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Page will reload when a filter is selected or excluded.- Brayton cycle 2 results 2
- "Optimal allocation of products to downstream locations is a major requirement for minimizing the distribution costs associated with supply chain systems. Unfortunately many supply chain managers rely on their intuition and feelings to make these allocation decisions. In this study a mathematical model was developed for minimizing the distribution cost in a multi-product 2-echleon supply chain system. The distribution system of a leading bottling plant in Nigeria was studied to understand the underlying supply chain system . Attempt was made to identify system parameters, variables, limitations, criteria so as to be able to define the distribution problem The interactions and flow of products in the system were identified and characterized as a 2 echelon supply chain system. Mathematical model of the system was developed. The problem model, a linear program formulation with three major constraints; demand, availability and company policy requirements was parameterised based on demand data product availability data, company policies and unit transportation costs to various downstream locations. The model was solved for a 12 product 8 destination case. It was observed that the model application produces 6% reduction in the distribution cost compared to the existing practice of the company. It is concluded that the model is effective to reduce or minimize distribution expenses for any multiproduct multiple destination system and fulfilling demand at various destinations. " 1 results 1
- Anaerobic digestion 1 results 1
- Biogas yield 1 results 1
- Biopulping 1 results 1
- Bottling Company 1 results 1
- Cu2ZnSnS4 1 results 1
- Distribution. 1 results 1
- Electronics 1 results 1
- Entropy generation 1 results 1
- Exchanger 1 results 1
- General 1 results 1
- Greenhouse gases emitted from burnt fossil fuels are major contributors to global warming which currently threatens existence of life. Hence, the global campaign for the replacement of fossil fuels with solar energy. The Cu2ZnSnS4 (CZTS) thin film has emerged as a promising material for photovoltaic absorption layer in the fabrication of solar cells. Various methods of deposition have been used to fabricate superstrate CZTS thin film solar cells. However, there is limited information on the use of sol-gel method which is known to perfectly control chemical composition for the fabrication of this type of solar cells. In this study, a superstrate structured CZTS thin film solar cell was fabricated using the sol-gel method and thereafter characterised. The possibility of using paper tape during the fabrication process instead of photomask which is not always readily available was also investigated. Superstrate structured CZTS thin film solar cells were fabricated using atmospheric pressure chemical vapour to deposit SnO2:F thin film (as window layer). Also, spin coating method was used to deposit CdS thin film (as buffer layer) from the sol-gel of cadmium acetate, 2-methoxy ethanol, thiourea and polyethylene glycol. Sol-gel sulphurising method was used to deposit Cu2ZnSnS4 thin film (as absorber layer) from CuCl2, ZnCl, SnCl2 and thiourea (as sulphur source). Layers of the film were masked using paper tape, optimised and characterised following standard procedures before being used in the fabrication of (SLG)/FTO (SnO2:F)/Ag/CdS/CZTS/Al solar cell. The deposited films were characterised using scanning electron microscope for surface morphology, Jandel universal four point probe for sheet resistance, MD-10 X-ray Diffractometer for crystallography and AvaSpec-2048 UV-VIS spectrophotometer for optical properties. The CZTS thin film solar cells of active area 2.25cm2 were examined for their efficiencies using the Newport solar simulator under irradiation of 100 mW/cm2. The mean of the efficiencies of CZTS solar cells from sol-gel method were compared with previous work on screen printing and doctor-blade methods. The SnO2:F thin film obtained had a transmittance of 80% in the UV-Visible region of the electromagnetic spectrum and a sheet resistance of 15 Ω/sq which is within acceptable values for a window layer. The calculated energy band gap of the CdS and CZTS films from the transmittance and reflectance data were 2.40 eV and 1.51 eV respectively. This value for CZTS is closest to near-optimal direct band gap value (1.50eV) when compared with those obtained via screen printing (1.40eV) and doctor blade (1.41eV) methods. The X-ray diffraction pattern of the CdS film exhibit hexagonal structure with (002) orientation while CZTS film had kesterite structure with (112) orientation. The absorption co-efficient of CZTS film in the visible region was 104 cm-1. The X-ray diffraction pattern showed sharp peaks whereas broadened peaks were observed in the X-ray diffraction pattern obtained via doctor blade method. The fabricated solar cells with buffer layer thicknesses of 40 nm and 60 nm had efficiencies of 0.28 0.01% and 0.13 0.01% respectively when compared with screen printing (0.53%) and doctor-blade (0.55%). Superstrate Cu2ZnSnS4 solar cells have been successfully fabricated using sol-gel spin coating method and paper tape in lieu of photomask 1 results 1
- Hydrolytic enzymes 1 results 1
- In this work, three variants of the Brayton cycle incorporating concentrated solar technologies and dual regenerative systems are modeled. The first variant employs reheat, intercooling, and regeneration, the second applies intercooling and regeneration while the third case involves regeneration only. With the application of the entropy generation method and particle swarm algorithm (PSA), processes with the largest irreversibilities are noted, minimized and the geometric parameters of participating components are optimized. Results show that irreversibilities occurring in the systems were largely due to finite temperature differences within components. In all cases, the solar receiver and intercooler are the dominant and modest sources of entropy generation respectively. The regenerative system entropy generation is highest in the first case while decreasing in the second and third cases respectively. An improvement in the exergy availability was observed in the first case, as the first and second law efficiency peaks at 44.9% and 59.68% respectively. Though, with a lower second law efficiency than the former, its percentage network output is equal to the first case at 43%. The aspect ratio, hydraulic diameter, and length of the receiver were observed to vary to enhance greater heat capture and increase the turbine inlet temperature (TIT). The high temperature (HT) regenerator had its geometric properties of a higher magnitude than the low temperature (LT) system as the waste heat recovery is aided by an enhanced heat transfer surface area. In comparison with the single regeneration system, the network output of the dual model was about 33.5% with a significant reduction in the entropy generated, creating a trade-off between operating the system for more power or less generation of irreversibilities. 1 results 1
- Irreversibility 1 results 1
- Multi-feedstock 1 results 1
- Native fungi 1 results 1
- Optimisation 1 results 1
- Optimisation. 1 results 1
- Parallel plate heat exchanger 1 results 1
- Particle swarm optimization 1 results 1
- Photomask 1 results 1
- Pulping industry is both labour and energy intensive but in Nigeria, electricity supply is unstable. This has contributed to the near collapse of the Nigerian paper and pulp industry despite the rich forest resources in southwestern Nigeria. Use of alternative energy sources such as electricity generating sets further increases production cost. It therefore, becomes pertinent to seek alternative approach aimed at reducing mechanical pulping duration and improving pulp characteristics. The aim of the study was to characterise major hydrolytic enzymes of native fungi from selected wood samples and evaluate their biopulping potential. Chipped samples of three local woods (Anogeissus leiocarpus, Gmelina arborea and Terminalia superba) from Ekiti, Lagos, Ogun, Ondo, Osun and Oyo States were made to undergo spontaneous degradation. Thereafter, fungi were isolated, identified and screened for cellulase and hemicellulase production. Isolates selected based on maximal enzyme activities were used to produce cellulases (glucanase and glucosidase) and hemicellulases (mannanase and xylanase) with the chips as substrates. Kinetic, molecular and biochemical properties of partially purified hemicellulases were determined and optimised using standard methods. Chipped wood samples were subjected to treatments with fungal isolates singly and in combination for six weeks. Treated wood samples and pulp were evaluated fortnightly for changes in cellulose, hemicellulose, lignin and ash contents, tensile strength, fibre length and strength. Data were analysed using descriptive statistics and ANOVA at p = 0.05. Five hundred and twenty-six fungal isolates were obtained and identified as Aspergillus flavus(13), Aspergillus niger(125), Rhizopus spp(79). Lasiodiplodia theobromae(10), Penicillium purpurogenum(25), Fusarium chlamydosporium(37), Fusarium oxysporum(30), Fusarium compactum(25), Trichoderma harzianum(75), Trichoderma reesei(88) and Emericella nidulans(19). Aspergillus niger, F. compactum, T. harzianum and T. reesei were selected for enzyme production. Highest production of cellulase was 12.72U/gm±0.11 on A. leiocarpus by T. reesei. Best producer of mannanase was A. niger with 15.50U/gm±0.01 on G. arborea while highest xylanase production of 28.93U/gm±0.12 was by F. compactum on A. leiocarpus. Kinetic properties of xylanase was Vmax 1.402U/min/ml and Km 1.804U/ml with molecular weight of about 90kDa and that of mannanase was Vmax 0.754U/min/ml, Km 1.364U/ml and molecular weight was between 53 and 65kDa. Optimum xylanase activity was at 55oC and pH 5.5 while mannanase was at 30oC and pH 5.5. There was significant reduction in hemicellulose (45-27%) and lignin (20-15%) in treated wood compared to untreated samples. Gmelina arborea singly treated with F. compactum gave best result: cellulose, hemicellulose, lignin and ash were reduced by 14.1, 18.9, 4.1 and 4.7 % respectively; while tensile strength, fibre length and strength improved respectively by 6.4, 4.3 and 6.5 %. These conformed to Technical Association of Paper and Pulp Industries standard. Treatment of T. superba with combination of F. compactum and T. harzianum however, reduced cellulose, hemicellulose, lignin and ash by 20.7, 39.4, 11.9 and 10.6 % respectively, giving a better result than that obtained with single treatment. Fungal enzyme treated wood samples attained pulp characteristics that met required biopulping standard. Thus, native fungi may be employed for biopulping of common woods in Nigerian paper and pulp industries. 1 results 1
- Renewable energy 1 results 1
- Second law analysis 1 results 1
- Solar cells 1 results 1
- Spiral plate heat 1 results 1
- Superstrate thin film 1 results 1
- Supply chain, 1 results 1
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