Two-Phase Flow In Anode Flow Field Of A Small Direct Methanol Fuel Cell In Different Gravities

An in-situ visualization of two-phase flow inside anode flow bed of a small liquid fed direct methanol fuel cells in normal and reduced gravity has been conducted in a drop tower. The anode flow bed consists of 11 parallel straight channels. The length, width and depth of single channel, which had rectangular cross section, are 48.0, 2.5 and 2.0 mm, respectively. The rib width was 2.0 mm. The experimental results indicated that when the fuel cell orientation is vertical, two-phase flow pattern in anode channels can evolve from bubbly flow in normal gravity into slug flow in microgravity. The size of bubbles in the reduced gravity is also bigger. In microgravity, the bubbles rising speed in vertical channels is obviously slower than that in normal gravity. When the fuel cell orientation is horizontal, the slug flow in the reduced gravity has almost the same characteristic with that in normal gravity. It implies that the effect of gravity on two-phase flow is small and the bubbles removal is governed by viscous drag. When the gas slugs or gas columns occupy channels, the performance of liquid fed direct methanol fuel cells is failing rapidly. It infers that in long-term microgravity, flow bed and operating condition should be optimized to avoid concentration polarization of fuel cells.

Strategies for meeting the fishing input requirements of small scale artisanal fisheries

An examination is made of the socio-economic factors associated with the failure of existing approaches to the fishing input requirements of small-scale fisheries in Nigeria. The fishermen and secretaries of the fishermen cooperative societies in three major settlements (Uta-Ewa, Okoroete and Iko) were selected for interviews. The survey showed that the idealogy of the fishermen of the role of cooperative society is wrong and specific programmes need to be directed towards correcting this perception. Thus, for any meaningful support programme for the artisanal small-scale fishermen, the perception of the fishermen about the cooperative organization must first be aligned rightly. It is suggested that the fishing input be determined by type and specification as a preliminary step in the delivery of inputs to the fishermen. Social, economic and cultural variabilities should be related to the requirement by the fishermen. The price level of fishermen will determine the direction and level of government support required

Small angle X-ray scattering of the colloidal crystal

The monodisperse polystyrene spheres are assembled into the colloidal crystal on the glass substrate by vertical deposition method, which is aimed at the so-called photonic crystal applications. The structural information of the bulk colloidal crystal is crucial for understanding the crystal growth mechanism and developing the various applications of colloidal crystal. Small-angle X-ray scattering (SAXS) technique was used to obtain the bulk structure of the colloidal crystal at Beamline 1W2A of BSRF. It is found that the SAXS pattern is sensitive to the relative orientation between the colloidal sample and the incident X-ray direction. The crystal lattice was well distinguished and determined by the SAXS data.

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

The hydrology of a small fish pond at the University of Agriculture, Makurdi Experimental Fish Farm

The monthly and seasonal water requirements of a small fish pond (0.068ha; maximum capacity of 613.83m super(3)) at the University of Agriculture, Makurdi Fish Farm (Benue, Nigeria) were determined during the period of February to August 1996. The sources of water for the pond were rainfall, (103.4cm), run-off (6.3cm) and regulated inflow (95.0cm). The water loss for the period were Evapotranspiration, (106.74cm), Seepage (71.64cm) and regulated discharge (25.00cm). Evapotranspiration was identified as the main source of water loss while rainfall was the major source of water gain. The mean monthly water deficit was 24.56~c11.43cm while the mean monthly surplus was 9.84~c8.05cm. The quantity of water required to maintain the optimal water level in the pond was 474.00m super(3). Preliminary water budget of the study area showed that rainfed aquaculture can be effectively carried out at Makurdi during the months of June to October with supplementary inflows during the dry season months

Some aspects of the ecology and reproduction of the small pelagic cyprinid, Rastrineobola argentea in Lake Victoria

This study concentrated on the reproductive biology of the small pelagic cyprinid Rastrineobola argentea. The results indicate that this fish is an inshore spawning species, which agrees with other recent studies. It was also found that in areas where fishing intensity was likely to be relatively high, the size at first maturity of R. argentea was reduced, which is likely to be an effect of the fish altering its reproductive strategy according to life history theory. The CPUE results showed a general trend of decreasing with distance from shore, however areas less than one kilometer from the shore were not sampled. Evidence was also found suggesting that the cestode parasite, Ligula intestinalis had an adverse effect on the maturation and fecundity of R. argentea. Some management options concerning the findings in this study are also briefly discussed. (PDF has 82 pages)

Modeling on Runoff and Sediment Yield in Small Watersheds

The prediction and estimate of water and soil loss is fundamental important for understanding the effect of the spatial heterogeneity of underlying surfaces and preventing ecological environment deterioration. In this paper, a dynamic model of runoff and sediment yield in small watersheds is established. The proposed model includes three components: runoff generation caused by rainfall, soil erosion on hillslopes by overland flow, and runoff concentration and sediment transport on watersheds. Applying the proposed model, the runoff and sediment yield processes in a typical catchment on the loess plateau was estimated, which exhibited a good agreement between predicted results and observation.

Technological status and development prospects of small-scale fishing crafts in Nigerian coastal water

A study of fishing crafts was conducted in some coastal states of Nigeria to elucidate findings on the existing crafts as the baseline for further developments. Based on the technical designs, three types of fishing crafts were identified; planked, dug-out and half dug-out canoes. The planked canoes have the largest cubic number and dug-out canoes the least. At loadwater line, the ratio of freeboard to draft was 2 : 1 for planked canoes, indicating reserved buoyancy. Trim of planked canoe is by stern; the beam-length ratio for dug-out canoes showed high drag. Most of the sea-going canoes have U-shaped bottom hull profile capable of withstanding the rigours of surf landing and displayed good stability against longitudinal water wave. Gunwale and thwarts provided respectively the longitudinal and transverse strength of planked and half dug-out canoes. With its characteristics 'weight low down' construction, planked canoe represent the climax of small scale fishing crafts developments in Nigerian coastal waters. It's only draw back is durability. Further improvement in this canoe should be aimed at increasing the hull size and stiffness, water tightness of deck by coating, caulking, fastening, increasing level of motorization and installation of deck working equipments. Experimental design and use of fibre glass, aluminium and ferrocement hulls, together with improved planked canoe is highly advocated

Absorption of food in the black-jaw tilapia, Sarotherodon melanotheron (Ruppell) from a small tropical man-made lake in Ibadan, Nigeria

The carbohydrate, protein and lipid contents of the food ingested and their absorption in the intestine of Sarotherodon melanotheron inhabiting Awba lake in Ibadan, Nigeria, were investigated. Total carbohydrates of the ingested food ranged from 39.33 to 55.38% (mean = 48.70% while total protein and total lipid ranged from 10.10 to 17.13% (mean = 12.91%) and 7.79 to 8.96% (mean = 8.28%) dry weight, respectively. Calculated total percentages absorbed were 54.86-62.01 (mean 58.07) carbohydrates 47.33-54.06 (mean = 50.43) protein and 43.27-52.23% (mean 46.56) lipid. Absorption of protein and carbohydrate occurred mostly in the fore-gut (the first one-third of the intestine), while lipid was mostly absorbed in the mid-gut (the second one-third of the intestine). Dietary carbohydrate, protein and lipid contents of the food as well as the absorptive capacity of the intestine for these components of the food varied with size of fish

Small-scale fisheries resources management options - an overview: a key note address

Small-scale fisheries is traditional and rural based. Therefore, the paper is an over view of small-scale fisheries resources management in Nigeria. It provides about 80-90% employment to surrounding population. The small-scale fisheries are grouped in to two major sectors:- the artisanal or capture fisheries and aquaculture farming. The paper identified some management problems such as:- multi uses of the water bodies, lack of or inadequate data upon which sound management strategies are based, ownership of inland water bodies is a problem, uncontrolled exploitation hampers sustainable development, poor and low technology and lack of capital, land and credit facilities. The paper presented some management options for sustainable management. Measures to reduced fish spoilage have been advanced. Also highlighted is the role of fish culture in small-scale fisheries management

Sustainable management of water bodies for small-scale fisheries resorces research and development

Abstract The rapid growth of both formal and informal high density urban settlements around major water resources has led to increased pollution of streams, rivers, lakes and estuaries, due to contaminated runoff from these developments. The paper identified major contaminants to be : organic waste (sewage), industrial effluent, pesticides and litter. Pollutant loads vary depending on the hydrology of the urban area, local topography and soil conditions. In some instances, severe pollution of neighbouring and downstream water courses has been observed. The management of catchment land uses, riparian zones, in stream habitat, as well as in stream water flow patterns and quality are necessary in order to sustain the integrity and "health" of water resources, for fisheries and other developments. As such, attempts to ensure a certain level of water quality without attention to other aspects will not automatically ensure a "healthy" ecosystem even as fish habitat. Proper management leads to better water quality and conducive environment for increased fish production

The effect of traditional handling, processing and storage methods on the quality of dried fish in small scale fisheries in Nigeria

Most of the fish marketed throughout Nigeria are in either smoked or dried form. The technological requirement for other forms of preservation like chilling and freezing cannot be afforded by the small scale fisher folk. Considerable quantities of fish processed for distant consumer markets are lost at handling, processing, storage and marketing stages. Significant losses occur through infestation by mites, insects, fungal infestation and fragmentation during transportation. This paper attempts to describe the effect of these losses on fish quality and suggests methods of protecting fish from agents of deterioration