Theses and Dissertations Collection

Permanent URI for this collectionhttp://


Recent Submissions

Now showing 1 - 3 of 3
  • Item
    Factors affecting the consumption of working time and the strain on the worker in some
    (Sokoine University of Agriculture, 1975) Harstela, Pertti
    The purpose of the study was to formulate an ergonomic model for forest work to serve as frame of reference for theoretical and empirical analysis, to examine the correlations of independent variables in play in forest work such as human, conditions and working method variables with consumption of working time and the physical strain on the worker. The investigation was confined in the empirical material to the cutting of roll-seedlings and the lifting of seedlings in the nursery-, and to the cutting of pulpwood by two working methods, i.e. mediumheavy and heavy work. The final aim was to formulate and test hypotheses of forest work science, postulate new hypotheses and outline an overall theory on the basis of systems analysis. An additional special object was to study the application of the principle of comparative time study in an empirical material and to apply the same principle in pulse rate investigations. This is termed the principle of comparative work study. The work performance was illustrated by a system scheme (Fig. 1). The scheme comprised the following main groups of elements: worker’s inclination for work, working capacity, reflexes and instincts, decision process, environmental factors, working methods and habits, work performance, output, earnings, and effects on the worker. The model was made up parallclly from abstract and concrete concepts, the aim being to make it suitable for the set of concepts of the theory of work study and the level of theory formulation. The model included the feedback from the effects on the worker-sample element group to the worker’s qualities. The literature on forest work studies in which some correlations introduced in the model were investigated is reviewed in Chapter 23. Owing to the great number of output studies they were treated as an example. The greatest part of the research activity has been analysis of the relations between environmental factors — and of them primarily the work difficulty factors — and the work output. The previously outlined system formula is examined in Chapter 24 as a cybernetic, probabilistic system in which the elements as such were conceived to embrace complex linkages and to be of the black-box type. The information transfer of these sample elements was illustrated by only one channel and information was consequently analysed merely as a symbolical expression of space and event. The decision process and the effects of reflexes and instincts were examined as the self-regulatory mechanism of the model. Feedbacks were established both within the worker and between the worker and environment. Principles influencing the formulation of the theory' of work science were postulated on the basis of the general properties of the system, such as threshold values, correlations, the principles of isomorphism and homomorphism: — If a correlation proves to be significant it is relevant at least in the population represented by the material and possibly also in other populations. — On the other hand, if no significant correlation is established between some independent variables there may nevertheless be a significant correlation in some other population or after some threshold values. — Il is useful for development of the theory' to explain the trend of the correlations and the internal conformities to law and mechanism of the elements. — It is assumed hypothetically that the constancy of the relative per-worker working time and strain value is influenced by the difference between the worker’s capabilities that the working methods and working conditions require and by his attitude to the working methods under comparison and his experience. — model taken from nature through simplifications is the more servicable the more deterministic it is. — Empirical work study generally' observes coded messages by indirect means and it is therefore seldom possible to demonstrate direct physiological causal relationships; what results is explanations of the ”either-or” or ”both-and” type. The system description of the work was developed in Chapter 25 by hypothetical insertion in the model of elements formed by the set of concepts of work study principles (Fig. 2). The concepts are: speed of work, physical strain, ratio between physical strain and maximal performance, total strain during the working day, psychic strain, relative consumption of time, average consumption of time, deviation of consumption of time, average strain, deviation of strain, relative strain, and attitudes to work. The quantitative and abstract levels of the concepts of the model were studied using the M-67-meta theory. Fig. 3 shows the concept hierarchies and the measuring features of the concepts. In processing the measuring features for formulation of the theory in the empirical part, concepts of the same quantitativencss arc used which are sub-concepts of the high real theoretical concepts: the worker’s capacity' and inclination for work, effects on the worker, performance, output and environmental factors. Fig. 4 shows the processes as a being model: performance — output and performance — effects on the worker, the worker’s resources (capacity for work) and feelings (inclination for work) and working conditions (environment) which influence the interrelations of these processes. The Jiving organism state of equilibrium. It logical theories that if a was found to be a system which seeks to preserve a was assumed from reference to physiological and psychofactor causes a greater deviation in the equilibrium of the organism than the conditions of other factors, that factor dominates the behaviour of the organism. This theory was applied in the empirical part to explain the phenomena established. In the empirical part the effect was examined of different factors on the consumption of working time, the physical strain on the worker, and the application of certain work study principles in the nursery to the cutting of roJlseedlings, the lifting of pine seedlings and the logging of pulpwood in grapple piles alongside the strip road (working method 2) and a 4-m wide zone for which the bunch size required was reduced (working method 1). The material and the measurements made are described in Chapter 32. The most important results were as follows. Owing to the paucity of degrees of freedom which interfered with testing they were distributed into statistically significant correlations and hypothetical correlations: — Consumption of working time was explained significantly in regression analysis by so-called work difficulty factors, working method, moving speed which illustrates the speed of the work, the time of the working day, the ordinal number of the working day and some independent variables that portray the worker.
  • Item
    Bark-stripping and food habits of blue monkeys in a forest plantation in mount Meru, Tanzania
    (UNIVERSITY OF IDAHO, 1989-04) Maganga, S. L. S
    Bark-stripping of Cupressus lusitanica (cypress) and Pinus patula (pine) by blue monkeys (Cercopethicus mitis kibonotensis) in Meru Forest Plantations has been a problem since they were established in the early 1950s. This study was conducted in 1987 in the Sokoine University of Agriculture determine the magnitude of bark-stripping in relation to the food habits of blue monkeys. assessed in compartments with trees 3 to 14 years old, and the pattern of debarking was monitored throughout the year. On the average, 79.5 % cypress and 88.7% pine trees were debarked. Blue monkeys preferred dominant cypress trees to intermediate trees. In contrast, intermediate pine trees were more damaged than dominant trees. In both species, suppressed trees were least damaged. In all types of trees, the most severe bark damage occurred at the middle and top of the tree trunks. Twisted bole was the most common defect developed by damaged trees; 34% cypress and 38% pine trees were twisted at the middle and top sections. Bark-stripping was low in the rain season and increased in the dry season peaking at 22% of trees damaged in June and July. ■ The food habits data were collected from the indigenous forest at two sites within the plantation. A total of 38 plant species were eaten by blue monkeys. Fruits were the Training Forest, a portion of the Meru Forest Plantations, to The extent, intensity and effects of bark damage were Bark-stripping of Cupressus lusitanica (cypress) and iv most frequently consumed food item and averaged 76% of the monthly feeding records. Leaves were the next important food item but they were inversely related to the feeding on fruits. The other food items (flowers, shoots, petioles and bark) were similarly inversely related to the feeding on fruits. Bark stripping was negatively correlated to the feeding on fruits, and thus increased when the feeding on fruits declined. Fruits of Ficus thonningii were the prime item in the diet of blue monkeys contributing 50 to 60% of the monthly feeding records. The amount of fruit on these trees in the area was also inversely related to extent of bark damage in the plantation. The water and carbohydrate in the bark of cypress and pine trees was determined to examine if they influenced the bark-stripping. These were poorly correlated to the monthly debarking of both tree species.
  • Item
    Carbon storage potential and climate change mitigation: a case of pugu forest reserve, Kisarawe district, Tanzania
    (Sokoine University of Agriculture, 2013) Beda, Goodluck
    Pugu Forest Reserve is a coastal forest covering an area of 2,410 hectares; but has been significantly altered by on-going extraction and conversion to other land uses which releasing carbon dioxide into the atmosphere thus making the forest a net emitter of the greenhouse gases. Though some empirical data exist regarding carbon storage in African coastal forests, little has been done to assess and quantify the carbon stocks and emissions associated with deforestation and/or degradation in all coastal forests, Pugu Forest Reserve inclusive. This study estimated carbon storage of Pugu FR to quantify the above ground carbon in the tree component, the understory carbon components and carbon storage in the soil. An inventory was conducted using a 20m x 40 m (0.08 ha) plots. Above ground tree carbon was determined using an allometric model that uses trees DBH ≥ 5 cm as predictor variable. Carbon storage in litter, herbs and dead wood was determined using Loss of Ignition method, while Walkley-Black method was used to analyse soil carbon. The total carbon density for all 5 pools was 30.95 t C ha-1 equivalents to 113.59 t CO2e ha-1. The mean carbon densities for the above ground components was 6.75 t Cha-1 (24.77 t CO2e ha-1) in which the tree component accounted for 4.5 t C ha -1 equivalent to 16.5 t CO2e ha-1 ( 14.5%); understory components of litter accounted for 0.52 t C ha-1 equivalent to 1.9 t CO2e ha-1 (1.7%); dead wood 1.01 t C ha-1 equivalent to 3.7 t CO2e ha-1 (3.3%), herbs 0.72 t C ha-1 equal to 2.6 t CO2e ha-1 (2.3%) and soil organic carbon stock was 24.2 t C ha-1 equivalent to 88.8 t CO2e ha-1 (78.2%). The mean carbon stored in this forest is lower compared to other coastal forests especially in the above ground component indicating an alarming degradation and destruction. Improved management and restoration of degraded parts can greatly increase the C storage potential and emission mitigation by this forest. Using this information as the baseline carbon stocks; can be potential for participation in carbon trading under the current REDD+ initiatives with contribution to alternative livelihoods and sustainable development to adjacent communities.