Effect of darting phenomenon of African catfish Heterobranchus longifilis (Burchell 1822) on growth performance of Nile tilapia: Oreochromis niloticus (Linnaeus, 1758)

Replicate Ponds of 0.02ha stocked at 500 catfishes with 20,000 tilapia/ha were used to assess growth performance of O.niloticus, average weight 50.4g with (i) darted catfish; H.longifilis (shooters) average weight 60.3g (ii) non-shooters of H.longifilis, average weight 35.4g. Final mean weight, mean growth rate, specific growth rate and food conversion ratio were 499.5g 26g/day, 1.36% and 5.58% respectively for O.niloticus stocked with longifilis (shooters) and 440.4g 2.3g/day 1.23% and 5.58% respectively for O.niloticus stocked with H.longifilis (non- shooters) and 246.9g, 1.2g/day, 0.93, 6.30% respectively for tilapia in monoculture. The least growth was noted for O. niloticus in monoculture while the best growth was recorded O. niloticus in polyculture with darted catfis

Optimizing the surface integrity of machined Ti-6A-4V using advanced carbide inserts and minimum quantity lubrication

A thesis submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Masters of Science in Engineering, 2016This research is focused on optimizing the surface integrity of Ti-6Al-4V using advanced carbide inserts and minimum quantity lubrication (MQL). Experiments were designed to machine twenty Ti-6Al-4V blocks under dry and MQL lubricating conditions using innovative cemented carbide inserts produced by Liquid Phase Sintering (LPS) and Spark Plasma Sintering (SPS). The cutting speed, feed rate, and depth of cut, were considered as machining parameters, while the cutting force, temperature, tool wear, surface roughness and residual stress were considered as performance characteristics. The results obtained for surface roughness and residual stress measurements were used to analyze the surface integrity of the machined Ti-6Al-4V samples. The influence of sintering techniques and milling parameters on performance characteristics and surface integrity were investigated from experimental results obtained. Discrepancy in behavioral trends with respect to lubricating conditions was also investigated. The analyses of milling results showed that cutting speed played a major role in the optimization of surface integrity of the Ti-6Al-4V work pieces followed by the depth of cut. The results also showed that the LPS inserts performed better than the SPS inserts due to their better mechanical properties (higher fracture toughness (KIC) and transverse rupture strength). The application of MQL was also observed to significantly reduce milling temperatures resulting in better surface integrity. However, an optimized surface integrity of the Ti-6Al-4V samples was achieved during MQL milling with the 10Co-L insert at a low finishing speed of 75m/minute and a reduced depth of cut of 0.5mm

ENTREPRENEURIAL ORIENTATION, COLLABORATIVE NETWORKS, AND NONPROFIT PERFORMANCE

In this mixed-method study, I explore the idea that an entrepreneurial orientation serves as a key driver of nonprofit organizational performance, and that a focal nonprofit’s set of collaborative ties moderates that relationship. I theorize that for nonprofits operating in an environment characterized by resource scarcity, possessing an EO is vital. More specifically, I theorize that organizations with smaller and less heterogeneous sets of collaborative ties benefit more from an EO than those with larger and more heterogeneous sets. I also explore the possibility that a focal nonprofit’s pattern of collaborative ties may be a function of that nonprofit’s EO. These ideas are tested using an original data set collected from a sample of the estimated 200 economic development organizations operating in eastern Kentucky. This is an area where economic growth has been particularly elusive, and where a deeper understanding of the entrepreneurial and collaborative practices of nonprofits might be especially valuable. The results reveal some significant empirical support for these ideas, and point to a promising research program aiming to uncover the interactive effects of EO, collaborative networks, and nonprofit performance across a range of organizational contexts

Laser assisted arc welding process for dry hyperbaric deep water application

Hyperbaric Gas Metal Arc Welding (GMAW) is an important technology for repair welding of deep sea pipelines and linking of existing pipeline networks to newer ones through tie-ins and hot-tap welding. With increasing water depth the process becomes susceptible to hydrogen assisted cracking due to the very fast cooling rate of the weld caused by higher habitat gas density and resulting higher thermal diffusivity. Maintaining sufficient heat in the welding zone is vital to avoid a potential cracking tendency especially as moisture pick-up may be difficult to avoid during hyperbaric welding operations. In addition to this, hyperbaric GMAW has a limitation of low heat input because it is operated at a short arc length or dip transfer mode to avoid process instability at high pressure. Also, the short arc length generates weld spatter that may affect weld quality. The research presented in this thesis, investigated the use of an industrial laser in conduction mode for the purpose of providing significant additional heat input to control the weld thermal cycles of GMAW. Advanced GMAW power sources such as the Fronius Cold Metal Transfer (CMT) and EWM ColdArc have also been investigated for reduced weld spatter generation. Studies were conducted to investigate the weld pool thermal cycles and resulting metallurgical phase formation in hyperbaric GMAW at different pressures ranging from 1 bar to 200 bar. This was followed by welding trials at one atmosphere to compare the process characteristics of traditional dip transfer GMAW with some advanced GMAW power sources such as CMT and ColdArc. The main experimental trials to investigate a laser assisted GMAW (CMT) process were performed at one atmosphere condition. A thermal model was developed using Abaqus software to predict the weld metal and heat affected zone thermal cycle in a laser assisted GMAW (CMT) process at one atmosphere and under high ambient pressures. Finally, investigation was carried out to evaluate the benefit of the laser assisted process in lowering diffusible hydrogen content from the weld metal. The hyperbaric GMAW experimental results showed that the weld pool cooling rate increases with pressure due to higher chamber gas density and resulting thermal diffusivity. But this effect is not prominent for thicker plates. Therefore, it was concluded that heat conduction through the steel thickness dominates convective losses to the chamber gas environment. It was also shown that the welding arc shrinks as pressure increases in order to minimise energy loss to the environment. This defined the weld bead profile; although it was found that beyond 100 bar pressure the weld penetration depth remained effectively unchanged. Apart from the hardness of the weld made at 1 bar, there was little difference between those at 18, 100 and 200 bar. However, all of the welds show hardness peaks greater than 350 HV10 recommended for offshore structures. It was observed that CMT produced the lowest weld spatter compared to the traditional GMAW and ColdArc. However, this advantage is constrained to low wire feed speed (3 to 5 m/min) beyond which it becomes relatively unstable. For the laser assisted GMAW (CMT) trials, it was shown that the laser serves as a spatially resolved heat source, reheating the weld bead and reducing the cooling rate. For the laser parameters investigated, over 200% reduction of cooling rate could be achieved when compared with GMAW alone. It was also demonstrated that the additional laser thermal input will extend the weld residence time at high temperature (over 300 °C). This will prolong the weld cooling time such that dissolved hydrogen can diffuse out before it comes to room temperature. The laser was shown to significantly reduce the weld peak hardness from about 420 HV0.5 to values below 350 HV0.5, which will be beneficial for hyperbaric welding. The model prediction of the weld thermal cycles was in good agreement with the experimental results. Therefore, it could be used to predict the weld metal and HAZ cooling rate of a laser assisted GMAW (CMT) process although the model would need to be calibrated for higher pressure data. It was also demonstrated that additional laser heat can reduce the weld hydrogen content to acceptable limits of 5 ml/100 g of weld metal even for high moisture content in the welding environment. In conclusion, the addition of laser heating to GMAW will reduce the weld cooling rate, extend the weld pool cooling time, and expel diffusible weld hydrogen. All of these would be immensely beneficial in terms of improving the quality and reliability of structures fabricated through hyperbaric GMAW

Analysis of urban poverty and its implications on development in Uyo urban, Akwa Ibom State

Concern for studies on urban poverty has been of low priority to  government, researchers and development planners in Nigeria. For over two decades, studies have been focused on rural poverty. This study therefore, investigated the present poverty situation in Uyo urban area and identified the vulnerable groups and their spatial dimension. The study adopted a survey research design in data collection. Descriptive and inferential statistics were used to analyse the data gathered from 20 sampled units in the study area Factor analysis technique was used to determine the different levels of poverty in the study area. The study revealed significant relationship between factorsof urban poverty and development in Uyo urban area. The study  recommended the formulation and implementation of policies by Government that would provide employment, housing, education,  improved health care among others for the urban poor

Irrigation potential of Inuakpa in Odukpani local government of Cross river using Kostiakov model

Infiltration measurements were carried out using cylindrical infiltrometer with height and diameter of 15cm and 5cm respectively. Sixteen infiltration runs were carried out in a composite grid (30m x 30m) in Inuakpa, Odukpani Local Government Area of Cross River State to test the efficiency of Kostiakov’s model, measure infiltration rate and relate same to some soil physical properties. Mean infiltration rate of 9.01 cmhr-1 was obtained at the end of the runs. The soil textural class was loamy sand with particle size distribution indicating mean values of 82.4, 7.2 and 10.4 % for sand, silt and clay respectively. The bulk density, particle density and total porosity had mean values of 1.35 Mgm-3, 2.48 Mgm-3 and 44.86 % while their coefficients of correlation with infiltration rate where 0.58, 0.48 and 0.69 respectively. There were also linear and positive relationships between infiltration rate and sand and silt contents with coefficients of correlation of 0.92** and 0.55* (p ≤ 0.05) respectively while clay content was not specifically linear or positive. Kostiakov infiltration model fitted well in evaluating infiltration parameters for sustained agricultural production. The soil infiltration rate, physical and chemical properties studied placed the soil in class 2 - irrigable. Mulching with plant residues, cover cropping, the use of restorative crops and zero tillage should be practiced in the area as soil management strategies

PROPERTIES OF CHITIN REINFORCES COMPOSITES: A REVIEW

This paper provides a review of chitin, sources, extraction, uses, applications, chitin whiskers and it preparations and the mechanical and thermal properties of chitin reinforced composites. Also reported here is the properties of CaCO3/chitin whiskers reinforced composites. Chitin can be extracted from shrimps, crabs cell walls, yeast and green algae or from Riftia tubes with a percentage varying between 20 to 40% depending on the source. Despite the denaturing of chitin, the most widely used method of extractiong chitin from seashells is the chemical method. Chitin whiskers known by different name in literature can only be prepared by using hydrochloric acid. The rod-like particles of chitin whiskers have an average lengths and widths of 200 ± 20 nm and 8 ± 1 nm respectively or more depending on the source of chitin. Chitin whiskers reinforced composites have greatly improved the mechanical and thermal properties of the composites especially at lower filler loading. The improved properties are attributed to effective stress transfer. http://dx.doi.org/10.4314/njt.v36i1.