• Environmental Engineering Research
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• v.24 no.2
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• pp.347-353
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• 2019

Although membrane distillation (MD) has great promise for desalination of saline water sources, it is crucial to improve its thermal efficiency to reduce the operating cost. Accordingly, this study intended to examine the thermal energy efficiency of MD modules in a pilot scale system. Two different modules of hollow fiber membranes were compared in direct contact MD mode. One of them was made of polypropylene with the effective membrane area of $2.6m^2$ and the other was made of polyvinylidene fluoride with the effective membrane area of $7.6m^2$. The influence of operation parameters, including the temperatures of feed and distillate, feed flow rate, and distillate flow rate on the flux, recovery, and performance ratio (PR), was investigated. Results showed that the two MD membranes showed different flux and PR values even under similar conditions. Moreover, both flow rate and temperature difference between feed and distillate significantly affect the PR values. These results suggest that the operating conditions for MD should be determined by considering the module properties.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.7
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• pp.42-47
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• 2019

In this research, we try to study the change of squareness in the cutting process while changing cutting conditions such as feed rate and spindle rotational speed with chromium molybdenum steel (SCM415) material and TiCN, TiAlN coated end mill tool. The TiCN coating tool had the best straightness at 4,000 rpm at a feed rate of 200 mm/min. The TiAlN coating tool was best measured at 3,000 rpm at a feed rate of 200 mm/min. TiAlN coated tools had excellent dimensional tolerance when comparing the coating tool specifics.

• Journal of Biosystems Engineering
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• v.30 no.1 s.108
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• pp.8-16
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• 2005

The extrusion-cooking condition on Cordyceps pruinosa was designed using twin-screw extruder. Response surface methodology (RSM) was used to investigate extrusion-cooking using a central composition design with varying die temperature $(114-146^{\circ}C)$, feed moisture $(22-38\%)$, feed rate (4-14 ka/h) and screw speed (120-280 rpm). System parameters (die pressure and specific mechanical energy (SME)) and extrudate parameters (density and water solubility index (WSI)) were statically analyzed using RSH. Die pressure was significantly affected by temperature, moisture contents and feed rate. SM was affected by screw speed and feed rate. When die temperature is $130^{\circ}C$ and moisture content $25\%$, the optimum pressure is shown. SME is about 20 Wh/kg, when feed rate is $10\~12kg/min$ and screw speed $200\~250rpm$. WSI was affected by temperature and moisture contents. Density was not affected by any factor. WSI increases by $7\%$ from about $23\%$ to about $30\%$, as temperature is raised from $120^{\circ}C\;to\;140^{\circ}C$. The WSI of Cordyceps pruinosa pulverized after extruding (PE) is about $26.97\%$ higher than that of raw material and $10\%$ higher than that of pulverized after drying (PD). The content of unsaturated fatty acid were not significantly different in PD and PE. Anti-oxidative activity of PE was 1.67-2.2 times higher than that of PD in Cordyceps pruinosa using 1- dipheny1-2-picrylhydrazyl method (DPPH).

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.2
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• pp.6-11
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• 2000

In the pressurized propellant feed system of liquid rocket, feed pressure is decided chamber pressure of normal combustion state. However, during ignition period the initial chamber pressure is atmosphere. So, it may have overflow, hard-start and even critical damage of engine. This paper proposes an improved propellant feed system for the stable combustion of liquid rocket. Hot test were already performed to verify the presented propellent feed system. The proposed propellant feed system uses two steps - pre and main combustion - to prevent large pressure increase and uses cavitating venturis for stable flow rate in whole combustion. This system feeds the flow rate lesser than the designed flow rate, so combustion pressure reached pre-combustion pressure. Cavitating venturis offer unique flow control capabilities at normal and abnormal combustion state, because flow rate is solely dependent on upstream absolute pressure and fluid properties, but independent on downstream condition.

• Journal of Biosystems Engineering
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• v.12 no.4
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• pp.31-43
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• 1987

This study was performed to develop a hot water boiler system with small scale automatic rice hull furnace for the multi-purpose use in the farm. For the experiment a prototype hot water boiler system with rice hull furnace was fabricated, which was equipped with automatic hull feeder, igniter and ash removal device. Optimum operational conditions of the prototype: system were analyzed. The results arc summarized as follows. 1. The temperature measured right above the burning surface should be higher than $500^{\circ}C$ combustion. 2. The top zone of the combustion chamber was the most suitable location of the thermocouple to pick up the control temperature for the automatic operation of the rice hull furnace. 3. The content of carbon monoxide in the flue gas was increased with the filling height of burning material but it was less than 0.3 percent in volume in this experiment. When the filling height was expressed as the ratio of rice hull feed rate to the volume of the combustion chamber above the burning surface, the optimum ratio was about $150kg/m^3-h$. 4. The combustion efficiency of the prototype was higher than 95 percent when the feed rate was 1.1 to 2.3 kg/h and moisture content of rice hull was 22.4 percent (w.b.) or less. 5. It was estimated that the optimum operational conditions of the system were 1.3 to 2.0 kg/h in feed rate, 70 to 100 percent in excess air and 500 to $510^{\circ}C$ in control temperature. 6. The efficiency of coil heal exchanger increased with a decrease in feed rate of rice hull. When the rice hull feed rates were 1.1, 1.7 and 2.3 kg/h, the efficiencies of coil heat exchanger were about 34, 30 and 25 percent and heat transfer rates were 5.7, 7.6 and 8.8 MJ/h, respectively. When the flat plate heat exchanger was used in addition to the coil heat exchanger, the efficiency of the heat exchanger system increased to 48 percent.

• Journal of fish pathology
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• v.33 no.2
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• pp.177-184
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• 2020

In an attempt to find a feed additive showing an anti-scuticociliate effect, extracts from Citrus unshiu Peel were tested against virulent scuticociliate infection. The most effective anti-scuticociliate killing activity in vitro was observed in the extract squeezed from homogenizing water-soaked dried tangerine peel (DTP). In addition, we have investigated the effect of DTP as a feed additive on growth rate and anti-parasitic activity of olivaceus flounder. DTP extract added diets (0.1, 0.5, 1, and 5%/feed weight) were fed to flounder for 7 days for checking a growth rate and 14 days for a challenging test. As a result, the feed conversion rate was significantly improved only in 1% DPT extract group compared to the control and 0.5% DTP extract fed group showed 100% of survival rate in the challenge test, all of which indicating that DTP extract would be a potential feed additive against scuticociliatosis.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.4
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• pp.339-346
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• 2017

In this study, thermal performance test of VMD module was performed, prior to the construction of the demonstration plant using the vacuum membrane distillation (VMD) module of the capacity of $400m^3/day$ and to the commercialization of the VMD module. For the thermal performance test, the experimental equipment of capacity of $2m^3/day$ was constructed. The permeate flux test and thermal performance test according to feed water conditions such as temperature and flow rate were conducted. The VMD module used in the study was manufactured by ECONITY Co., LTD with PVDF hollow fiber membrane. As a result, the Performance Ratio (PR) of the VMD module showed the maximum value of 0.904 under the condition of feed water temperature of $75^{\circ}C$ and flow rate of $8m^3/h$. PR value of the VMD module using PVDF hollow fiber membrane showed linearly increasing relationship with feed water temperature and flow rate. Also, The permeate flux of the VMD module was analyzed to have maximum value of 18.25 LMH and the salt rejection was 99.99%.

• Fisheries and Aquatic Sciences
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• v.27 no.3
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• pp.195-205
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• 2024

Amphipoda is a benthic fauna occupying aquatic environments that can be used as a live feed for mud crabs. The abundance of amphipods in the water is thought to impact the preying capacity of crablets, which in turn will affect their growth performance. This study aims to determine the preying capacity of the crablet stage of Scylla tranquebarica exposed at different densities (20, 30, and 40 amphipods / 0.5 L) of amphipod, Grandidierella megnae. The preying capacity was estimated by counting the number of amphipods ingested by an individual crablet during the 60-day rearing period. The main parameters measured were daily consumption rate (DCR), Cumulative molting (CM), Feed conversion ratio (FCR), and the specific growth rate of weight (SGR-W). The results showed that the DCR and FCR were not affected by amphipod densities but the higher the amphipod density the higher the SGR-W and CM. Based on this study, 30 amphipods / 0.5 L is recommended as the optimal density to optimize the DCR and improve the growth performance of crablets. It is also proposed that surplus live feed will potentially reduce the cannibalism rate of crablets during weaning. However, more research needs to be carried out to elucidate the benefits of crablet-feeding amphipods in communal systems.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.1
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• pp.88-94
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• 2002

For the pressurized propellant supply system of liquid rocket, feed pressure is determined with respect to the chamber pressure of normal combustion state. However, during ignition period the initial chamber pressure is atmosopheric. This may cause overflow, hard-start and even critical damage for the engine. This paper proposes an improved propellant feed system for the stable combustion of liquid rocket. The proposed system utilizes the cavitating venturi to provide stable mass flow rate. Cavitating venturi offers unique flow control capabilities at normal and abnormal combustion state, because flow rate is soley dependent on the upstream absolute pressure and fluid properties, but independent on th downstream condition. Experimental variables are propellant feed pressure and chamber pressure. The effectiveness of cavitating venturi increased when the ratio of actual feed pressure to the cavitating venturi design pressure is increased. It is also found that Kerosene if more effective to supply stable mass flow rate than LOx.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.8
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• pp.139-149
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• 2001

The effects of the cutting conditions on the surface roughness of workpiece in turning were studied in this paper. The workpieces made of carbon steel SM20C and SM45C were tamed without the support of the tailstock center. Cutting conditions were changed in three or flour steps in each parameter and cutting fluid was used. The surface roughness results of tests were measured and the effects of the cutting conditions were analyzed by the method of analysis of variance. The summary of the experimental research is as follows. The main parameters were cutting speed, fred-rate, depth of cut, and the interactions between speed and fled-rate, speed and depth of cut, and fred and depth of cut. As cutting speed increased, surface roughness showed lower value. The surface roughnesses of feed-rate 0.102 mm/rev and 0.147 mm/rev were better than those of feed-rate 0.05 mm/rev and 0.2 mm/rev.