. The low denitrifcation rates observed in the creek were possibly as a result of the low availability of NO3 and high C:N values of the organic matter in the sediment. Spatial variations in denitrification rates were due to variations in concentration levels of organic matter and possibly to disproportionate competition for inorganic nitrogen between denitrifiers and benthic autotrophs among sites. There were no seasonal differences in denitrification rates. Results from the present study suggest that sediment denitrification does not play a major role as a sink for N in this ecosystem

Interpretation Of Refelction Seismic Data From The Usangu Basin, East African Rift System, Ei Mbede

Tanzania Journal of Science

Reflection seismic data collected by AMOCO Tanzania Oil Company in the 80s, are herin used to correlate the main Usangu Basin parameters to those estimated from outcrop, gravity and aeromagnetic data. The seismic data are further used to constrain the geometry of crustal extension in this south-western sector of the East African Rift System (EARS) in Tanzania. Three distinct sedimentary packages on top of the basement reflector are interpreted and correlated to the Permo-Carboniferous Karoo rocks, the Jurassic/Cretaceous and Miocene Red Sandstone Group and Miocene to recent Lake Beds in the adjacent Rukwa basin, where the ages of the sedimentary …

Tectonic Setting Of Gabbroic Rocks In The Western Part Of The Lupa Gold Field, South-West Tanzania, Sr Mnali

Tanzania Journal of Science

There is a pronounced occurrence of gabbroic rocks in the western part of the Lupa gold field, SW Tanzania. These rocks occur in the peripheral part around the Saza-Chuya granodiorite with which it makes a gradiational, unchilled contact. The rocks have been altered or metamorphosed to low-grade greenschist facies as indicated by the presence of secondary epidote, penninite, chlorite, sericite and calcite. The majority of major-element oxides show scattered variation trends against immobile elements such as Zr, indicating some degree of element mobility during post-crystallization processes of alteration or metamorphism. Major-trace-element data show that the gabbroic rocks in the study …

Identification Of Mushroom Mycelia Using Dna Techniques, Mhs Muruke, Ak Kivaisi, Fss Magingo, E Danell

Tanzania Journal of Science

The suitability of using DNA techniques in the determination of relatedness of mushroom fruiting bodies to isolated mycelia was examined. Nine isolates of edible mushroom mycelia of general Oudemansiella, Coprinus and Pleurotus were identified using fruiting bodies as references. Polymerase Chain Reaction (PCR) in conbination with Restriction Fragment Length Polymorphism (RLFP) analyses were carried out on fruiting bodies and mycelia of the isolates. The internally transcribed spacer region (ITS) and ribosomal RNA gene (rDNA) was amplified using ITS1 and ITS4 primers. The RLFP analysis was carried out on the regions amplified by PCR from fruiting bodies and the mycelia was …

Mobility And Immobility Of Mid-Ocean Ridges And Their Implications To Mantle Dynamics, Me Kamwaya

Tanzania Journal of Science

In the past two decades, the mobility of mid-ocean ridges relative to the mantle (absolute migration) have been correlated with major observable features, such as, spreading asymmetry and asymmetry in the abundance of seamounts. The mobility of mid-ocean ridges is also thought to be an important factor that influences the diversity of ridge-crest basalts. However, the mobility of mid-ocean ridges have not yet been defined and mapped. The absolute migration of global mid-ocean ridges since 85 Ma has been computed and mapped. Global mid-ocean ridges have migrated extensively at varying velocities during that period. Presently, the fast-migrating ridges are the …