Joshua O. Owoseni, G. O. Adeyemi, Y. A. Asiwaju-Bello, A. Anifowose
Bivariate correlation and regression techniques were employed to evaluate the relationship between pairs of geotechnical variables for residual lateritic soils derived from three genetic crystalline rocks in Ibadan metropolis, south-western Nigeria. The significance of mean group differences (parent-rock and level of compactive effort) at 5% level of significance was determined using paired t-test analysis. This is with a view to ascertaining the influence of the pedogenic factor of parent rock, percentage fines, and energy of compaction on engineering index properties of the lateritic soils. The clay-size contents had positive correlations with both Optimum Moisture Content (OMC) and plasticity index, and a negative correlation with the Maximum Dry Density (MDD). The MDD and OMC had significant negative and positive correlations respectively with the amount of fines. The amount of fines and Unconfined Compressive Strength (UCS) had significant negative and positive correlations respectively with the California Bearing Ratio (CBR). The study shows significant parent-rock group differences in most engineering properties. The bandedgneiss-derived soils were found to be better engineering soils than the migmatite-gneiss- and quartzite/quartz- schist-derived soils. The modified AASHTO level of compactive effort which produced better compacted soils than the West African level is recommended for the soils. Keywords: Regression analysis, engineering properties, lateritic soils, pedogenic factors
{"title":"Engineering geological assessment of some lateritic soils in Ibadan, south-western Nigeria using bivariate and regression analyses","authors":"Joshua O. Owoseni, G. O. Adeyemi, Y. A. Asiwaju-Bello, A. Anifowose","doi":"10.4314/AJST.V12I1","DOIUrl":"https://doi.org/10.4314/AJST.V12I1","url":null,"abstract":"Bivariate correlation and regression techniques were employed to evaluate the relationship between pairs of geotechnical variables for residual lateritic soils derived from three genetic crystalline rocks in Ibadan metropolis, south-western Nigeria. The significance of mean group differences (parent-rock and level of compactive effort) at 5% level of significance was determined using paired t-test analysis. This is with a view to ascertaining the influence of the pedogenic factor of parent rock, percentage fines, and energy of compaction on engineering index properties of the lateritic soils. The clay-size contents had positive correlations with both Optimum Moisture Content (OMC) and plasticity index, and a negative correlation with the Maximum Dry Density (MDD). The MDD and OMC had significant negative and positive correlations respectively with the amount of fines. The amount of fines and Unconfined Compressive Strength (UCS) had significant negative and positive correlations respectively with the California Bearing Ratio (CBR). The study shows significant parent-rock group differences in most engineering properties. The bandedgneiss-derived soils were found to be better engineering soils than the migmatite-gneiss- and quartzite/quartz- schist-derived soils. The modified AASHTO level of compactive effort which produced better compacted soils than the West African level is recommended for the soils. Keywords: Regression analysis, engineering properties, lateritic soils, pedogenic factors","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"66 1","pages":"59-71"},"PeriodicalIF":0.0,"publicationDate":"2012-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75465033","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Adsorption characteristics of Pb and Cd were conducted on a natural goethite from Kaduna (Niperia) and compared same with a synthetic goethite. The adsorption data was fitted into Langmuir model which gave Langmuir constants k and Xm for Pb and Cd as 4.99 & 2.40 and 1.43 & 1.05 respectively. The adsorption behavior was essentially the same, although, synthetic goethite sorbed a little more metal ion than the natural goethite. This was attributed to the higher proportion of goethite in synthetic than natural goethite per unit mass of sample rather than greater chemical reactivity of the synthetic goethite. The influence of variable pH and adsorbent concentrations on the sorption of Pb and Cd by the natural goethite was studied. Sorption efficiency was greatly governed by pH with nearly 100% adsorption of Pb occurring at initial pH of 5. Generally, Pb was sorbed more strongly with increasing pH from 3 to 5 than Cd and thus poses less environmental threat. Efficient removal of Pb was achieved at lower dose of goethite, as there was no appreciable increase in the amount of Pb adsorbed when the adsorbent dose was increased.
{"title":"THE INFLUENCE OF PH AND ADSORBENT CONCENTRATION ON ADSORPTION OF LEAD AND ZINC ON A NATURAL GOETHITE","authors":"N. Salam, F. A. Adekola","doi":"10.4314/AJST.V6I2.55175","DOIUrl":"https://doi.org/10.4314/AJST.V6I2.55175","url":null,"abstract":"Adsorption characteristics of Pb and Cd were conducted on a natural goethite from Kaduna (Niperia) and compared same with a synthetic goethite. The adsorption data was fitted into Langmuir model which gave Langmuir constants k and Xm for Pb and Cd as 4.99 & 2.40 and 1.43 & 1.05 respectively. The adsorption behavior was essentially the same, although, synthetic goethite sorbed a little more metal ion than the natural goethite. This was attributed to the higher proportion of goethite in synthetic than natural goethite per unit mass of sample rather than greater chemical reactivity of the synthetic goethite. The influence of variable pH and adsorbent concentrations on the sorption of Pb and Cd by the natural goethite was studied. Sorption efficiency was greatly governed by pH with nearly 100% adsorption of Pb occurring at initial pH of 5. Generally, Pb was sorbed more strongly with increasing pH from 3 to 5 than Cd and thus poses less environmental threat. Efficient removal of Pb was achieved at lower dose of goethite, as there was no appreciable increase in the amount of Pb adsorbed when the adsorbent dose was increased.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"39 1","pages":"55-66"},"PeriodicalIF":0.0,"publicationDate":"2010-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73268860","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We report detailed thermodynamic properties of Na in molten Na-Cs alloys obtained by using the simple theoretical model of Heterocordination. This model has been utilized to determine the free energy of mixing, concentration fluctuations in the long wavelength limit Scc (0), the Warren Crowley short-range order parameter, heat of mixing, entropy of mixing and diffusion coefficient. From these thermodynamic quantities we find that Na-Cs exhibits strong deviation from ideality at all the composition, therefore, it is truly a demixing liquid alloy. This conclusion was justified by the plot of Scc (0), which showed that its values are far greater than the ideal values. Qualitative agreement between the calculated and the experimental quantities for most of the thermodynamics properties was also obtained for the liquid alloys. These liquid alloys further exhibit a high asymmetry in their thermodynamics properties such as the Gibbs free energy and its diffusion.
{"title":"Analysis of van der waal equation near the critical point","authors":"A. Boyo","doi":"10.4314/AJST.V6I1.55161","DOIUrl":"https://doi.org/10.4314/AJST.V6I1.55161","url":null,"abstract":"We report detailed thermodynamic properties of Na in molten Na-Cs alloys obtained by using the simple theoretical model of Heterocordination. This model has been utilized to determine the free energy of mixing, concentration fluctuations in the long wavelength limit Scc (0), the Warren Crowley short-range order parameter, heat of mixing, entropy of mixing and diffusion coefficient. From these thermodynamic quantities we find that Na-Cs exhibits strong deviation from ideality at all the composition, therefore, it is truly a demixing liquid alloy. This conclusion was justified by the plot of Scc (0), which showed that its values are far greater than the ideal values. Qualitative agreement between the calculated and the experimental quantities for most of the thermodynamics properties was also obtained for the liquid alloys. These liquid alloys further exhibit a high asymmetry in their thermodynamics properties such as the Gibbs free energy and its diffusion.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75936519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
From an engineering point of view, the fatigue strength variability of cast aluminium alloy components requires a detailed understanding of the inconsistency of cast defect distribution. Cast aluminium alloys are not generally homogeneous; they may contain two or more types of common casting defects, which are gas and shrinkage porosities, oxide films, and inclusions. Each defect type has its own distribution of sizes; and multiple cast components of presumably the same material may have different histories and therefore different cast defect populations. A number of statistical analyses of fatigue data assume that a single distribution of casting defect is present uniformly throughout the cast aluminium alloys. As a result, fatigue data are statistically not correctly described. By relaxing the assumptions of a single cast defect distribution, of uniformity throughout the material and of uniformity from specimen to specimen, Weibull statistical analysis for multiple defect distributions have been applied to correctly describe the fatigue life data of aluminium alloy castings having multiple cast defects competing to initiate fatigue cracks.
{"title":"Multiple defect distributions on weibull statistical analysis of fatigue life of cast aluminium alloys","authors":"C. Nyahumwa","doi":"10.4314/AJST.V6I2.55174","DOIUrl":"https://doi.org/10.4314/AJST.V6I2.55174","url":null,"abstract":"From an engineering point of view, the fatigue strength variability of cast aluminium alloy components requires a detailed understanding of the inconsistency of cast defect distribution. Cast aluminium alloys are not generally homogeneous; they may contain two or more types of common casting defects, which are gas and shrinkage porosities, oxide films, and inclusions. Each defect type has its own distribution of sizes; and multiple cast components of presumably the same material may have different histories and therefore different cast defect populations. A number of statistical analyses of fatigue data assume that a single distribution of casting defect is present uniformly throughout the cast aluminium alloys. As a result, fatigue data are statistically not correctly described. By relaxing the assumptions of a single cast defect distribution, of uniformity throughout the material and of uniformity from specimen to specimen, Weibull statistical analysis for multiple defect distributions have been applied to correctly describe the fatigue life data of aluminium alloy castings having multiple cast defects competing to initiate fatigue cracks.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"143 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77031043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Moisture content of grain is one of the important parameters always considered when deciding the quality and price of grain, at the stage of harvesting, storage, processing and marketing. Grain having excess moisture content, if stored for long duration, will spoil due to insect/fungus infestation. Portable, field usable, and easy-to-use direct moisture (%) display Grain Moisture Meter is a necessity for the benefit of farmers. The types of Grain Moisture Meters available in the market are with look-up tables, which cause inconvenience when carrying out measurements. We have developed a grain moisture meter, which due to its novel design, eliminates this problem and gives moisture (%) directly on a LCD display. The novelty of this instrument is that it is compact, easy-to-use, portable, and field usable. The moisture meter is based on the principle of dielectric constant variations due to change in moisture. Changes of moisture content affect the dielectric constant of the grain, which in turn makes variation in capacitance. The resultant capacitance variation is converted to voltage variation and calibrated in terms of moisture percentage. On the basis of rigorous experiments the meter has been calibrated for wheat, paddy, soybean, sunflower & mustard. However, the user can calibrate the meter at his level for other grains also. The developed instrument is working satisfactorily for all practical purposes in the range of 5-25 % of grain moisture with an accuracy of ± 1% .
{"title":"A low cost field usable portable digital grain moisture meter with direct display of moisture (","authors":"A. K. Rai, Sivadasan Kottayi, S. Murty","doi":"10.4314/AJST.V6I1.55169","DOIUrl":"https://doi.org/10.4314/AJST.V6I1.55169","url":null,"abstract":"Moisture content of grain is one of the important parameters always considered when deciding the quality and price of grain, at the stage of harvesting, storage, processing and marketing. Grain having excess moisture content, if stored for long duration, will spoil due to insect/fungus infestation. Portable, field usable, and easy-to-use direct moisture (%) display Grain Moisture Meter is a necessity for the benefit of farmers. The types of Grain Moisture Meters available in the market are with look-up tables, which cause inconvenience when carrying out measurements. We have developed a grain moisture meter, which due to its novel design, eliminates this problem and gives moisture (%) directly on a LCD display. The novelty of this instrument is that it is compact, easy-to-use, portable, and field usable. The moisture meter is based on the principle of dielectric constant variations due to change in moisture. Changes of moisture content affect the dielectric constant of the grain, which in turn makes variation in capacitance. The resultant capacitance variation is converted to voltage variation and calibrated in terms of moisture percentage. On the basis of rigorous experiments the meter has been calibrated for wheat, paddy, soybean, sunflower & mustard. However, the user can calibrate the meter at his level for other grains also. The developed instrument is working satisfactorily for all practical purposes in the range of 5-25 % of grain moisture with an accuracy of ± 1% .","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"31 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79277358","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The diverse functions of wetlands are being adversely affected by human activities. This paper discusses the impact of these activities on heavy metal loading in different media within the wetlands. Water and sediment/soil samples were taken from areas with active industrial activities and from an area where there is no industrial activity. Sources of water pollution include effluents from a brewery (high pH) and areas associated with tanning activities, sewage treatment plant and former copper smelter (high electric conductivity values). Effluents from a battery assembly plant, water treatment plant, pharmaceutical industry and former copper smelter have relatively high Pb values (up to 1.4 ppm) otherwise most heavy metal concentrations are below maximum acceptable limits for water. This calls for mitigation measures. In sediments, high heavy metal values were associated with battery and metal fabricating industry (Pb), operations involving Zn scrap (Cd), former Cu smelter (Cu, Pb, Ni and Co), tannery and pharmaceutical industry (Cr), and soap and cosmetics industry (Hg). Fish have low levels of Hg. However, fish is known to bioaccumulate Hg through methylation, may cause increase in the Hg in the food chain. Industries which release effluents with high heavy metal contents should treat them before discharge.
{"title":"IMPACT OF INDUSTRIAL ACTIVITIES ON HEAVY METAL LOADING AND THEIR PHYSICO-CHEMICAL EFFECTS ON WETLANDS OF LAKE VICTORIA BASIN (UGANDA)","authors":"A. Muwanga, E. Barifaijo","doi":"10.4314/AJST.V7I1.55197","DOIUrl":"https://doi.org/10.4314/AJST.V7I1.55197","url":null,"abstract":"The diverse functions of wetlands are being adversely affected by human activities. This paper discusses the impact of these activities on heavy metal loading in different media within the wetlands. Water and sediment/soil samples were taken from areas with active industrial activities and from an area where there is no industrial activity. Sources of water pollution include effluents from a brewery (high pH) and areas associated with tanning activities, sewage treatment plant and former copper smelter (high electric conductivity values). Effluents from a battery assembly plant, water treatment plant, pharmaceutical industry and former copper smelter have relatively high Pb values (up to 1.4 ppm) otherwise most heavy metal concentrations are below maximum acceptable limits for water. This calls for mitigation measures. In sediments, high heavy metal values were associated with battery and metal fabricating industry (Pb), operations involving Zn scrap (Cd), former Cu smelter (Cu, Pb, Ni and Co), tannery and pharmaceutical industry (Cr), and soap and cosmetics industry (Hg). Fish have low levels of Hg. However, fish is known to bioaccumulate Hg through methylation, may cause increase in the Hg in the food chain. Industries which release effluents with high heavy metal contents should treat them before discharge.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"49 1","pages":"51-63"},"PeriodicalIF":0.0,"publicationDate":"2010-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89361397","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Solutions chemistry of the rainwater and the unsaturated zone interstitial water of Louga (Northern Senegal) local aquifer provide valuable information related to water-rock interaction occurring during natural recharge. Non reactive chloride ion and rainwater ion/ chloride molar ratios are used as a baseline against which sequential uptake and release of solutes from/to the unsaturated zone solution may be studied. Cation exchange capacity (CEC) and exchangeable cation (EC) experiments, together with chemical analysis of the interstitial water carried out through the entire unsaturated zone profile have revealed that base exchange reactions and dissolution of silicate minerals are the dominant processes controlling the water chemistry. In the uppermost 7 m of the profile, silicate weathering dominates, this process occurs at low pH (3.5 – 4). Major cations and silicium are released to the interstitial water above the calibrated rainwater reference. Below this depth, exchange reactions dominate, they are accompanied by a gradual increase in pH (up to 5). However, ion selectivity reaction seems to control the concentration of the cations. Preference of bivalent cations (Ca2+, Mg2+) over monovalent cations (K+, Na+) by the clay minerals may explain the chemistry of both the unsaturated zone solutions and at the immediate water table.
{"title":"Vertical hydrochemical profiles in the unsaturated zone of louga (senegal) aquifer controlled by geochemical processes","authors":"F. Serigne, C. F. Seynabou","doi":"10.4314/AJST.V6I1.55163","DOIUrl":"https://doi.org/10.4314/AJST.V6I1.55163","url":null,"abstract":"Solutions chemistry of the rainwater and the unsaturated zone interstitial water of Louga (Northern Senegal) local aquifer provide valuable information related to water-rock interaction occurring during natural recharge. Non reactive chloride ion and rainwater ion/ chloride molar ratios are used as a baseline against which sequential uptake and release of solutes from/to the unsaturated zone solution may be studied. Cation exchange capacity (CEC) and exchangeable cation (EC) experiments, together with chemical analysis of the interstitial water carried out through the entire unsaturated zone profile have revealed that base exchange reactions and dissolution of silicate minerals are the dominant processes controlling the water chemistry. In the uppermost 7 m of the profile, silicate weathering dominates, this process occurs at low pH (3.5 – 4). Major cations and silicium are released to the interstitial water above the calibrated rainwater reference. Below this depth, exchange reactions dominate, they are accompanied by a gradual increase in pH (up to 5). However, ion selectivity reaction seems to control the concentration of the cations. Preference of bivalent cations (Ca2+, Mg2+) over monovalent cations (K+, Na+) by the clay minerals may explain the chemistry of both the unsaturated zone solutions and at the immediate water table.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79656995","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Standard approach for modeling and understanding the variability of statistical data or, generally, dependant data, is often based on the mean variance regression models. However, the assumptions employed on standardized residuals may be too restrictive, in particular, when the data follows heavy-tailed distribution with probably infinite variance. This paper considers the problem of nonparametric estimation of conditional scale function of time series, based on quantile regression methodology of Koenker and Bassett (1978). We use a flexible model introduced in Mwita (2003), that makes no moment assumptions, and discuss an estimate which we get by inverting a kernel estimate of the conditional distribution function. We finally prove the consistency and asymptotic normality for the estimate. Key word and phrases. Conditional quantile, kernel estimate, quantile autoregression, ARCH, QARCH, time series, consistency, asymptotic normality, value-at-risk.
{"title":"Conditional scale function estimate in the presence of unknown conditional quantile function","authors":"P. Mwita, R. Otieno","doi":"10.4314/AJST.V6I1.55165","DOIUrl":"https://doi.org/10.4314/AJST.V6I1.55165","url":null,"abstract":"Standard approach for modeling and understanding the variability of statistical data or, generally, dependant data, is often based on the mean variance regression models. However, the assumptions employed on standardized residuals may be too restrictive, in particular, when the data follows heavy-tailed distribution with probably infinite variance. This paper considers the problem of nonparametric estimation of conditional scale function of time series, based on quantile regression methodology of Koenker and Bassett (1978). We use a flexible model introduced in Mwita (2003), that makes no moment assumptions, and discuss an estimate which we get by inverting a kernel estimate of the conditional distribution function. We finally prove the consistency and asymptotic normality for the estimate. Key word and phrases. Conditional quantile, kernel estimate, quantile autoregression, ARCH, QARCH, time series, consistency, asymptotic normality, value-at-risk.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73667685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study we have addressed the NP-Hard problem of academic course timetabling. This is the problem of assigning resources such as lecturers, rooms and courses to a fixed time period normally a week, while satisfying a number of problem-specific constraints. This paper describes a Tabu Search algorithm that creates timetables by heuristically minimizing penalties over infeasibilities. The algorithm is developed with special focus on the University of Dar-assalaam and compares the results with a previous manually generated timetable. It has been found that, the Tabu Search technique gives better results given a careful selection of parameters.
{"title":"Tabu search heuristic for university course timetabling problem","authors":"A. Mushi","doi":"10.4314/AJST.V7I1.55191","DOIUrl":"https://doi.org/10.4314/AJST.V7I1.55191","url":null,"abstract":"In this study we have addressed the NP-Hard problem of academic course timetabling. This is the problem of assigning resources such as lecturers, rooms and courses to a fixed time period normally a week, while satisfying a number of problem-specific constraints. This paper describes a Tabu Search algorithm that creates timetables by heuristically minimizing penalties over infeasibilities. The algorithm is developed with special focus on the University of Dar-assalaam and compares the results with a previous manually generated timetable. It has been found that, the Tabu Search technique gives better results given a careful selection of parameters.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72669037","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
115 deblais de sondage et des logs electriques ont ete soumis aux analyses biostratigraphiques et paleoenvironnementales pour determiner la lithologie, l’âge, et l’environnement de depot des sediments provenant du puits Opolo-1 dans le Delta du Niger, Nigeria. Les resultats montre que du bas vers le haut de l’intervalle, les sediments sont des argiles noires qui passent progresssivement aux sables argileux et finallement au gres au sommet du puits. Les gres sont plus ou moins bien tries, anguleux a subanguleux, fins a grossiers. La presence de la pyrite diagenetique dans toute la section etudiee nous amenent a conclure que le processus de depot a eu lieu dans des conditions calmes et reductrices. 124 especes de foraminiferes comprenant 82 benthiques (66%) et 42 planctiques (34%) ont ete identifiees et utilisees pour la datation, la biozonation et l’interpretation paleoenvironnemental. L’âge du Miocene moyen au Pliocene inferieur est proposee. Sur la base du premier niveau d’apparition des foraminiferes planctiques diagnostiques, six biozones ont ete reconnues. Les paleoenvironnements de depots varient du neritique au bathyal et sont caracterises par la presence d’especes tel que Ammobacculites sp., Ammonia beccarii, Quinqueloculina lamarkiana dans les milieux neritiques et Bolivina scalprata miocenica, Cyclammina cancellata, et Heterolepa pseudoungeriana dans les zones bathyales.
{"title":"Biostratigraphie des foraminiferes et interpretation paleoenvironnementale du puits opolo- i dans le delta du Niger, Nigeria","authors":"J. M. Cheoh, Ce Bassey, C. M. Agyingi","doi":"10.4314/AJST.V6I2.55172","DOIUrl":"https://doi.org/10.4314/AJST.V6I2.55172","url":null,"abstract":"115 deblais de sondage et des logs electriques ont ete soumis aux analyses biostratigraphiques et paleoenvironnementales pour determiner la lithologie, l’âge, et l’environnement de depot des sediments provenant du puits Opolo-1 dans le Delta du Niger, Nigeria. Les resultats montre que du bas vers le haut de l’intervalle, les sediments sont des argiles noires qui passent progresssivement aux sables argileux et finallement au gres au sommet du puits. Les gres sont plus ou moins bien tries, anguleux a subanguleux, fins a grossiers. La presence de la pyrite diagenetique dans toute la section etudiee nous amenent a conclure que le processus de depot a eu lieu dans des conditions calmes et reductrices. 124 especes de foraminiferes comprenant 82 benthiques (66%) et 42 planctiques (34%) ont ete identifiees et utilisees pour la datation, la biozonation et l’interpretation paleoenvironnemental. L’âge du Miocene moyen au Pliocene inferieur est proposee. Sur la base du premier niveau d’apparition des foraminiferes planctiques diagnostiques, six biozones ont ete reconnues. Les paleoenvironnements de depots varient du neritique au bathyal et sont caracterises par la presence d’especes tel que Ammobacculites sp., Ammonia beccarii, Quinqueloculina lamarkiana dans les milieux neritiques et Bolivina scalprata miocenica, Cyclammina cancellata, et Heterolepa pseudoungeriana dans les zones bathyales.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"168 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76940063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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