Biopreservative activity of lactic acid bacteria on suya produced from poultry meat

The influence of lactic acid bacteria (LAB) isolated from poultry meat on the attributes of suya was investigated. Lactobacillus plantarum with the highest frequency of occurrence (90%) produced the highest amount of lactic acid (16.2 g/l) and inhibited all the indicator organisms with the exception of Candida albicans and Proteus vulgaris. Consequently, L. plantarum was chosen as the starter culture to inoculate pieces of poultry meat before (CB) and after (CA) grilling for suya production. Relatively lowmicrobial counts (log cfu/g) of coliform (8.23), Staphylococcus (4.83), LAB (8.1) and yeast/mould (5.63) were observed for CA samples after six days of storage. Grilling at 80oC for 30 min gave the best suya attributes with crude protein content of 33.45%. The best packaging material was polyphenylchloride as compared to aluminum foil and newsprint

Design development of brushless doubly fed machines

Thesis (PhD)--Stellenbosch University, 2022.ENGLISH ABSTRACT: Doubly fed induction generators (DFIGs) are the most widely used generators in large wind turbines, because of their cheap constructions, smaller converter sizes, and wide speed range. However, DFIGs have well known reliability issues stemming from their slip ring and brush failures. This is particularly problematic in remote areas like offshore wind sites. Currently, the operational and maintenance costs of DFIG based wind turbines are the highest among commonly used offshore wind topologies, due to the slip ring and brush failures. It should be noted that offshore wind power is getting increasing attention, and significant increases in offshore wind installations are projected in the coming years. The use of brushless doubly fed (induction) machines (BDFMs) has been proposed as an alternative to DFIGs, especially in remote areas like offshore sites, as they do not have slip rings and brushes. BDFMs, which are typically medium speed machines, also have better low voltage ride through characteristics compared to DFIGs, which could help reduce cost and complexity of their drivetrains. However, BDFMs have a more complex structure to DFIGs, with considerably lower power densities. Also, BDFMs have higher total harmonic distortions and vibrations compared to DFIGs. With their development still being at experimental stages, there is no well-defined way to design BDFMs, with the design of certain parts still debated. In this project, the start to finish design process of BDFMs is investigated. The thought process behind certain decisions like the placement of the stator windings are highlighted. The design of a suitable rotor topology per BDFM application isresearched. The rotor design is conducted with power density and harmonics/vibrations considered. A proper method for BDFM design evaluation is demonstrated especially when considering grid complaint operations. This evaluation method is compared with evaluation methods com monly used in available literature to demonstrate its suitability. With proper evaluation deter mined, the optimization of BDFM designs is investigated using different models. A coupled circuit model is developed for use in the rotor design. Results from finite element analysis models are used to develop response surface approximations which are coupled with a genetic algorithm for power density optimizations. There are established values of certain input parameters such as the electric and magnetic loadings in DFIG design. This is however not the case with BDFMs. Consequently, in this project, practical values of these parameters are researched for different BDFM power ratings. The disparities in power density between BDFMs with different pole pair combinations and DFIGs at corresponding rated speeds across different power ratings are mapped out. These disparities in power density are used to recommend the best performing pole pair combinations at different power ratings.AFRIKAANSE OPSOMMING: Dubbel gevoerde induksie generators (DGIGs) word gereeld in groot wind turbines gebruik omdat dit goedkoop is om aan mekaar te sit, kleiner omskakelaar groottes het, en ‘n wye spoed verskeidenheid het. Ten spyte hiervan het DGIGs betroubaarheid probleme wat veroorsaak word deur die gly ring en borsel mislukkings. Dit is veral ‘n probleem in afgesonderde areas soos buitelandse wind plase. As gevolg hiervan is DGIG gebaseerde wind turbines se kostes die hoogste onder algemeen gebruikte buitelandse wind tipologiee.¨ Dit is belangrik om in ag te neem dat daar meer aandag aan buitelandse wind krag gegee word en dus word daar ‘n beduidende toename in buitelandse wind installasies vir die komende jare geprojekteer. Die gebruik van borsellose dubbel gevoerde (induksie) masjiene (BDGMe) is al as ‘n alterna tiewe opsie vir DGIGs voorgestel, veral vir afgesonderde areas omdat hulle nie gly ringe of borsels het nie. BDGMe, wat tipies medium spoed masjiene is, het ook beter lae spanning rit deur eienskappe as DGIGs wat kan help om die kostes en kompleksiteit van die dryf stelsels te verminder. Daar moet egter in ag geneem word dat BDGMe ‘n baie meer komplekse struktuur het met laer krag digthede. BDGMe het ook hoer¨ totale harmoniee¨ versteurings en vibrasies wanneer dit met DGIGs vergelyk word. Met die masjiene se ontwikkeling wat nog in ekspe rimentele fases is, is daar nog nie ‘n goed-gedefinieerde manier om BDGMe te ontwerp nie, veral omdat sekere dele se ontwerpe nog gedebatteer word. In die projek word die proses van BDGMe ontwerp van begin tot einde ondersoek. Die proses van sekere besluite wat gemaak is, soos die plasing van die stator windings, word uitgelig. Die ontwerp van ‘n toepaslike rotor topologie per BDGM toepassing word ook in die studie nagevors. Die rotor ontwerp is met die inagneming van krag digtheid en harmoniee/vibrasies ¨ uitgevoer. ‘n Gepaste metode vir die evaluering van BDGM ontwerp is gedemonstreer, veral wanneer krag-netwerk voldoende bedrywighede in ag geneem word. Die evaluasie metode is met ander metodes wat algemeen in beskikbare literatuur gebruik word vergelyk om die geskiktheid daarvan te demonstreer. Met die gepaste evaluasie wat bepaal is, is die optimalisering van BDGM ontwerpe ondersoek deur gebruik te maak van verskeie modelle. ‘n Gekoppelde baan model is vir die gebruik in rotor ontwerp ontwikkel. Resultate van beperkte element analise modelle is gebruik om reaksie oppervlak benaderings te ontwerp wat aan die genetiese algoritme vir krag digtheid optimaliserings ontwikkel is. Daar is bepaalde waardes van sekere inset parameters, soos die elektriese en magnetiese ladings in die DGIG ontwerp. Dit is egter nie die geval vir BDGMe nie. As gevolg hiervan word daar in die projek praktiese waardes van die parameters vir verskillende BDGM krag grade rings nagevors. Die ongelykhede in krag digtheid tussen BDGMe met verskillende pool paring kombinasies en DGIGs teen ooreenstemmende gegradeerde spoed oor verskillende krag graderings is uiteengesit. Die ongelykhede is gebruik om die beste pool paring kombinasies teen verskillende spoed graderings voor te stel.Doctora

Evaluation of Indigenous Poultry Improvement Project in Irepodun Local Government Area of Kwara State

The study assessed an indigenous poultry improvement project carried out at Irepodun LGA of Kwara State. The focal objective of the project was to facilitate traditional backyard poultry development through improved chicks’ survivability. Ten (10) indigenous backyard poultry farmers were selected based on willingness to participate in the project from Rore Village of Irepodun LGA and were trained on the rudiments of the projects and improved poultry management practices. Baseline data were collected at the onset of the project on the level of chick survivability and other parameters. Cages, feeds, medication were supplied while each farmer was to provide five laying hens. Upon hatching, the chicks were reared in cages for six weeks without the mother hen. The project was found to yield 70 – 90% chick survival up to 6 weeks of age. Bird mortality was noticed to decline considerably after 6 weeks of age when the birds are turned to scavengers. It is concluded that the innovation is result-oriented and therefore recommended for extension dissemination and farmers` trials

Design of a rotor-tied doubly fed induction generator

Thesis (MEng)--Stellenbosch University, 2017.ENGLISH ABSTRACT: The severe e ects of climate change has seen a global push towards an increase in the use of renewable energy sources. Wind energy is a major renewable energy source and its usage in electricity generation is steadily rising. The doubly fed induction generator (DFIG) is the most commonly used generator in wind turbines due to its wide speed range of operation and easy power factor control implementation. DFIGs also use fractionally rated power converters which have lower converter losses compared to fully rated converters in induction and synchronous generators. Recently, a new DFIG topology (the rotor-tied DFIG) has been proposed. In this topology, the DFIG's rotor is connected to the grid and the stator to fractionally rated power converters. This topology has been shown to lead to higher efficiency as the higher frequency (grid frequency) is on the rotor core, which is typically smaller than the stator core, thus lower core losses. It was also suggested that designing DFIGs in this topology could lead to higher power densities. The topology requires no extra complexity in operations as a similar control system used with a conventional DFIG can be used. The steady state operation of the rotor-tied DFIG is first discussed and a new method of calculating slip for this topology is given. The proportions of the rotor and stator power to the input mechanical power to the generator at different slip values are illustrated. The transformer model equivalent circuit of rotor-tied DFIGs is also described. The purpose of this study is to design and optimize a low power rotor-tied DFIG. The design process is presented in a sequential manner from the calculation of the rotor size, to the rotor and stator winding parameters, then the slot and core dimensions. The obtained model is then evaluated with infinite element analysis (FEA) specific for rotor-tied DFIGs. The FEA is used to evaluate the power density, power factor and efficiency. The harmonic content in the model is also assessed. The design is then optimized to increase the power density and lower the harmonic content. A 5.5 kW rotor-tied DFIG is designed and its performance is evaluated using FEA. The optimization is executed using a response surface approximation of the FEA model with a genetic algorithm and this significantly reduces optimization time. The design of experiments for the response surface approximation is based on a combination of the latin hypercube sampling and composite sampling methods. Finally, a prototype is constructed and tested in a DFIG standalone mode. The tests are conducted in the sub-synchronous, synchronous, and super-synchronous regions of operation. The stator is excited with DC at synchronous speed, and slip frequency AC by the use of an AC drive at other speeds. The rotor is connected to a resistive load in all the tests. Tests results show that the prototype's efficiencies at synchronous and sub-synchronous speeds, for the rated stator current, are similar. The efficiencies at super-synchronous speeds are however lower with the same rated stator current due to the power rating of the AC drive used to excite the stator.AFRIKAANSE OPSOMMING: Die ernstige gevolge van klimaatsverandering het tot 'n globale toename in die gebruik van hernubare energiebronne gelei. Windenergie vorm 'n belangrike deel van die energiebronne en die gebruik van wind vir kragopwekking styg aanhoudend. Die dubbel-gevoerde induksie generator (DFIG) is die mees algemeen gebruikte generator in wind turbines weens sy wye omvang van spoed werking en eenvoudige implementering van arbeidsfaktor beheer. DFIGs gebruik ook laer kapasiteits omsetters in vergelyking met gewone induksie en sinchrone generators. Onlangs is 'n nuwe DFIG topologie (rotorgebonde DFIG) voorgestel. In die topologie word die masjien se rotor aan die netwerk gekoppel en die stator aan lae kapasitiet omsetters. Dit is bewys dat die topologie tot 'n hoër masjien effektiwiteit lei, omdat die hoër frekwensie op die rotor is. Dit lei tot minder kernverliese, weens die feit dat die rotor kleiner is as die stator. Dit is ook voorgestel dat DFIGs wat so ontwerp word, tot hoër drywingsdigthede kan lei. Die bedryf van 'n rotorgebonde DFIG vereis ook nie ekstra kompleksitiet nie, aangesien konvensionele DFIG beheerstelsels toegepas kan word. Die bestendige toestand werking van die rotorgebonde DFIG word bespreek, waarna 'n nuwe metode vir die berekening van die glip vir die topologie gegee word. Die verhouding tussen die rotor en stator drywing en die megansiese intree drywing by verskillende glip waardes word geïllustreer. Die ekwivalente transformator model van die rotorgebonde DFIG word ook beskryf. Die doel van die navorsing is om 'n lae drywing rotorgebonde DFIG te ontwerp en te optimeer. Die ontwerp proses word op 'n opeenvolgende wyse aangebied, vanaf die berekening van die rotor grootte, die rotor- en statorwikkelingsparameters en uiteindelik die gleuf en kern dimensies. Die voorgestelde model word dan met behulp van eindige element analise (EEA) geëvalueer. Die eindige element analise word gebruik om die drywingsdigtheid, arbeidsfaktor en effektiwiteit te evalueer. Die harmoniese inhoud in die model word ook geassesseer. Die ontwerp word dan geoptimeer om die drywingsdigtheid te verhoog en die harmoniese inhoud te verlaag. 'n 5.5 kW rotorgebonde DFIG is ontwerp en die prestasie word geëvalueer met behulp van die EEA program. Die optimeering geskied met behulp van 'n generiese oppervlak reaksie benadering algoritme. Die metode verminder die optimeeringstyd aansienlik. Die ontwerp van die oppervlak reaksie benadering is 'n kombinasie van die latyn hiperkubus en saamgestelde monsternemingsmetodes. Ten slotte word 'n prototipe van die rotorgebonde DFIG gebou en getoets in 'n alleenstaande modus. Die toetse word uitgevoer vir die sub-sinchroon, sinchroon en supersinchroon bedryfstoestande. Die stator is opgewek met 'n GS-bron by sinchroon spoed en met glip frekwensie WS, by die ander bedryfstoestande. Die rotor is aan 'n weerstandslas gekoppel vir al die toetse. Die toetsresultate toon dat die prototipe se effektiwiteit by sub-sinchroon en sinchroon spoed vir ken stator stroom, is soortgelyk. Die effektiwiteit by super-sinchroon is egter laer as gevolg van die kendrywing van die WS omsetter wat gebruik is om die stator op te wek

Towards an innovation system in the traditional sector: The case of the Nigerian Cocoa industry

Presented at the GLOBELICS 6th International Conference 2008 22-24 September, Mexico City, Mexico.In recent years the revitalization of the Nigerian cocoa industry through a cocoa re-birth initiative has been a major focus of the Nigerian government. By applying the analytical framework of the agricultural system of innovation this paper traces the process of valueaddition in the cocoa agro-industrial system, examines the impact of the Nigerian cocoa re-birth initiative and makes suggestions that are critical for strengthening the innovation system in a traditional sector. The study demonstrated that though an innovation system in the cocoa industry is far from being realized, the policy intervention of the cocoa rebirth initiative can be potent as an instrument of innovation. Towards this end, the findings suggest that policy emphasis should aim at organizing the cocoa re-birth initiative as an innovation focused programme that enables interactive learning among actors in cocoa research, production and industrial processing

Economic evaluation of a locally fabricated extraction machine for a cottage cashew juice factory.

The need for local utilisation of agricultural procedure cannot be over-emphasised. Agricultural commodities are shifting from exploitation in their primary to processed forms. Cashew apple, a product of the fruit of cashew tree and a by-product of cashew nut harvest, is presently under-utilised in Nigeria. There is so much wastage of this fresh apple on farms since a negligible portion is consumed by the harvesters. Work has been on for some time now at CRIN to harness this wastage into commercially viable human foods or food ingredients. Much progress has been made to-date on the production of juice from the apple. This study assesses the cottage utilisation of the apple using a locally fabricated extraction machine. The economic analysis of the investment indicated that it is highly profitable with a profitability of 66.19% and a net present value of N453, 283.21(US$4533) over three years, even under a short cashew harvesting period of three months. From these results, it was recommended that cashew farmer groups and co-operatives should be supported through credit facilities under the small-scale enterprise scheme to adopt this technology

Kola-pod husk as a partial substitute for maize in layers mash

No Abstract

A Review of the Advancements in the Design of Brushless Doubly Fed Machines

Research interest on brushless doubly fed induction machines (BDFMs) is increasing, as they offer higher reliability compared to doubly fed induction generators (DFIGs) in wind turbines. At the moment, BDFMs do not have a definitive structure nor design process, as literature is rife with different approaches to designing BDFMs. In this paper, a comprehensive review of the design of BDFMs from available literature is conducted. The evolution of cascade induction machine systems to contemporary BDFMs is first illustrated. Pioneering research work in the evolution which have influences on modern BDFM designs are highlighted. Relevant research on different aspects of present day BDFM design are then discussed. BDFM design and optimization methodologies applied in available literature are also explored

Partial Placement of Maize with Cocoa Husks Meals in Layers Mash: An on- farm Experience.

The partial replacement value of cocoa husk meals for maize in laying hen diets were assessed under an on-farm condition, Urea-treated and untreated cocoa husk meals were each incorporated into the farmer's layer mash (FLM) to replace 25% of the maize portion. FLM contained 40% maize. Six groups of 15 laying hens which were in the fifth month of lay were randomly allotted to the 3 dietary treatments including the control (FLM), cocoa husk-based mash (CHM) and urea-treated cocoa husk-based mash (UCHM). The diets were fed for 12 weeks. Egg product ion and egg mass were higher (p0.05) by dietary treatments. Feed cost was 9% lower on the test diets relative to FLM while feed cost/kg egg was 18% and 13% lower respectively on CHM and UCHM. These results indicate that cocoa husk meal could replace maize up to 25% in layers mash with the possibility of a higher profit margin. The Journal of Food Technology in Africa Volume 5 Number 2 (April - June 2000), pp. 62-63 KEY WORDS: Cocoa husk meal, layers mash, production performanc

Cottage processing of cashew apple juice in Nigeria: physico-chemical and sensory evaluation of product.

Some manually operated equipment were employed for cottage processing of cashew apples into juice. These include an extractor, mixer pasteuriser and a bottling machine. The apples were preheated with steam for 10, 20 and 30 minutes before juice extraction. The average capacity and efficiency of the extractor were 31.82g/hr and 87.20% respectively. Treatment time affected the colour, acidity and vitamin C content of the juice. Apples treated for 30 minutes gave a brownish colour (which was not acceptable to consumers) with the least amount of vitamin C (120.60mg/100ml of juice). The 10 minute extracted juice was attractive in terms of colour and acceptability. Soluble solids, pH, and specific gravity values of the juice were not affected by heat treatment. From the sensory evaluation of the products, no significant differences were obtained for taste, mouthfeel and overall acceptability. It was concluded that 10-minute treatment time was ideal for the juice extraction