• Asian-Australasian Journal of Animal Sciences
• /
• v.27 no.7
• /
• pp.974-980
• /
• 2014

In semi-arid areas of Southern Africa, dehydration can compromise the performance and welfare of local chickens, particularly during the growing period when confinement is curtailed and birds are left to scavenge for feed and water. The effect of water restriction on the growth performance was compared in Naked Neck (NNK) and Ovambo (OVB) chickens that are predominant in Southern Africa. A total of 54 eight-wk-old pullets each of NNK and OVB chickens with an initial average weight of $641{\pm}10g/bird$ were randomly assigned to three water intake treatments, each having six birds for 8 wk. The water restriction treatments were ad libitum, 70% of ad libitum and 40% of ad libitum intake. Nine experimental pens with a floor space of $3.3m^2$ per strain were used. The pens were housed in an open-sided house with cement floor deep littered with a 20 cm layer of untreated wood shavings. Feed was provided ad libitum. Average daily water intake (ADWI), BW at 16 weeks of age (FBW), ADG, ADFI, feed conversion ratio (FCR) and water to feed ratios (WFR) were determined. Ovambo chickens had superior (p<0.05) FBW, ADG and ADWI than NNK chickens. Body weight of birds at 16 weeks of age, ADG, ADFI, ADWI, and WFR declined progressively (p<0.05) with increasing severity of water restriction while FCR values increased (p<0.05) as the severity of water restriction increased. Naked Neck chickens had better FCR at the 40% of ad libitum water intake level than Ovambo chickens. The dressing percentage per bird was higher in water restricted birds than those on ad libitum water consumption, irrespective of strain. Heart weight was significantly lower in birds on 40% of ad libitum water intake than those on ad libitum and 70% of ad libitum water intake, respectively. In conclusion, NNK chickens performed better than OVB chickens under conditions of water restriction and would be ideal to raise for meat and egg production in locations where water shortages are a major challenge.

• Applied Chemistry for Engineering
• /
• v.28 no.1
• /
• pp.118-124
• /
• 2017

An air cooling, open cathode type polymer electrolyte membrane fuel cell (PEMFC) has the advantages of system simplification and cost effectiveness. Open cathode PEMFC could suffer from reduced performance due to the membrane dehydration in low humidity of air. Effects of the cathode air flow rate, anode purge interval and long term storage on PEMFC performance were investigated in this work. Fan voltage is an important factor on air cooling PEMFC performance because the cathode air flow rate and stack temperature were controlled by fan voltage. The dead ended anode (DEA) method was applied to increase hydrogen usage. Periodical purge was used to discharge accumulated water and gas. The influence of long term non-operating condition on PEMFC performance degradation due to the membrane dehydration was also studied and the quick recovery method was developed.

• Proceedings of the Korean Society of Agricultural Engineers Conference
• /
• 2003.10a
• /
• pp.615-618
• /
• 2003

A prototype of 76 ha Shi-hwa constructed wetland was constructed for the first time in Korea to purify severely polluted stream water. Hydrology, vegetation(macrophyte) and water quality for Banwol and Donghwa wetland built in Shi-hwa tidal reclaimed area were monitored to evaluate the performance of the wetlands. The overall efficiency for the treatment of polluted stream water using the wetlands showed no significant improvement. The monthly average removal rates on SS, BOD, TN and TP for Banwol and Donghwa wetlands showed 66.5% and 62.8%, 14.8 and 34.3%, 33.9 and 47.1% and 20.8 and 51.6%, respectively. It is considered that three major factors, ie. wide fluctuations in inflow rate, short hydraulic retention time and small open area compared with vegetated area could have a great influence on low system efficiency.

• Journal of the Society of Naval Architects of Korea
• /
• v.43 no.1 s.145
• /
• pp.43-49
• /
• 2006

The hull form of icebreaking tanker depends on the trade route and ice characteristic. The hull form has to be designed for icebreaking concept if the vessel is operating in heavy ice and also the hull from has to be optimized for general tanker when the ship is operating in ice-free ocean. This paper presents comparison of ship resistance in pack ice, level ice and open water. Four ships are used to compare the resistance characteristic. One is conventional tanker and three ships are icebreaking tankers. The ice model test was carried out at the IOT (Institute for Ocean Technology, Newfoundland, Canada) and open water test was performed at 55MB (Samsung Ship Model Basin). The ice resistance of conventional tanker was predicted by Colbourne's method. The resistance of open water, pack ice and level ice are compared and discussed. The best hull form of icebreaker is not good in open water performance compare to conventional tanker. This result explains that the hull form of icebreaker and normal tanker have to compromise when the ship is operated in ice and ice-free condition. The result of this paper gives a guide for icebreaking tanker design.

• The KSFM Journal of Fluid Machinery
• /
• v.17 no.5
• /
• pp.19-26
• /
• 2014

The cross flow turbine attracts more and more attention for its relatively wide operating range and simple structure. In this study, a novel type of micro cross flow turbine is developed for application to a step in an irrigational channel. The head of the turbine is only H=4.3m and the turbine inlet channel is open ducted type, which has barely been studied. The efficiency of the turbine with inlet open duct channel is relatively low. Therefore, a guide nozzle on the turbine inlet is attached to improve the performance of the turbine. The guide nozzle shapes are investigated to find the best shape for the turbine. The guide nozzle plays an important role on directing flow at the runner entry, and it also decreases the negative torque loss by reducing the pressure difference in Region 1. There is 12.5% of efficiency improvement by attaching a well shaped guide nozzle on the turbine inlet.

• International Journal of Fluid Machinery and Systems
• /
• v.4 no.4
• /
• pp.396-409
• /
• 2011

Water turbines have been used in electricity generation for well over a century. Hydroelectricity now supplies 19% of world electricity. Many hydro power plants are operated with Pelton turbines, which is an impulse turbine. The main reasons for using impulse turbines are that they are very simple and relatively cheap. As the stream flow varies, water flow to the turbine can be easily controlled by changing the number of nozzles or by using adjustable nozzles. Scientific investigation and design of turbines saw rapid advancement during last century. Most of the research that had been done on turbines were focused on improving the performance with particular reference to turbine components such as shaft seals, speed increasers and bearings. There is not much information available on effects of blade friction on the performance of turbine. The main focus in this paper is to analyze the performance of Pelton turbine particularly with respect to their blade friction.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.15 no.6
• /
• pp.461-470
• /
• 2003

The purpose of this study is to investigate the performance of a transcritical cycle for hot water heating using $CO_2$ as a working fluid. Some of the main parameters that affect the practical performance of the $CO_2$ system are discussed; the performance on the variation of refrigerant charge, changes in flow conditions of secondary fluids, and that with or without internal heat exchanger, The experimental results show that the optimum charge is approximately the same for various mass flow rates of the secondary fluid at gas cooler. The experimental results on the effect of secondary fluids are in general agreement with the experimental results of transcritical cycle in the open literature and show similar trend for conventional subcritical vapor compression cycles. The heat exchanger effectiveness increases with an increase of the heat exchange area of the internal heat exchanger regardless of the mass flow rate at the gas cooler.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2001.11a
• /
• pp.52-57
• /
• 2001

In order to control hydration heat in mass concrete, pipe cooling method has been widely used. The pipe cooling method leads to the decrease of curing period by lagging materials as well as the decrease of temperature difference between center and surface of mass concrete member, There are two methods in the pipe cooling system, which are open loop system and closed loop system. However open loop pipe cooling system cannot be applied to the mass concrete structures when cooling water supply is difficult. To control hydration heat of high strength mass foundation in the central area of city, closed loop pipe cooling system was developed to solve the cooling water supply. This paper reports the performance results of hydration heat control with closed loop pipe cooling system.

• Corrosion Science and Technology
• /
• v.7 no.1
• /
• pp.61-67
• /
• 2008

In this paper, electrochemical and microstructural characteristics of nickel-plated Alloy 600 were investigated in order to identify the performance of electroless Ni-plating on Alloy 600 in high-temperature aqueous condition with the comparison of electrolytic nickel-plating. For high temperature corrosion test of nickel-plated Alloy 600, specimens were exposed for 770 hours to typical PWR primary water condition. During the test, open circuit potentials (OCP's) of all specimens were measured using a reference electrode. Also, resistance to flow accelerated corrosion (FAC) test was examined in order to check the durability of plated layers in high-velocity flow environment at high temperature. After exposures to high flow rate aqueous condition, the integrity of surfaces was confirmed by using both scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). For the field application, a remote process for electroless nickel-plating was demonstrated using a plate specimen with narrow gap on a laboratory scale. Finally, a practical seal design was suggested for more convenient application.

• Journal of Advanced Marine Engineering and Technology
• /
• v.31 no.5
• /
• pp.614-621
• /
• 2007

The fishing boat propulsion system employing the modified stern shape and the tunnel to protect a propeller is developed to increase the cruise speed and reduce he problem resulting from the open propeller accidentally catching the waste net and able on the sea. Using 3 different tunnel types, the model test was performed in the circular water channel and the panel method based on the potential theory is applied to analyze the open water performance of the propeller. In the numerical analysis using he potential-based panel method, it calculates the hydrodynamic interaction between the propeller and the tunnel and evaluates the effect of the tunnel geometry. From the numerical and experimental results differing tunnel geometries, the propulsion efficiency is increased by the larger diameter of the inlet than the outlet of the tunnel and the smaller gap between the propeller tip and the tunnel internal surface. These results provide the information of the propeller system with the tunnel and the hydrodynamic interaction between the propeller and the tunnel.