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A study of quality and efficiency of the printing industry in Tanzania
(University of Dar es Salaam, 199) Bundara, M. M. P
Most of the knowledge and skills are acquired through printed matter. Therefore printing is important for the development of any nation. Apart from the acute shortage of books, the quality and efficiency of printing in Tanzania is deteriorating. The present study which was mainly exploratory was intended to show that, although this trend has always been attributed to age of machinery and lack of inputs, there are many other manageable contributing factors. The influence of quality and efficiency variables like staff skills, environmental conditions, materials and production methods was reviewed and critically examined in the context of the local printing industry. Data on the said variables and an efficiency effectiveness indicators like delivery schedules, magnitude and frequency of printing faults, material wastage and customer complaints were collected and analyzed. The results of the study indicate that all the variables mentioned above may have adverse effects on quality and efficiency of the local printing. Specifically, three major variables were singled out. First since printing is still new to many Tanzanians, customer provide inadequate specifications that can produce the desired quality. Second, with 97% of the entire workforce being "mediocre professionals" the comprehension and enforcement of the correct working procedures is difficult. And thirdly, the institutional inequality in the marketing of print products results into trading of quality and efficient printing for trade commissions. It is recommended that the establishment of every printer's style of the house; upgrading of staff education and training and the equalization of the "print market" by liberalizing the trade commissions may improve the present quality and efficiency levels. Furthermore, the author feels that the establishment of a graphic school for advanced studies in printing is overdue for the development of the printing industry in the country. The results of the present study has three main contributions. First, being the first major study in printing within the local conditions, the results provide background knowledge for future specific research work in the field. Second, the results are expected to contribute in guiding both customers and printers in the possible requirements for improved print quality and efficiency. And thirdly, the exposure of the "primitive trap technique" (as named by the author) as a possible source of machine downtime may call for increased staff training and close management supervision not only in the printing industry, but also in other industries.
Effects of nitrogen, phosphorus and phosphorus placement methods on the growth and yield of Tomatoes
(University of Dar es Salaam, 1976) Manang, Emiliano Z.
Two experiments were conducted to investigate the effects of nitrogen, phosphorus and phosphorus placement techniques on growth and yield of tomatoes. In the first experiment, rates of 80, 320, and 640kgN/ha applied as calcium nitrate and 40, 160 and 280kg p/ha applied as single superphosphate were used. In the second experiment, the rates were 0, 40 and 80kgN/ha applied as ammonium sulphate and 0, 40, 80 and 120kg p/ha applied as triple superphosphate. The methods of P application were “banding”, “broadcasting” and drilling” Nitrogen significantly increased tomato total yield by more than 20% and the number of truses to the first harvest by 10%. The number of flowers in the first truss, the plant height and tissue nitrogen content were also significantly increased by N applications (P= 0.05). The main effect of P on total marketable and early yields and the plant height were non-significant. Tissue P content, however, increased significantly with increasing rates of P application. The main effect of Pon total marketable and early yields and the plant height were non-significant. Tissue P content, however, increased significantly with increasing rates of P application. The NP interaction on mean fruit weight was significant (P= 0.05) Though effects due to methods due to methods of P application were non-significant “banding” seemed to be superior while “drilling” was least effective in respect to most of the parameters studied. Approximately 17% and 11% of the total fruit yield were ventrally and concentrically cracked, respectively. The cracking that occurred on the tomato fruits seemed to be related to the adverse weather conditions that prevailed during the period of field experimentation. For tomatoes grown in soils with characteristics similar to those under which this trial was conducted rates of 80 kg N/ha and 40kg p/ha would seem adequate. When the fifth leaf from the plant apex is sampled at flowering stage the data on plant tissue analysis indicate that values of 4% total N and 0.35% P in the leaf were critical for tomato plant growth. Depending on the characteristics of the soil this technique could be used to assess nutrient requirements of tomatoes.
Solar drying of indigenous vegetables using enclosed convectional solar driers
(University of Dar es Salaam, 1977) Maeda, Elimosaria E.
Four indigenous vegetables were solar dried in three enclosed driers of similar design and dimensions that differed in secondary features which were intended to test the shading and black coating effects on the drier performance. The driers’ performance with respect to drying rate and retention of ascorbic acid and total carotene was compared to drying in the open sunshine. The moisture content in the external air, drying air and out-going air were read from Moillier diagram using wet bulb and dry bulb temperature data. The average temperatures at the driers’ outlets were higher than the temperatures of the drying air. Shading significantly depressed the temperature of the drying air by 8.36-+2.05Oc indicating that the temperature of the drying air was to a large extent dependent on the insolation arriving at the driers base. Drying efficiency was relatively higher in the driers without shade than in the shaded drier, although there were no significant differences in the moisture content of the drying air and the mean wet bulb depressions at the driers’ outlets. Drying efficiency in the enclosed driers was greater than in the open sunshine. Black paint did not significantly increase the temperature of the drying air. The optimum blanching times for fresh Ameranthus sp. And Ipomea batatus leaves were 0.50 and 0.80 minutes respectively. Direct immersion of Vigna unguiculate leaves ib boiling water for up to 12 minutes did not inhibit peroxidase whereas Manihot dulcis leaves have been revealed to require no blanching prior to dehydration. Blanched Amaranthus sp. And Ipomea leaves had mean ascorbic acid content ranging from 5.05 – 11.67 and 18.93 – 22.53mg per 100g dry matter respectively whereas in non-blanched Nanihot dulcis and Vigna unguiculate the means ranged from 180.08 – 415.85 and 93.14 – 179.04mg per 100g dry matter respectively; in all cases the highest mean represented amounts retained in vegetables dried in the drying system with shade. Drying under shade also promoted the highest carotene retention. Although drying under shade had a sparing effect on carotene and ascorbic acid, the retained quantities represented relatively low percentages of the content in fresh leaves. Sulphating of non-blanched Manihot dulcis was effective at 400ppm so2 in increasing the ascorbic acid available lyaine by 1.25 and 35.98 per cent respectively while the presence of sulphite ion had a negative effect on carotene retention. The analysis of the amino acid content in fresh and dried vegetables indicated losses in lysine methionine and hictidine. The quantity of retained lysine was however greater than the lysine content in the FAO reference protein.
Residual shear strength of tropical soils.
(University of Dar es Salaam, 1977) Kyulule, Ananias L.
For many years failure of slopes and earth-structures has been a matter of concern to civil Africa where little investigation (if any) has been done so far to combat these problems. To obtain economical and satisfactory results an engineer involved in handling landslide, slope instability and embankment design problems should have the knowledge on residual strength of soils. This research has been carried out, therefore, in order to obtain some residual strength values of tropical soils as a start to tackle such problems. A literature review on residual strength of clays from temperate zones is presented and discussed in this paper. Since residual strength values obtained in temperate countries using the ring shear apparatus are quite reliable and easy to analyse, it was decided to use the same device for this purpose. Eleven soils samples mainly from Tanzania and few from West Africa have been investigated in the Soil Mechanics Laboratory of the University of Dar Es Salaam. These soils are bentonite, black cotton soil, pumice, volcanic ashes, lateritic soil, micaceous soil, Accra shale and weathered mudstone. The descriptions and properties of the soils are also presented. Also presented in this paper is the general layout of the ring shear apparatus as assembled in the Faculty of Engineering, Dar Es Salaam. Essentially the apparatus consists of divided confining rings (outer diameter = 24cm, inner diameter = 16cm) and the sample thickness is 16mm. The testing techniques are fully narrated in the text. Only remoulded samples have been tested. The results of ring shear tests and a discussion on them is also presented in the paper. The residual shear strength values of tropical soils cover a wide range. Bentonite and black cotton soil exhibit angles of residual shear strength fr of about 8.50 and 110; brittleness indices (IB) of 57% and 50% respectively. The Accra shale and weathered mudstone give somewhat higher fr values (»220) and much lower IB value (16-34%). The highest fr values (»300) and the lowest IB values (<2%) are given by volcanic ashes and residual soils (lateritic and micaccous soils).
Man-made lakes: their social economic and ecological impacts: the case in Tanzania
(University of Dar es Salaam, 1977) Kaduma, Josephine Diana
The creation of man-made lakes have become a popular method of developing the water resources of river basins the world over. The purposes for their creation vary from flood control, irrigation, navigation, fishing and hydro-electric power production. Their impacts to the people and areas in their vicinity are similar. The planning, construction, operation and maintainance procedures are also similar. Hence earlier cases provide useful lessons to the later ones. This study examines the influence of man-made lakes on man's environment and on his social and economic ways of life. While man-made lakes have been constructed successfully in some developed nations, in Africa, their planning has omitted many social and environmental aspects. Consequently, various problems to both the people and the economic and / or ecological planners have been experienced. By studying five large man-made lakes in other African countries, the thesis shows how their planning and problems are similar to those of man-made lakes in Tanzania. Nyumba ya Mungu lake, the first man-made lake in Tanzania is studied in detail showing similarities to the five lakes. Its planning and implementation processes are examined showing omissions, failures, successes and achievements. An attempt is made to show where Nyumba ya Mungu experiences are being used in the planning of other man-made lakes in Tanzania and where similar mistakes are being made. The thesis observes with concern that in spite of earlier experiences, planning of new man-made lakes in Tanzania still places a great deal of emphasis on the production of hydroelectric power at the expense of other water requiring activities. The multi-purpose approach is used only as a means of satisfying the economic justification analysis. Pangani and Rufiji river projects are used to illustrate the adherence to this tendency. In an economic analysis, costs and benefits are given monetary values to facilitate comparisons. In a country like Tanzania, it is difficult and sometimes impossible to quantify many benefits accruing from a water resource development project hence the relevance of the analysis becomes questionable.
Rural Electrification and Wind Power in Tanzania
(University of Dar es Salaam, 1978) Reichel, Roland
Present "rural electrification" in Tanzania means supplying electricity to townships and to only a few of the existing 8000 registered villages, which are not yet electrified in any considerable numbers due to technical and economical problems. the initial demand is normally low and the distanceare too great to justify the expenses of transmission lines.Thus individual power stations seem to be the only alternative.Demand figures for typical villages are evaluated, and compared to data from Europe. Out of the alternative sources of energy only one, the WIND ENERGY, is described in some detail. Some wind power theory and brief explanations of windpower terms are given. The status of current Wind powerresearch is described including a list of past and present prototypes.Based on commercially manufactured WIND DIERCY system and careful cost estimations and calculations, two energy supply schemes are proposed: one is for a telecommunication link and the other for a complete village power station of 45 KWrated output. The power station based on wind—energy was found to deliver the electricity at prices cheaper than the diesel—based scheme under certain conditions, working profitable if current electricity celling prices in Tanzania are considered.For wind—power equipment either to be chosen from industrial manufacturers or to be constructed and built in Tanzania, some operating and design criteria are discussed. Results and measured data from own experimental work on: a) Wind—speed measuring equipment b) a three drum SAVONIUS rotor (vertical axis wind—turbine) c) a two bladed horizontal axis wind energy system are presented and briefly discussed, Conclusions are drawn from worldwide—research results and some own calculations as well, Wind- turbines appropriate for villages and possibly small townships as well, in the range of 50 to 200 KWare either manufactured commercially or in the R & D and field test stage, Wind Energy is regarded as one of the clean and inexhaustible sources of energy which is cost—competitive now or in the very near future in industrialized countries, Wind electric systems should thus be given a chance in developing countries as well since they are cost effective, compared to other sources of energy. A market survey listing the present manufacturers of wind power equipment and their programmes is added in the appendix
Preliminary plant design and economics for the production of fertilizer-grade urea from ammonia and carbon dioxide
(University of Dar es Salaam, 1978) Swai & Wolfred, H. Njeri Kiragu & J
A urea plant with a daily capacity of 1000MT and a stream efficiency of 300 days per year is proposed. The preliminary plant design and economic evaluation of this venture have been carried out. Survey of urea synthesis processes has shown that the total recycle stami carbon CO2 stripping process is the best choice. Liquid ammonia and compressed carbon dioxed form product urea via an intermediate product, ammonium carbonate. The synthesis section operates at high temperature and pressure. The uncontrolled ammonia and carbon dioxide are separated from the urea solution and recycled to synthesis section in the form of carbonate solution. The urea solution is flash-evaporated, prilled and screened. The undersize and oversize prills are recycled to evaporation as urea solution. We have designed and selected the various pieces of equipment. Consumption of stream (the main utility) is 60,000 kg/hr. it is produced in the bollar as high pressure steam and then stepped down in pressure via the carbon dioxide compressor and power-generating turbines. Total capital estimate is Tsh. 189.8 million. At a local price of urea of Tsh. 1880/ton, the gross income in the first year of operation is Tsh. 564 million against total production cost of Tsh 503.5 million. Broak-even and shut-down points occur at 72% and 50% production capacity respectively. Rates of return on investment before and after income tax are 25.9% and 14.9%. Discounted cash flow rate of return is 23.7%. pay-back periods excluding and including financing interest are 3.8 and 6 years respectively. This venture proves to be very profitable and we recommend that detailed-estimate and final design should be done as soon as possible. Market research and promotion should prece destart-up.
A study of farming systems for small-scale farmers in an important ecological zone in Kabete location Kenya
(University of Dar es Salaam, 1979) Munene, Susan Mary Wambui
This study covers 49 small farms in Kabete Location, Kiambu District, near Nairobi, Kenya, located within a coffee, maize, and grazing area. The major food crops are maize, beans, and potatoes. Coffee is the leading cash crop in the area, but potatoes and flowers are also important on the sample farms. Potatoes had the largest value for crops sold followed closely by coffee and flowers. The major livestock are dairy cows and poultry, and approximately 2 cows on average were kept. In terms of total sales, 80 percent was from livestock and their products, with milk and eggs as the leading items. Most farmers live within 21/2km of a major road and most use human labour with or without public vehicles to transport produce to market. At higher altitudes, potatoes are a better subsistence crop than maize and most of those grown in the area are used in that way. The Kenyan Government has taken a keen interest in promoting potatoes as a gash crops including a sizable breeding programme. This study was designed in part to measure the potential for potatoes as a cash enterprise on smallholder farms. An average farm consists of 4.8 acres, of which 4.5 acres are available for crops, and had 2 adults and g children, of which 2 children did some farm work. About 80 percent of the women worked full-time on the farm and most of the remainder worked part-time, but nearly 60 percent of the men had full-time off-farm jobs. In terms of man-equivalents 1.65 family workers per farm were available, excluding children who worked only during vacations. To meet subsistence requirements, 1.5 acres of a maize-beans intercrop and 1.8 acres of potatoes are needed when based on lower-than average yields. Thus, in normal years, some surplus from these acres would be available for sale. Milk supplied some nutrients as ' most families kept cows. The possible cash enterprises in the area include horticultural crops like onions, tomatoes, carrots, potatoes, and cabbage, and livestock like poultry, breeder sows, baconer sows and dairy cows. The cash incomes from these farms can be greatly increased by combining these enterprises appropriately as in the proposed farm plans in this study which offer improvements over the existing ones. About 55 percent of the sample farmers had farm incomes, which included the value for home consumption, below Kshs. 5,000 and only 24 percent had farm incomes above Kshs. 9,000. Several improvements are required to raise these incomes. There is a need to develop an efficient food market such that farmers can specialise without fear of failing to obtain food if they do not grow any on their farms. The proposed farm plan in this study which does not include restrictions for food production has an income which is 2.6 times that with the highest income plus these restrictions. Roads are needed to ensure produce reaches the market, and inputs are distributed on time. Water is needed for irrigation and for the livestock enterprises. The market for feeds particularly for pigs and poultry needs improvements. Credit for improving small-scale farmers' incomes needs to be looked into as many sample farmers said they lacked money for improvements and 90 percent of them did not use any credit. There is a need for research into optimum plant populations in intercrops and into crop pest control.
An investigation of actual and potential performance of agricultural machinery in the field: a case study at Kilombero Sugar Estate
(University of Dar es Salaam, 1979) Zungo, Salehe Mzee Nassoro Selemani
The study aimed at investigating the actual and potential performance of agricultural machinery in the field, taking Kilombero sugar Estate as a case study. The study revealed out that service ability at Kilombero Sugar Estate was affected mainly by the nature of duties on which the tractors were employed. Service ability ratios of 82% for field and cane transport tractors were observed. As expected service ability decreased to a small extent, with season (approximately 1% per month). The achieved levels of service ability were high and much better than those recorded on some schemes else where eg. In Ghana. Nevertheless these a figure could be improved by: close attention to routine servicing particularly of items with known liability to damage such as the near when hubs and bolts of newer models of tractors; improve spares availability, improve workshop equipment, and employment of more skilled mechanics, possibly achieved through a formalized programme of an the job training. It would seem reasonable to aim at a serviceability ratio of 90% for field operations.
Stability of cut slopes in coastal Tanzania
(University of Dar es Salaam, 1979) Lucas, R. O
It appears that no standard tangible guidance for the design of cut slopes is available at the moment to cater for the soils of the coastal area of Tanzania. Thus a slope stability research was under taken, in which the instability problem was studied, assessed and design guidelines proposed. The research was conducted by a systematic empirical approach. Long term literature confirms that the instability of cut slopes is much more marked in the case of high (H> 5.0 m) slopes than with low (H< 5.0 m) slopes. Thus the instability problem first became appreciable when it was necessary to cut high slopes. This dates back to the early 19th century. during the pioneer railway construction works in the United Kingdom. Initially the problem was solved by trial and error. However, since the introduction of the science of Soil Mechanics some 40 years ago engineers have developed rigorous quantitative analyses of the stability of cut slopes. These methods are based on the characteristic slip surface shapes namely, the plane surface for homogeneous non-plastic granular soils and the logarithmic curve (generally approximated as circular for computations) surface for homogeneous cohesive soils. The empirical approach is based on the critical relationships between slope angles and their corresponding slope heights for each major soil type as observed from the field performances of the existing out slopes. In the tropics, such as the coastal area of Tanzania the soils are in general partially saturated. They are wetted during the rainy seasons, by infiltrating water, only to a limited depth. The depth of wetting in the research area extends to less than 3.0 m into the ground surface. This situation results in shallow failure zones. The analytical methods for slope stability were developed for deep failure zones. Thus these methods are reliable in the cases of shallow zones. On the other hand the empirical adoptable to this condition. Previous researches elsewhere in the tropics have that under these conditions the empirical is superior to the analytical methods. The research area lies coastal belt of mainland Tanzania between 5°15'S 7°50'S; and between longitudes 38°00'E and 39°30'E. It extends as far north as the Pangani river and as far as the Rufiji river. The area is mostly by well developed ne Neogene to recent while the north west area is covered by a crystalline basement. There are three major types in the research area namely the red laterite soil, the mottled clay/clayey sand and the grey clayey sand. These soils represent the different soil of the various stages of the laterization process. Thus the soils were by the Extended Unified Soil Classification System (EUSCS) for leterite soils as CI, SCI and SCI respectively. A total of 49 selected slopes were systematically studied. The field observations showed that slope heights and slope angles had profound effects on the stability of slopes. Out of 26 low slopes studied only 2 had failed by shear and out of 23 slopes, 11 had shear failures and 9 had erosion failures. Of the 22 flat slopes (6<50°) studied shear and one was eroded; and of the 29 slopes (6>50°), 10 failed by the shear and 9 by erosion. For each type slope heights were plotted against their corresponding slope angles. From these plots critical curves were obtained for stable slopes, and guides determined. The mode of application of these design guides are fully explained in the main text. Of the three major soil types the laterite soil was found to be the most resistant to both shear and erosion failures. It is followed in this respect by the grey clayey sand and lastly by the mottled clay/clayey sand. The difference field performances of the various soils were adequately explained by each of the following laboratory comperative tests: suction pressure test, water absorption capacity and the triaxial tests.
Swelling, strength and consolidation characteristics of tropical black clays (Black cotton Soils)
(University of Dar es Salaam, 1980) Sailie, E. Louis
Tropical black clays, also known as black cotton soils, are high volume change soils in which montmorillonite is the principal clay mineral. These soils cause tremendous damage to structures and, in this country, they are undoubtedly the most problematic in civil engineering constructions. In the present research work, an attempt has been made, through careful laboratory experimentation, to establish swelling, strength and consolidation characteristics of black cotton soils in Tanzania; factors influencing them and their relations to significant index properties. The laboratory studies have shown that most black cotton soils are highly expansive, posses low shear strength both at the peak and residual values and are of poor consolidation properties. It has been established that these characteristics are mainly influenced by the potential volume change (type and amount of clay minerals present) and the physical state of the soil. The index of plasticity and the dry density have been found to be the most useful indices for evaluating black cotton soils. Design considerations for the use of black cotton soils both as foundation and construction materials have been presented and discussed.
Sorption and availability of sulphur in some soils of Mbeya region
(University of Dar es Salaam, 1980) Swai, Lobati Salvatory
Sulphur sorption and availability were studied in ten soils from Mbeya Region. The soils contained kaolinite, hydrous iron oxides and amorphous ferrialumino silicate as the dominant clay minerals. The length of equilibration required for a near-complete equilibrium condition in the soils was investigated. A 48-hour equilibration period was found adequate and was used in the sulphate (SO4) sorption study. The soils differed widely in their SO4 sorption capacity. Soils with high SO4 sorption capacity had higher positive dpH (pH0.1nK2SO4 pH0.1N KCl) values than those with low capacity. The correlation between amount of SO4 sorbed and total Fe203, amorphous Fe203, amorphous ferrialumino silicate or organic carbon content of the soils was statistically non-significant. The SO4 sorption data for most of the soils fitted the Freundlich model. In a greenhouse pot experiment, alfalfa (Medicago sativa) was grown on eight soils at six S-fertilizer rates corresponding to six adjusted-S (equilibrium S) concentations determined from the SO4 sorption isotherm. On most of the soils, the alfalfa seedlings growing in the control pots showed S deficiency symptoms which disappeared as the plants grew older. Sulphur fertilization increased the dry matter yield of alfalfa significantly on four soils; the increase in yield on the other four soils was statistically non-significant. Sulphur fertilization also increased tissue S and S uptake by alfalfa on all the soils. The external S requirement for 95 percent of the maximum dry matter yield ranged from 0.8 to 8.2 mg S/ml, but it was less than 2.0 mg S/ml on most of the soils. The soil with lowest SO4-sorption capacity had a low (but not the lowest) external S requirement. However, there was no consistent direct or inverse relationship between SO4 sorption capacity and external S requirement. Nine indices of S availability in the soils were evaluated. The phosphate and acetate solutions extracted more SO4-S than 0.01M CaCl2 from all the soils. This indicates that a large proportion of SO4-S in the soils was in the chemi-sorbed form. The only index of S availability that was significantly correlated with the relative yield of alfalfa in the greenhouse experiment was 0.01M CaCl2 extractable S. Therefore, 0.01M CaCl2 was considered most suitable for estimation of available S in the experimental soils. *Ionic forms are used without indication of charge throughout the thesis except where charge indication is essential to the meaning.
Sediment transport in Tanzania rivers (A Comparison between Field Measurements and Theoretical Equations).
(University of Dar es Salaam, 1980) Mtalo, Felix Wenceslaus
By selecting about two to three rivers in Tanzania from which river characteristics and some sediment data exist, checking and comparing field measurements methods and results with theoretical sediment transport formulae, the thesis shall try to criticize the existing data and find out which type of field measurements and theoretical formulae would be technically and economically most suitable to use in Tanzania rivers and others of similar characteristics. At the present stage of development in hydraulics and hydrology, it is possible to determine the total sediment discharge of a river by a large number of methods. The results to be obtained from such studies will be as various as the methods themselves. A number of methods and equations are tested for some rivers in Tanzania, and results compared with actual field measurements. River Rufiji, the largest river in Tanzania is taken as a representative in the field of measurements, results of which are used for recommending suitable formulae for determining sediment in such rivers. A detailed discussion on known equations and their assumptions are included. Finally the Engelund-Hansen total load formula is recommended for rivers of the Rufiji type. Further studies on remaining rivers and equations is recommended.
Evaluation of the UAC tool carrier used in maize production system
(University of Dar es Salaam, 1980) Kwiligwa, Emmanuel Makenzi Bundala
The Uyole Agricultural center (UAC) toolbar was developed to provide an effective animal drawn cultivation and planting device for use in low-rainfall farming systems and capable of manufacture by local artisans. This work describes an essential element of the development process for this tollbar via its evaluation was made in terms of capacity, labour requirement, draught force, costs and weed control compared with conventional methods, Split-plot design in randomized block of two replications was laid out. Main treatments included four tillage systems (hand hoe plus hand planting; moldboard plough plus hand planting; UAC tool carrier tine plus hand planting and UAC tool carrier tine plus planter) while sub treatments included two weeding methods ( hand weeding and UAC tool carrier weeder ). The UAC tool carrier tine plus hand planting, and UAC tool carrier plus planter tillage treatments gave the lowest mean grain yields of maize, there was a significant difference at 1% probability level between tillage means. There was no significant difference between weeding means. The UAC tool carrier planter gave a lower plant population than hand planting. The UAC tool carrier was not effective as a weed control tool on uncultivated plots. It resulted into more weed shoot counts and weed dry weights. There was a correlation between maize grain yield per hectare and weed dry per hectare. The variance ratio was highly significant at 1% probability level showing a sufficiently good fit of regression relationship. The proposed UAC tool carrier system (direct drilling; 1st weeding by hand hoe on maize rows; 2nd weeding by UAC tool carrier weeder; and 3rd weeding by hand hoe) gave the lowest labor requirement ( 46% of the purely labour input system) and increased the area cultivable per farm family. But 1st weeding by hand hoe on maize rows which was intended to be a quick operation was limiting. The proposed systems also gave not only the lowest total costs of maize production per hectare but were one of the systems that gave highest value of day manpower. The draught force of the UAC tool carrier tine was lower than that of the moldboard and ridger even when sweeps are attached on the former. The increase in rake angle did not have a remarkable change on the draught. The sweeps on the UAC tool carrier tine brought about more soil disturbance than without them although they increased the draught force. The unexpectedly high force to overcome rolling resistance was probably due to the size and weight of the UAC tool carrier.
Preliminary plant design and economics for the production of hecogenicacetate from sisal juice
(University of Dar es Salaam, 1981) Mziray, E. D. J
A hecogenin acetate plant with a production capacity of 70kg per day and a working rate of 300 days per year is proposed. In this design the authors have carried out a preliminary plant design and an economic evaluation of the whole project with a view of utilizing as much as possible the locally available raw materials. From the literature survey and information obtained from already existing hecogenin concentrate in the country it is evident that hecogenin acetate can best be obtained by the frothing acid hydrolysis method. Because of the advantages associated with it (clause 2,4) this method has been adopted in this project. Due to negligible pollution problems associated with this industry however an effluents treatment plant has not been included. The total capital investment involved is estimated at Tshs. 48.4 million. The sales price per kilogramme of the product has been estimated basing on total product cost at Tshs. 22492. This gives a scales revenue of Tshs. 473 million during the first year of operation against a total production cost of Tshs. 458 million. A profitability analysis’s has shown the break-even and shut down point to occur at 72% and 56% plant capacities respectively. Rates of return on investment before and after income tax are 46.8% and 24.9%. The payback period based on the total capital investment is only 33 years. With the above results this venture indicates that it may be economically viable and in view of the ease with which the raw materials can be obtained within the country it is worthwhile undertaking. The authors therefore strongly recommend that a detailed design be carried out by the concerned Government Authorities as soon as possible. This will make the country utilize her sisal potentials more profitably.
Preliminary process design development and economics for dry baker’s yeast plant
(University of Dar es Salaam, 1981) Omadi, O. L
Bakers’ yeast is a strategic input in bread manufacture. In this report, the manufacture of dry Bakers’ yeast from molasses which is abundantly available from the cane sugar factories in Tanzania is investigated. Molasses is a principle source of nutrients for the growth of yeast cells but must have a suitable chemical composition for this purpose. Molasses available here is interestingly within the recommended specifications in literature. Back-ground theory on the growth of yeast in relation to the amount of nutrients from the raw materials is given. It is the basis for material and heat balances, equipment design and economics for the process described in this report. At present, all the requirements for Bakers’ yeast in Tanzania are not from imports from Frances, British and W. Germany. On an average, over 100 tons of yeast have been imported annually for the last 6 years. The domestic demand has definitely been higher than the amount imported but does not seem to justify a plant of very large capacity. This report is therefore based on the production of 1 ton of dry yeast per day. A working year is considered to be 300 days and the plant is designed to operate on two shifts per day, employing 17 men (excluding Administrative personnel). It will be situated at a sugar factory site to take advantage of the already existing overhead facilities and services. This is considered to cut down annual operating costs. Only a batch fermentation of molasses solution is considered as the continuous systems are probably more complicated and too expensive for a simple plant of this capacity. The total fixed capital investment is estimated at 23,907,000 Tshs. With annual operating costs for the first year of operation at 5, 512,000 Tshs and rising 10% annually for the next 9 years of plant life. The revenue for the 1st year of operation is 9, 000, 000Tshs and also rises 10% annually. The annual income is taxed 50% at the end of every year and taxation sharts after the 1st year of operation. The plant salvage value is 0 and the plant depreciated linearly over the 10 years of lifetime. The day back period is 7.5 years and Discounted Cash flow rate of return is 5.08%. the breakeven point is 46% plant capacity while the shutdown point is 22% plant capacity. This suggests that the project is viable. Potential investors are very much argued to look into this venture, while the academicians are invariably argued to merge their knowledge with the national attempts to make the project a success.
Preliminary plant design and economics for production of furfural from maize cobs
(University of Dar es Salaam, 1981) Mulamula, T. L
The most important uses of furfural include the following; it is a chemical intermediate selective solvent in the refining of oils, resin former, decolourising agent for wood resin, reactive solvent in the manufacture of retinoid bonded, grinding wheels and extract ant for butadiene. At the moment Tanzania has no industries making direct use of furfural. Because of future potential industries, availability of agricultural wasters as raw materials and considerable earning of foreign currency the authors feels that installation of a furfural plant in Tanzania will be beneficial. A 5000 metric tons per year of furfural production has been proposed. The raw material is maize cobs to be acquired from Arusha Region (the proposed location for the plant). Furfural will be produced by an autocatalytic hydrolysis of maize cobs using superheated steam at high pressure. The block diagram and the flow sheet show the detailed nature of the process. The major equipment used include the hydrolysis reactor the area tropic column, the dehydration column the continuous decanter and the crusher for the maize cobs. There is also a secondary steam generators to make use of heat from the hot vapours coming from the reactor. The other equipments are storage tanks and vessels, heat exchange and condensers. The total capital investment for the plant is estimated to be 406 millions of Tanzania shillings. It has been established that the payout period is 4 years and the discounted cash flow is 18%. The break even and shut down points occur at 47.5% and 28% plant capacity respectively. Therefore the study shows that the project is viable at the proposed capacity and location.
Stability of earth slopes with detailed consideration of sliding failures along TANZAM railway
(University of Dar es Salaam, 1982) Salema, Ladislaus M
Failures of cut and earth fill embankment slopes in the Mlimba-Makambako Section of the Great Uhuru Railway (Tanzam Railway) that occurred in the rainy season (March-April) 1979 were so extensive that the line had to be closed for 30 days while initial remedial works were being undertaken. There being no consistent and comprehensive information available in TAZARA as regards soils classifications, strength parameters and changes in pore water pressures for the main soils in this section has impeded progress of the rectification works. Most of the repairs done on the rail road have been mostly on adhoc basis and on the basis of the expertise of the Chinese Engineers who gathered quite some practical experiences with these soils during the initial construction of the Railway. It has therefore been necessary for the management of TAZARA to hire the services of soils engineering consultancy to carry out a comprehensive study of this particular section and propose definite specifications for the design and construction of remedial works for the failed slopes and stabilization for the unstable ones. To this end M/S Coffey and Partners of Australia are currently engaged in this study. This thesis however is not part of this formal undertaking commissioned by TAZARA as afore-mentioned. It is an independent effort by the author geared to the study of the conditions that generally led to instability of slopes in this area and particularly on the two major slides that occurred at both ends of Kitete station. The thesis covers a general review of the climate conditions of the area, the general review on the state of the art in slope stability analysis beginning with the historical development of various methods of analysis to the present stage of computerised systems of analysis. The route location in this area is studied in relation to the topography and geology with emphasis on the soil formation and pertinent geological features. A review of the design specification of the slopes and subsequent construction is undertaken. The location and types of failures are generally studied and classified in general terms as shallow and medium slides, deep seated side slope slips, base failures, erosion on cuttings, and underground erosion and collapse of grain structure. The post failure investigations entailing boring and logging, measuring of penetration resistance, soil sampling, measurement of ground water level (phreatic surface) in cased boreholes, and laboratory classification and strength tests for the two slides at Kitete station are recorded. The main soil comprises of a three layer system of residual soils, rising out of the weathering of gneisses and granites, that begins at the top with a reddish - brown silty sandy clay followed by a pinkish - purple clayed silty sand which overlies the grayish clayed sand which in turn is next to the weathered rocks. Sixteen samples selected from assumed slip zones are classified and 9 of them are tested on a triaxial cell to determine the strength parameters namely cohesion and internal friction under consolidated undrained conditions. The parameters are found to be related to the types of soils mentioned above with the reddish-brown sandy clay having angles of internal friction ranging from 23.8° to 29.5° and effective cohesion of 52.9 KN/M2 and 39.2 KN/M2 respectively for the naturally formed soils and Ø' = 18.5° with C' =58.9 KN/M2 for the remolded (fill material) sample from same type of soils. The pinkish-purple layers have angles of friction ranging from 25° to 31° and C' = 19.6 KN/M2 and 0 - 9.8 KN/M2 respectively. The greyish soil has a lower angle of friction than the pinkish purple soil. The pore water pressures were also recorded. These parameters are used in the analysis of the stability of the slopes that existed prior to slides No. I and II. The variation of pore pressures and the assumption of various shear cases involving the reduction of effective cohesion to as much as 50% are considered in the stability analyses using a special computer programme and results indicate the conditions of failure of each slide. Proposals are made for the general rectification options of each of these slides.
Lake Malawi/Nyasa: an investigation of the causes of the recent high levels
(University of Dar es Salaam, 1983) Wobusobozi, N. B
The level of lake Malawi rose by over 2.5 metres between 1960 and 1979. Following a slight fall the lake began to rise again and by mid 1980 had risen a further 0.2 metres to a level of 475.85 metres a.s.l, the highest level recorded since the beginning of this century. Because these recent rises are in contrast to the previous long period of relatively stable levels they aroused considerable interest. High lake levels resulted into both flooding and erosion along both the lake and its major outlet, the Shire river. This study examines possible man-made and natural causes for the rises and opts for an increase in over-lake precipitation as the most likely cause. A Quantitative analysis of each of the components of the water balance namely; rainfall, inflow, outflow change in storage and evaporation has been done each as an independent chapter. Lastly, comparison is also made with similar rises in other East African lakes.
Horizontal flow roughing filters for rural water treatment in Tanzania
(University of Dar es Salaam, 1983) Mbwette, T. S. A
The failure of introduction of Slow Sand Filters (SSF) in drinking water treatment in Tanzania was attributed to the practice of designing them to filter raw waters containing high suspended solids loads directly. The subsequent operational difficulties usually resulted in abandoning them. The assessment of suitability of application of Horizontal Flow Roughing Filters (HRF) as an appropriate pretreatment prior to SSF has been done after investigation of the working conditions of a number of SSF at present, execution of field tests and making economic comparisons with chemically assisted sedimentation. Results proved that HRF can bring about considerable improvements of physical and bacteriological quality of water. Although its investment costs are a bit higher than for chemically assisted sedimentation, its annual operational and discounted costs are much less than the latter. HRF are technically and economically suitable for application in rural water supply schemes of Tanzania since they involve the use of only locally available skills and materials. Besides applying them as pretreatment prior to SSF, they can be used as sole treatment units of raw water in conjunction with plain sedimentation or on their own depending on the nature of the raw water sources. Further research is proposed to be done for the sake of increasing the knowledge of treatment processes involved in HRF.

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