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Page will reload when a filter is selected or excluded.- Absorption cooling- Systems 1 results 1
- Absorption refrigeration systems are generally characterized by low Coefficient of Performance (COP). Absorption enhancement is an effective way of improving the COP of refrigeration systems. Literature is sparse on the use of magnetic field for the enhancement of absorption refrigeration systems despite its cheapness and environmental friendliness as compared with other enhancement methods. Although the method has recently been employed on ammonia solution, its influence on lithium bromide (LiBr) and lithium chloride (LiCl) solutions is yet to be fully studied. In this study a numerical model for the magnetic field enhancement of the absorption cooling-system using LiBr and LiCl solutions was developed and evaluated. The flow within the film thickness to the absorber wall was considered as a two-dimensional steady laminar flow. A Finite Difference model was developed based on conservation of mass, momentum, energy equations and mass transport relationship. The model was validated using data from the literature on ammonia solution. Standard parameters including absorber wall length (1 m), film thickness (10-3 m), magnetic field vacuum permeability (1.257 x 10-6 kgmA-2s2), magnetic mass susceptibilities and magnetic induction intensities were used for LiBr and LiCl solutions' modeling. Changes in their concentrations, both in the direction of falling film and across its thickness, were investigated. Data were analysed using descriptive statistics and Student's t-test (p=0.05). The concentration distribution for ammonia solution within the film thickness was not significantly different from results in the literature. For the magnetic induction range of 0.0 and 3.0 Tesla, the concentration distribution of LiBr solution in the direction of falling film was between 54.9% and 60.0%, while that of LiCl solution ranged between 39.9% - 45.0%. Meanwhile, across the film thickness and for the same range of magnetic induction of 0.0 and 3.0 Tesla, the concentration distribution for LiBr solution was between 0.0 and 0.19 and those of LiCl solution were between 0.0 and 0.13. The concentration of LiBr solution increased from 0.0 to 4.7 and 0.0 to 21.7 when magnetic induction was increased from 0.0 to 1.4 and 0.0 to 3.0 Tesla, respectively. Similarly for LiCl solution, increased values of 0.0 to 3.3 and 0.0 to 15.5 were obtained when magnetic induction was increased from 0.0 to 1.4 and 0.0 to 3.0 Tesla, respectively. In both cases, it implies higher cooling effect. Relative to 0.0 Tesla, the COP of LiBr and LiCl solutions absorption refrigeration systems was increased by 0.1% when magnetic induction was 1.4 Tesla, while increment of 0.3% and 0.2% respectively were obtained when magnetic induction was 3.0 Tesla. The percentage increments in COP of LiBr solution were not significantly different from that of the LiCl solution. Magnetic field enhanced the absorption performance in the lithium bromide and lithium chloride solutions; hence can be used in typical absorption refrigeration systems. 1 results 1
- Aerodynamic properties 1 results 1
- Africa 1 results 1
- Background: Laboratory-based studies of neurological disease patterns and mechanisms are sparse in sub-Saharan Africa. However, availability of human brain tissue resource depends on willingness towards brain donation. This study evaluated the level of willingness among outpatient clinic attendees in a Nigerian teaching hospital. Methods: Under the auspices of the IBADAN Brain Bank Project, a 43—itemsemi-structured interviewer—administered questionnaire was designed to evaluate knowledge, attitude, and beliefs of individuals attending Neurology, Psychiatry and Geriatrics Outpatient clinics regarding willingness to donate brain for research. Association between participants characteristics and willingness towards brain donation was investigated using logistic regression models. Analysis was conducted using Stata SE version 12.0. Results: A total of 412 participants were interviewed. Their mean age was 46.3 (16.1) years. 229 (55.6%) were females and 92.5% had at least 6 years of formal education. Overall, 109 (26.7%) were willing to donate brains for research. In analyses adjusting for educational status, religion, ethnicity, marital status and family setting, male sex showed independent association with willingness towards brain donation OR (95% CI) 1.7 (1.08–2.69), p = 0.023. Participants suggested public engagement and education through mass media (including social media) and involvement of religious and community leaders as important interventions to improve awareness and willingness towards brain donation. Conclusion: The survey revealed low willingness among outpatient clinic attendees to donate brain for research, although men were more inclined to donate. It is imperative to institute public engagement and educational interventions in order to improve consent for brain donation for research. 1 results 1
- Background: Traumatic Spinal Cord Injury (TSCI) is a costly condition in human and economic terms. Yet, studies on direct cost of treatment for TSCI in resource-constraint countries are sparse. Objective: To estimate the direct cost of treatment for patients with TSCI at the University College Hospital (UCH), Ibadan, Nigeria using an incidence-based costing approach. Methods: All new cases of TSCI admitted in the hospital from January, 2009 to December, 2013 were identified and reviewed. Direct costs of in-patient and out-patient treatments over the first year of injury were estimated. Results: 114 individuals with TSCI (73 males; 41 females) were admitted and discharged home alive from the hospital. The largest cost driver to the patients and the National Health Insurance Scheme was cost of consultations by neurosurgeons which constituted about a third (34.4%) of the total costs of treatment. Less than a fourth (24.2%) of the total cost of in-patient treatment was spent on therapeutic interventions (surgery, drugs and physiotherapy). There was a significant relationship between the direct cost of treatment and each of the severity of traumatic spinal cord injury and length of hospital stay (p = 0.01). Level of injury was not significantly associated with direct cost of treatment (p=0.89). Conclusion: Direct cost of treatment for individuals with TSCI in Ibadan, Nigeria is substantial. This high cost underscores the need for novel service models with potential for minimizing cost for patients with TSCI in Nigeria. 1 results 1
- Cancer risk 1 results 1
- Communications 1 results 1
- Cost of Treatment 1 results 1
- Cowpea 1 results 1
- General 1 results 1
- Ingestion effective dose 1 results 1
- Ionizing radiations resulting from either natural or artificial radioactivity are useful but associated with them are health risks which increase with exposure. The natural radioactivity levels in soils of some locations in Jos and Abeokuta are significantly higher than the world average. Enhanced internal and external radiation exposures to man may result from physical presence in, and ingestion of food items grown in these areas. Scientific data are sparse on the radionuclide contents in food crops, farm soils and their radiological implications on the population. Therefore the aim of this study was to determine the radioactivity levels of 40K, 226Ra and 232Th in food crops and farm soils, and associated cancer risks in the population in the areas. A total of 243 food crop samples from 19 commonly grown types including acha, cowpea, cassava, cocoyam, Guinea corn, maize and yam; and 106 soils samples were randomly collected from 40 farm lands, 23 in Jos and 17 in Abeokuta, selected at random. The samples were air dried to constant mass, pulverized, sieved to pass 2mm mesh-size and sealed for 4 weeks to attain secular equilibrium. The activity concentration of the radionuclides were determined by counting each sample for 10 hours using a gamma-ray spectrometer comprising 76mm x 76mm NaI(TI) detector coupled to a multichannel analyzer. The effective dose rates due to ingestion of the food crops and outdoor effective dose rates due to farm soils were evaluated using the calculated activity concentrations and food consumption rates from Federal Office of Statistics, Nigeria. The risk of incurring cancer from radiation exposure were evaluated using carcinogenicity radionuclide slope factors by United States Environmental Protection Agency and the linear non-threshold radiation risk model, and compared with the International Commission on Radiological Protection (ICRP) recommended limits. Data were analyzed using descriptive statistics. The concentration of 40K, 226Ra and 232Th in food crops in Jos ranged from 8.7-1406.1, 2.1-85.5 and 2.6-89.8 Bqkg-1 respectively; whereas in Abeokuta the range was 38.2-1648.3, 2.1-81.1 and 2.6-48.3 Bqkg-1 respectively. The concentration of 40K, 226Ra and 232Th in farm soils were respectively 698.0±416.0; 143.1±80.8 and 287.3±306.3 in Jos and 411.0±341.0; 65.0±29.0 and 184.0±205.0Bqkg-1 in Abeokuta. The radioactivity levels were higher in Jos than Abeokuta. The tin mining in Jos might be the principal differential factor for its elevated radioactivity compared to Abeokuta. The annual average effective doses due to food ingestion in Jos was 0.20.01Sv (cowpea), 1852.0±43.1μSv (yam); in Abeokuta 58.7±15.7μSv (cocoyam) and 1064.6±32.2μSv (cassava). The average annual outdoor effective doses from farm soils were 0.430.32mSv for Jos and 0.210.18mSv for Abeokuta. The cancer risks due to farm soils and food ingestion were 1.42 x 10-2 and 8.57x10-3 for Jos and Abeokuta respectively. The effective doses were below the ICRP recommended limit of 1mSv and the cancer risks were slightly higher than the ICRP value of 1.0 x10-3. Cassava and yam had high radioactivity compared to other food crops. Radiological cancer risk among the population was high. The quantity of cassava and yam consumed from the areas should be reduced. 1 results 1
- LMIC 1 results 1
- Magnetic field 1 results 1
- Nigeria 1 results 1
- Pneumatic cleaning 1 results 1
- Possible world semantics 1 results 1
- Quantified modal logic 1 results 1
- Radioactivity 1 results 1
- Refrigeration 1 results 1
- Separation efficiency 1 results 1
- Spatial qualification model 1 results 1
- Spatial qualification problem, an aspect of spatial reasoning, is concerned with the impossibility of knowing an agent‟s presence at a specific location and time. An agent‟s location determines its ability to carry out an action given its known spatial antecedents. There are sparse works on the formalisation of this problem. Qualitative reasoning approach is the most widely used approach for spatial reasoning due to its ability to reason with incomplete knowledge or reduced data set. This approach has been applied to spatial concepts, such as, shapes, sizes, distance and orientation but not spatial qualification. Therefore, this work was aimed at formalising a logical theory for reasoning about the spatial qualification of an agent to carry out an action based on prior knowledge using qualitative reasoning approach. The notions of persistence, discretisation and commutative distance coverage were used as parameters in formalising the concept of spatial qualification. The axioms and derivation rules for the theory were formally represented using quantified modal logic. The formalised theory was compared with standardised systems of axioms: S4 (containing Kripke‟s minimal system K, axioms T and 4) and S5 (containing K,T,4 and axiom B). The characteristics of the domain of the formalised theory were compared with Barcan‟s axioms, and its semantics were described using Kripke‟s Possible World Semantics (PWS) with constant domain across worlds. A proof system for reasoning with the formalised theory was developed using analytical tableau method. The theory was applied to an agent‟s local distribution planning task with set deadline. Cases with known departure time and routes were considered to determine the possibility of an agent‟s presence at a location. From the formalisation, a body of axioms named Spatial Qualification Model (SQM) was obtained. The axioms showed the presence log and reachability of locations as determinants for agent‟s spatial presence. The properties exhibited by the formalised UNIVERSITY OF IBADAN LIBRARY xvii model when examined in light of S4 and S5 systems of axioms were KP1, KP2 (equivalent to axiom K), TP and 4P (equivalent to axioms T and 4 respectively) in an S4 system. The SQM therefore demonstrated the characteristics of an S4 system of axioms but fell short of being an S5 system. Barcan‟s axiom held, confirming constant domain across possible worlds in the formalised model. Explicating the axioms in the SQM using PWS enabled the understanding of tableau proof rules. Through closed tableaux, the SQM was demonstrably semi-decidable in the sense that the possibility of an agent‟s presence at a certain location and time was only provable in the affirmative, while its negation was not. Depending on the route, the application of SQM to the product distribution planning domain resulted in agent‟s feasible availability times, within or outside the set deadline to assess the agent‟s spatial qualification in agreement with possible cases in the planning task. The spatial qualification model specified the spatial presence log and reachability axioms required for reasoning about an agent‟s spatial presence. The model successfully assessed plans of product distribution task from one location to the other for vans‟ availability. Keywords: Spatial qualification model, Quantified modal logic, Tableau proof, Possible world semantics. Word count: 497 1 results 1
- Tableau proof 1 results 1
- The presence of impurities in cowpea affects its economic value as well as industrial and domestic utilisation. This problem has persisted despite the use of various manual and mechanical cleaning methods. There exists a need to improve the efficiencies of existing cowpea cleaning devices. Literature is sparse on modelling of pneumatic separation of cowpea. This study was therefore designed to develop and validate a mathematical model for the efficient separation of impurities from cowpea in a pneumatic cleaner. Some physical and aerodynamic properties of four cultivars of cowpea (Ife 98-12, IT90K-277-2, Ife Brown and Drum) and impurities (chaff, insect infested grains and immature grains) were determined at harvesting and at storage moisture contents range (9-22% dry basis) using standard methods. A two-dimensional mathematical model for separating cowpea and impurities in a vertical flow airstream was developed using the force and acceleration components of each particle in the horizontal and vertical directions. The resultant equations were solved numerically for displacements using a proprietary software at injection angles of 15, 30, 45 and 60o which are greater than the coefficient of friction for cowpea on mild steel and air velocities of 4.0, 6.0, and 8.0 m/s which are also greater than the impurities’ terminal velocities. The displacements were used to predict the trajectories of cowpea, impurities and their separation. The model was validated using a pneumatic cleaner and the separation efficiencies were evaluated at the angles of injection and air velocities. A paired t-test was used to compare the experimental and predicted efficiencies. The axial dimensions, geometric mean diameter, thousand grain mass, projected area and terminal velocity of the cultivars ranged from 5.0-10.3 mm, 6.1-7.0 mm, 147.5-252.8 g, 28.0-43.6 mm2 and 13.4-14.5 m/s respectively. The mass and terminal velocity of the impurities ranged from 8.2 x 10-2-15.0 x 10-2 g and 1.5-3.5 m/s respectively. Vertical displacements of the cultivars below the point of injection ranged from 3.9-4.8 m. The vertical displacements of the impurities above and below points of injection varied from 3.4-72.1 m and 0.70-3.2 m respectively. The predicted separation distances between cultivars and impurities ranged from 5.0 x 10-2 - 897.0 x 10-2 m. The predicted separation efficiency ranged from 30.0-45.8%, 59.3-70.6%, 76.5-83.9% and 55.2-61.6%, 77.0-79.0%, 85.0-86.9% at 4.0, 6.0, and 8.0 m/s for injection angles of 15-30o and 45-60o respectively. Separation efficiencies of the machine ranged from 27.7- 44.6%, 61.4-71.9% and 76.6-80.4% for angles of 15-30o at 4.0, 6.0, and 8.0 m/s respectively. For angles of 45-60o, it ranged from 59.2-60.9%, 75.4-76.0% and 87.2-88.8% at 4.0, 6.0, and 8.0 m/s respectively. The model predicted significantly (p≤ 0.05) the separation efficiency within the experimental range. A mathematical model for the separation of cowpea and impurities in a pneumatic cleaner was developed. It was established that separation of impurities from cowpea was best at 45o angle of injection at 4.0-6.0 m/s. Therefore, it is recommended that the hopper should be inclined to the airstream at this angle. 1 results 1
- Thin-liquid Falling-film 1 results 1
- Willingness 1 results 1
- brain Banking 1 results 1
- brain donation 1 results 1
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