• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.6
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• pp.462-470
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• 2016

The locking load of a conventional manhole depends on the weight of its cover. Locking-type manhole structures with a special locking mechanism were recently developed to prevent accidents such as stolen cover, away cover from a frame. The weight of the manhole structure can be reduced under structural safety because the locking force of a locking-type manhole is greater than the weight of the cover. A light-weight manhole cover is developed in this study by using a finite element stress analysis and the design of experiments. Static stress analysis and fracture experiments are also conducted to analyze the states of the initial product. The optimum light-weight manhole cover considering manufacturing molds is developed and tested. Consequently, the weight was found to reduce by 16%. In addition, the fracture load increased by 38%.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.2 s.152
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• pp.139-147
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• 2007

The ultimate goal of structural design is to find the optimal design results which satisfies both safety and economy at the same time. Optimum design has been studied for the last several decades and is being studied. in this study, an optimum algorithm which is based on the genetic algorithm has been applied to the multi-object problem to obtain the optimum solutions which minimizes structural weight and construction cost of panel blocks in ship structures at the same time. Mathematical problems are dealt at first to justify the reliability of the present optimum algorithm. And then the present method has been applied to the panel block model which can be found in ship structures. From the present findings it has been seen that the present optimum algorithm can reasonably give the optimum design results.

• Journal of Korean Association for Spatial Structures
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• v.12 no.4
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• pp.47-56
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• 2012

This paper describes the structural design and optimization of sinusoidally corrugated web girder by using EUROCODE (EN 1993-1-5). The optimum design methodology and characteristics of the optimal cross-section are discussed. We investigate a shear buckling and the concerned standards for corrugated web and explain the equations to obtain a critical stress according to buckling type. In order to perform optimization, we consider an objective function as minimum weight of the girder and use the constraint functions as slenderness ratio and stresses of flanges as well as corrugated web and deflection. Genetic Algorithm is adopted to search a global optimum solution for this mathematical model. For numerical example, the clamped girder under the concentrated load is considered, while the optimum cross-sectional area and design variables are analyzed. From the results of the adopted example, the optimum design program of the sinusoidally corrugated web girder is able to find the suitable solution which satisfied a condition subject to constraint functions. The optimum design shows the tendency to decrease the cross-sectional area with the yielding strength increase and increase the areas with load increase. Moreover, the corrugated web thickness shows a stable increase concerning the load.

• Journal of Aquaculture
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• v.21 no.4
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• pp.244-251
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• 2008

We evaluated the optimum dietary lipid level and feeding rates of extruded pellets (EP) in juvenile flounder Paralichthys olivaceus during the summer season. The first experiment was conducted to determine the optimum dietary lipid level in juvenile flounder. Five isonitrogenous EP (52% crude protein) with increasing dietary lipids (6, 8, 10, 12 and 14%) were fed to satiety to triplicate groups of the juveniles ($18.4{\pm}0.11g$) twice a day for 6 weeks. Weight gain (WG) of fish fed EP with 10% lipid was significantly higher than those of fish fed EP with 6 and 14% lipid (P<0.05). Broken line model analysis suggested that the optimum dietary lipid level could be $9.08{\pm}0.37%$ for the maximum WG in juvenile flounder. The second experiment was conducted to determine the optimum feeding rate using experimental diet contained 10% lipid level that had the highest WG in first experiment. The feed intake of triplicate groups of the juveniles ($13.4{\pm}0.15g$) was restricted to four different feeding rates of 2.0, 2.5, 3.0 and 3.5% of their body weight $day^{-1}$ and to satiation using experimental diets. WG and feed efficiency (FE) of fish was affected by feeding rates. WG and specific growth rate of fish fed the diets increased with increasing feeding rate, however no significant differences (P>0.05) in WG and specific growth rate were observed between the fish fed 3.5% of their body weight $day^{-1}$ and to satiation. FE of fish fed 3.5% of their body weight $day^{-1}$ was significantly higher than those offish fed 2.0% of their body weight $day^{-1}$ and to satiation (P<0.05). Broken line model analysis suggested that the optimum dietary feeding rate could be $3.56{\pm}0.06%$ for the maximum WG in juvenile flounder. These results indicated that the optimum lipid level and feeding rate could be $9{\sim}10%$ (Energy: 4,774kcal and PIE ratio: 108mg protein/kcal in diet) and 3.5% of their body weight $day^{-1}$in juvenile flounder, respectively.

• Tribology and Lubricants
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• v.17 no.2
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• pp.146-152
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• 2001

Environmentally adapted synthetic base oils of polyalkylene glycols (PAGs) and polyol esters (POEs) show a high polarity because of their functional groups containing oxygen atom. The lubricating performance of these polar base oils was investigated by using a four-ball tribometer under boundary lubrication condition. Four polyalkylene glycols and five polyol ester base oils were used as sample base oils of high polarity. A mineral oil (MO) and alkylnaphthalene (AN) were used as low polarity base oils. Tricrecylphosphate (TCP) was added to all the base oils, in the range of 10 mmol/L-2000 mmol/L, as an antiwear additive. All the TCP-for-mutated base oils showed optimum concentration characteristics for minimizing wear. The order of optimum concentration of all the base oils was in a good accordance with the order of relative stability of TCP in base oils. The interaction model on solvation between additive and different polar base oils can expect the stability order of TCP. Thus, the model on solvation can explain well the order of optimum concentration of all the base oils, by using the effect of polarity (dielectric constant, $\varepsilon$) and molecular size (molecular weight, MW) of them on stability of TCP in polar base oils. Finally, a good correlation of the optimum concentration for all the base oils was obtained when it was arranged as a function of C∝(M $W_{Base Oil}$/M $W_{TCP}$)$^{-2}$.71/.($\varepsilon$$_{Base Oil}$)$^{3.38}$ by these two parameters.s..

• Journal of Aquaculture
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• v.6 no.1
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• pp.47-53
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• 1993

Feeding trials were conducted for a test of the optimum dietary protein levels for the fingerling Korean catfish, Parasilurus asotus. The growth response was examined in terms of weight gain, feed coefficient. protein efficiency ratio and net protein utilization for 8 weeks at $23\~27^{\circ}C$. Within a range of 25 to 55\%$ crude protein levels in the diet, the body weight increased while the dietary protein level increased. Accumulation of protein in the body reached the maximum when the crude protein level in the diet was at $45\%$. These results indicate that the optimum dietary protein level of fingerling Korean catfish was about $45\%$ when anchovy meal was used as the protein source.

• The KSFM Journal of Fluid Machinery
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• v.7 no.2 s.23
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• pp.7-13
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• 2004

In an attempt to solve multiobjective optimization problems, weighted sum method is most widely used for the advantage that a designer can consider the relative significance of each object functions by weight values but it can be highly sensitive to weight vector and occasionally yield a deviated optimum from the relative weighting values designer designated because the multiobjective function has the form of simple sum of the product of the weighting values and the object functions in traditional approach. To search the design solution agree well to the designer's weighting values, we proposed new multiobjective function which was the functional of each normalized objective functions and considered to find the design solution comparing the distance between the characteristic line and the ideal optimum. In this study, proposed multiobjective function was applied to design high efficiency and low noise axial flow fan and the result shows this approach is effective for the case that the quality of the design can be highly affected by the designer's subjectiveness represented as weighting values in multiobjective design optimization process.

• Journal of Electrochemical Science and Technology
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• v.9 no.2
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• pp.141-148
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• 2018

This study evaluated the performance characteristics of varied electrolyte species and amounts in a molten carbonate fuel cell (MCFC). Coin-type MCFCs were used at the condition of $650^{\circ}C$ and 1 atm. In order to measure the effects of varied electrolyte species and amounts, electrolytes of $(Li+K)_2CO_3$ and $(Li+Na)_2CO_3$ were selected and the amounts of 1.5 g, 2.0 g, 3.0 g, and 4.0 g were used. Insignificant performance differences were observed in the cell using different electrolytes, but the cell performance was sensitive to the amount of the electrolyte used. The pore-filling ratio (PFR), a ratio of pore filling in the components by the liquid carbonate electrolytes, was used to determine the optimum performance range. Consequently, 77% PFR demonstrated the optimum performance for both electrolytes. Thus, the MCFC had a permissible but narrow optimum performance range. The remaining amounts of electrolyte in the cells were determined using the weight reduction ratio (WRR) method after several hours of cell operation. The WRR used the relationship between the initial loaded amount of electrolyte and weight reduction of components in 10 wt% acetic acid. The relationships were linear and identical between the two electrolyte species.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.49 no.5
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• pp.381-388
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• 2004

In Korea, production of super sweet corn has been economically feasible and is substituting for traditional sweet corn due to better flavor in recent years. Major limiting factors for super sweet corn production are low field emergence and low seedling vigor. The optimum water potential (WP) for the priming of normal and aged seeds of dent, sweet (su) and super sweet (sh2) corns was studied to improve low seed quality. Seeds were primed at 0, -0.3, -0.6, -0.9, and -1.2 MPa of polyethylene glycol (PEG) 8000 solution at $15^{\circ}C$ for 2 days. Priming effects differed depending on the type of corn, seed quality, and WP of PEG solution. Although WP of priming solution did not influence the emergence rate of extremely high quality normal dent corn seeds, it reduced time to $50\%$ emergence (T50) and increased plumule weight. In contrast, the emergence rate of aged field corn was improved by seed priming at 0 MPa and plumule weight and $\alpha-amylase$ activity was enhanced. The optimum WP for both normal and aged sweet and super sweet corn seeds was between -0.3 and -0.6 Mpa. At the optimum WP emergence rate, $\alpha-amylase$ activity, and content of DNA and soluble protein increased, while T50 and leakage of total sugars and electrolytes reduced.

• Journal of the Korean Society of Food Science and Nutrition
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• v.26 no.5
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• pp.866-871
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• 1997

This study was carried out to determine the effect of osmotic dehydration as pretreatment on the qualities of dried cherry-tomatoes. The weight reduction and solid gain in osmosed cherry-tomato were increased by increasing sugar concentration, immersion temperature and time; among three parameters, the immersion temperature affected more than sugar concentration and immersion time did. The moisture content was decreased as increasing sugar concentration, immersion temperature and time, and it was the lowest at the osmotic conditions of 7$0^{\circ}C$, 60$^{\circ}$Brix and 11hr. To determine the optimum processing condition by RSm, the polynomial optimum models were established. The regression models was significant (p<0.05). It was used contour plots to optimize osmotic dehydration. The optimum condition for osmotic dehydration as pretreatments for drying of cherry-tomatoes were immersion temperature of 47~53$^{\circ}C$, sugar concentration of 39~43$^{\circ}$Brix, and immersion time of 7hr, in which process conditions were 78~86% moisture content, 8.5~10$^{\circ}$Brix sugar content and 80~86% weight reduction.