Design, Construction and Testing of a Hydraulic Power Take-Off for Wave Energy Converters

This paper presents the construction, mathematical modeling and testing of a scaled universal hydraulic Power Take-Off (PTO) device for Wave Energy Converters (WECs). A specific prototype and test bench were designed and built to carry out the tests. The results obtained from these tests were used to adjust an in-house mathematical model. The PTO was initially designed to be coupled to a scaled wave energy capture device with a low speed and high torque oscillating motion and high power fluctuations. Any Energy Capture Device (ECD) that fulfils these requirements can be coupled to this PTO, provided that its scale is adequately defined depending on the rated power of the full scale prototype. The initial calibration included estimation of the pressure drops in the different components, the pressurization time of the oil inside the hydraulic cylinders and the volumetric efficiency of the complete circuit. Since the overall efficiency measured during the tests ranged from 0.69 to 0.8 and the dynamic performance of the PTO was satisfactory, the results are really promising and it is believed that this solution might prove effective in real devices.

Design and construction of portable surface aeration pump for tanks and small ponds

The maintenance of adequate dissolved oxygen level is very important in the economy of any aquaculture system. An easy to construct aerating device was created using 0.5 hp water-pump, shower rose, Styrofoam, and rubber hose. The aerator works by drawing water from below and discharging it into the atmosphere as a spray. The spray is aerated as it splashes into the water surface. The aerating device has an average spray of 1.2 unit and doubles the dissolved oxygen content of 37.8 m super(3) tank in one hour

Construction, extension and evaluation of the improved smoking kiln (Banda) in Kainji Lake area

Fish smoking, as a traditional occupation of fishermen and women in Kainji Lake Area (Nigeria) is done using simple traditional ovens called 'Banda', the fuel for the smoking being almost hundred percent dependent on wood. A simple modification was made to the traditional 'Banda' oven using a damper to prevent burning of the fish. A comparison of the improved and the traditional 'Banda' was made. The results indicate that fuel wood consumption was reduced 52 percent by using the improved 'Banda', which implied that 50 percent of fish processor's income could be saved through the adoption of this technology. The most important advantage of the improved kiln, fuel wood conservation, represents for fishers a problem of an economic importance. Whilst they are aware that it is becoming much more difficult to get the needed fuel wood, the children can still conveniently collect enough wood for both home use and processing activities. The cost of the components of the improved kiln, when compared with the traditional version may be considered quite significant, and hence the reluctance of the fish processors in constructing similar ones. Selected blacksmiths were trained to continue the fabrication of the kiln component. The training was carried out to assure that the improved kiln will be constructed even after the project will end to support the fabrication

Preliminary study on the construction and management of integrated rice-cum-fish culture system at Karabande, New Bussa

Details are given of a study carried out in Nigeria, to introduce the practice of fish-cum-rice culture, using Sarotherodon galilaeus. Two plots each measuring 360m super(2) were used for this study and were compared with the farmer's two plots measuring 300m super(2) and 350m super(2). The plots were modified and had two central canals. Rice seedlings were transplanted into the plots after 19 days using a planting distance of 20 x 20cm. Three rice seedlings were planted per hole, using rice variety FARO 40, and grown for 90 days. About 240 and 180 S. galilaeus fingerlings of mean weight of 30g and 26g were stocked in the two experimental plots, respectively. They were fed with pelleted feed of 25% C.P. and monitored for 100 days. A yield of 22.8kg was obtained in plot A while 15.66kg was obtained in plot B. A rice yield of 250kg (i.e 5 bags) was obtained in each of the plots. The results obtained were compared with plots with no fish

Experimental and finite element studies of a large arch dam

Forced vibration field tests and finite element studies have been conducted on Morrow Point (arch) Dam in order to investigate dynamic dam-water interaction and water compressibility. Design of the data acquisition system incorporates several special features to retrieve both amplitude and phase of the response in a low signal to noise environment. These features contributed to the success of the experimental program which, for the first time, produced field evidence of water compressibility; this effect seems to play a significant role only in the symmetric response of Morrow Point Dam in the frequency range examined. In the accompanying analysis, frequency response curves for measured accelerations and water pressures as well as their resonating shapes are compared to predictions from the current state-of-the-art finite element model for which water compressibility is both included and neglected. Calibration of the numerical model employs the antisymmetric response data since they are only slightly affected by water compressibility, and, after calibration, good agreement to the data is obtained whether or not water compressibility is included. In the effort to reproduce the symmetric response data, on which water compressibility has a significant influence, the calibrated model shows better correlation when water compressibility is included, but the agreement is still inadequate. Similar results occur using data obtained previously by others at a low water level. A successful isolation of the fundamental water resonance from the experimental data shows significantly different features from those of the numerical water model, indicating possible inaccuracy in the assumed geometry and/or boundary conditions for the reservoir. However, the investigation does suggest possible directions in which the numerical model can be improved.

The integrated approach of water hyacinth control on Lake Kainji: with special regard to the design, construction and installation of a water hyacinth barrier across the River Niger

This document lists the undesirable effects of water hyacinth (Eichhornia crassipes) on fisheries in Lake Kainji (Nigeria) and the integrated Water Hyacinth Control Programme in its ongoing fisheries management and development activities on the lake. Special regard is given to the design, construction and installation of a water hyacinth barrier across the River Niger. (PDF contains 44 pages)

Survey of fungal infestation of some fish species from Tagwai dam, Minna, Niger State

Survey of Fungal infestation of some species of fish in Tagwai Dam Minna was carried out from March to June 2002. Fungi were isolated from the scale/skin, gills and fins. Twenty-one fungi species were identified from 18 species of fish microbial growth was measured by direct cell count using Stuart colony counter. Most of the fungi encountered were of the mould group and infestation occurred among all the species sampled. The infestation was predominantly by Aspergillus species and the scale/skin was most widely affected. The study showed the identified fungi in order of frequency to be as follows. Aspergillius niger. Rrhizopus spp. Mmucor spp Aspergilus flavum. Aspergillus parasitous. Aspergillus fumigatus, Microsporum canis. Penicillum virridicalumand Fusarium spp respectively. Aspergillus niger occurred on all the species of fish sampled. Barrilius spa and Chrysichrhy auratus longifilis had significantly higher (P<0.05) mean fungal load on their fins and gills. There was no significant difference (P>0.05) in the mean fungal load in different parts of the body of other fish species sampled

Occupational practices and problems of rural artisanal fisherfolks in Oyan Dam area of Ogun State

Artisanal Fish Societies constitutes one of the poorest societies in the developing world. Attempts to harness the potentials of the societies have often failed due to the enormity of the problem of poverty. This study was conducted in four major fishing villages namely; Abule titun, Apojola, Imama Odo and Ibaro in order to investigate the occupational practices and the problems of rural artisanal fisherfolks in Oyam's Dam, area of Ogun State. Eighty respondents were randomly selected among the artisanal fisher folks for interview using interview guide. The findings revealed that 43.8% of the fisherfolks are within active range of 31-40 years while 30% are within 21-30 years range. Also 31% had no formal education indicating a relatively high level of illiteracy among the fisherfolks while majority of the respondents practice fishing activities using paddle and canoe. It was similarly discovered from the study that the most pressing problems of the fisherfolks is the lack of basic social amenities like electricity, potable water, access roads, hospitals and markets. It is therefore recommended that basic social infrastructures be provided for the artisanal fishing communities in order to improve their social welfare, standard of living and the capacity to have a sustainable fishing occupation in the interest of food security and poverty alleviation

Hatchery construction and its feasibility in the Nigerian economy

Aquaculture drive in the Niger Delta has necessitated the springing up of various forms of hatcheries in Nigeria in the area. The hatchery level is high as most fish farmers now want to produce their own fingerlings for the stocking of their production ponds for culture to market (table) size. The paper shows that there is a lot of market in the Niger-Delta for fresh fish. Majority of the numerous fish farmers are not well empowered to breed and produce fish seeds especially species most loved and eaten. The rising cost of materials in the Nigerian economy has become a bottleneck in the construction of more fish hatcheries for fingerling production. However, the assistance of multinationals has become very necessary to enhance its feasibility to encourage better involvement in the fish hatchery works. One remarkable area where assistance is being felt by the communities in the Niger-Delta is in fish farming and more so in the supply of fish fingerling to top fish farmers by The Shell Petroleum Development Company of Nigeria Limited (SPDC), a multinational oil company in the area. Few fish farmers have benefited from this. If more hatcheries are available to service and provide the needed fingerlings to stock the available water bodies such as, home backyard ponds, the 0.74 million hectares of brackish water, 1.01 million hectares of perennial swamps, and other marginal land available for aquaculture and properly managed, it will yield between 2.5 and 10 metric tones of fish depending on the species stocked and bred

Occupational practice and problems of artisanal fisherfolk in Oyan dam area of Ogun State

Artisanal Fish Societies constitutes one of the poorest societies in the developing world. Attempts to harness the potentials of such societies have often failed due to the enormity of the problem of poverty. This study was conducted in four major fishing villages namely: Abule Titun, Apojola, Imala Odo and Ibaro in order to investigate the occupational practices and the problems of rural artisanal fisherfolks in Oyam's Dam, area of Ogun State. Eighty respondents were randomly selected among the artisanal fisher folks for interview using interview guide. The findings revealed that 43.8% of the fisherfolks are within active age range of 31-40 years while 30% are within 21-30 years range. Also 31% had no formal education indicating a relatively high level of illiteracy among the fisherfolks while majority of the respondents practice fishing activities using paddle and canoe. It was similarly discovered from the study that the most pressing problems of the fishfolks is the lack of basic social amenities like electricity, potable water, access roads, hospital and markets. It is therefore recommended that basic social infrastructures be provided for the artisanal fishing communities in order to improve their social welfare, standard of living and the capacity to have a sustainable fishing occupation in the interest of food security and poverty alleviation

Beyond the blur: Construction and characterization of the first autonomous AO system and An AO survey of magnetar proper motions

Adaptive optics (AO) corrects distortions created by atmospheric turbulence and delivers diffraction-limited images on ground-based telescopes. The vastly improved spatial resolution and sensitivity has been utilized for studying everything from the magnetic fields of sunspots upto the internal dynamics of high-redshift galaxies. This thesis about AO science from small and large telescopes is divided into two parts: Robo-AO and magnetar kinematics.

In the first part, I discuss the construction and performance of the world’s first fully autonomous visible light AO system, Robo-AO, at the Palomar 60-inch telescope. Robo-AO operates extremely efficiently with an overhead < 50s, typically observing about 22 targets every hour. We have performed large AO programs observing a total of over 7,500 targets since May 2012. In the visible band, the images have a Strehl ratio of about 10% and achieve a contrast of upto 6 magnitudes at a separation of 1′′. The full-width at half maximum achieved is 110–130 milli-arcsecond. I describe how Robo-AO is used to constrain the evolutionary models of low-mass pre-main-sequence stars by measuring resolved spectral energy distributions of stellar multiples in the visible band, more than doubling the current sample. I conclude this part with a discussion of possible future improvements to the Robo-AO system.

In the second part, I describe a study of magnetar kinematics using high-resolution near-infrared (NIR) AO imaging from the 10-meter Keck II telescope. Measuring the proper motions of five magnetars with a precision of upto 0.7 milli-arcsecond/yr, we have more than tripled the previously known sample of magnetar proper motions and proved that magnetar kinematics are equivalent to those of radio pulsars. We conclusively showed that SGR 1900+14 and SGR 1806-20 were ejected from the stellar clusters with which they were traditionally associated. The inferred kinematic ages of these two magnetars are 6±1.8 kyr and 650±300 yr respectively. These ages are a factor of three to four times greater than their respective characteristic ages. The calculated braking index is close to unity as compared to three for the vacuum dipole model and 2.5-2.8 as measured for young pulsars. I conclude this section by describing a search for NIR counterparts of new magnetars and a future promise of polarimetric investigation of a magnetars’ NIR emission mechanism.