• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.4
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• pp.439-449
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• 2018

In this paper, multi-objective optimization of a multi-bubble pressure cabin in the underwater glider with Blended-Wing-Body (BWB) is carried out using Kriging and the Non-dominated Sorting Genetic Algorithm (NSGA-II). Two objective functions are considered: buoyancy-weight ratio and internal volume. Multi-bubble pressure cabin has a strong compressive capacity, and makes full use of the fuselage space. Parametric modeling of the multi-bubble pressure cabin structure is automatic generated using UG secondary development. Finite Element Analysis (FEA) is employed to study the structural performance using the commercial software ANSYS. The weight of the primary structure is determined from the volume of the Finite Element Structure (FES). The stress limit is taken into account as the constraint condition. Finally, Technique for Ordering Preferences by Similarity to Ideal Solution (TOPSIS) method is used to find some trade-off optimum design points from all non-dominated optimum design points represented by the Pareto fronts. The best solution is compared with the initial design results to prove the efficiency and applicability of this optimization method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.3
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• pp.63-70
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• 2008

The purpose of this study is development of bridge design guidelines in Kangwondo mountain area. Much damages heve been wrought by Typhoon Rusa(2002), Maemi(2003), Ewinniar(2006) and severe rain storm in July 2006 in Kangwondo mountain area. The partial cause of these much damages are not consider the regional and geomorphologic condition of river in Kangwondo mountain area. Most of the bridge damages were caused by severe wash out the foundation of pier and abutment. As other reasons, dead trees, branches of the trees and floating materials were catched by pier and deck which make difficult or cut off the flow. Design guidelines are presented by analysis the types and reasons of damages of the disaster.

• Aerospace Engineering and Technology
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• v.12 no.1
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• pp.111-119
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• 2013

Conceptual design of RBCC (Rocket Based Combined Cycle) engine is performed through the thermodynamic cycle analysis. The engine is designed to take off at sea level and accelerate to Mach 8 at 30 km altitude. According to the flight speed, the engine operating modes are categorized into 3 modes : Ejectorjet (~ Mach 3), Ramjet (Mach 3~6), Scramjet (Mach 6~8). As a design result, the engine has a diameter of 1 m and a length of 6.7 m. In the prediction results, its maximum thrust is 16.5 ton. In Ramjet and Scramjet modes, design condition of the engine intake influence the engine thrust according to the flight speed.

• Journal of IKEEE
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• v.22 no.3
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• pp.539-547
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• 2018

Grid-connected inverter is required to cut off the power supplied to the grid at the islanding condition, immediately. For this reason, an islanding detection is an indispensable function for grid-connected distributed generation system. Slip-Mode frequency Shift (SMS) islanding detection method is very popular method to determine the grid state. SMS method supplies the reactive power to the load according to the grid frequency. In the islanding condition of grid, this injected reactive power pulls out the grid frequency from the allowable range, then the inverter system can detect the islanding condition of the grid. The SMS method can detect the islanding state well and does not generate any harmonics of the grid current. However, the reactive power would be generated and the power quality is reduced even though the grid is not islanding condition, but normal condition. In this paper, a modified SMS method is proposed to remove the reactive power in the normal condition. The performance of the proposed method is evaluated by 600W single phase inverter experimental results.

• Science of Emotion and Sensibility
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• v.7 no.1
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• pp.29-40
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• 2004

Even though rhythm is considered theoretically and practically as a form element influencing consumer's aesthetic response on product design, researches on it relatively less performed than other product aesthetic elements. And also existing researches have only suggested rhythm as one of aesthetic elements in product design but they haven't suggested overall insight on how to apply rhythm into product design. This study tested how rhythm expression in product design affects consumer's aesthetic response according to price level and brand hierarchy. The result shows that rhythm is clearly one of aesthetic elements. And rhythm expression increase consumer's aesthetic response in low priced product condition regardless of brand hierarchy. But in high priced product condition, rhythm expression decreases consumer's aesthetic response because of perceived risk. Only when in high prestige brand condition, consumer's aesthetic response remains high because of trade-off relationship between perceived risk and brand equity. The result of this study enables designers to understand characteristics of rhythm. Also, the result can give companies the useful way on how to use rhythm element as a strategic tool if they consider their brand equity level and product's price level.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.239-248
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• 2002

Bentonite slurries in a slurry wall construction must fulfill a stabilizing function by forming impermeable membrane (surface cake and penetrated cake) on the excavated soil faces. Thus problems are occurring in practice for the construction of diaphram walls and cut-off walls with a low permeability for wastes disposal areas in some deep excavations or different grounds. In this paper, the fundamental mechanics of fluid loss and filter cake formation in various soil beds are investigated using large scale laboratory apparatus. The sealing efficiency of filter cake from the large scale tests and the significance of fluid loss in a slurry trench are utilized for practical situation as a recommended design procedure.

• Aerospace Engineering and Technology
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• v.12 no.2
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• pp.193-201
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• 2013

Propeller is an important component of Human Powered Aircraft (HPA) propulsion system. HPA uses large diameter low rotational speed propeller to get high propeller efficiency. The propeller was designed by HPA propeller designing program. The propeller pitch is adjustable by rotating the blade axis angle at ground. Performance of the propeller for various parameters are analysed by the same program used for design. Off-design condition performance was also checked including pilot power change and flight speed change. The propeller was manufactured in ultra-light structure using carbon composite material down to 950g. The propeller was ground tested on ironbird and installed on KARI HPA. Finally the HPA flew 291m with this propeller.

• Journal of the Korean Society of Costume
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• v.58 no.9
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• pp.166-175
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• 2008

For the structural firefighting protective clothing, it can show a synergy effect when it satisfies smart fabric to block off a harmful environmental element and ergonomics design that apply range of motion of human body and appropriate size system. There are various standards about the structural firefighting protective clothing, but it's difficult to find a rule about movement suitability because the performance of the material holds a lot of the rules. Therefore, the purpose of this study is to propose a scheme to evaluate the current structural firefighting protective clothing and to improve movement suitability by research on the actual condition. For this, the survey about wearer acceptability scale on design and size and about improvement requirements was executed gathering firefighters' opinion. Questionnaire was composed with 23 items about satisfaction on current structural firefighting protective clothing, body suitability, movement suitability, improvement requirement and subjective information. As a results, Korean firefighters demand ergonomics design of structural firefighting protective clothing which to minimize restriction of body movement and to maximize body suitability.

• Food Science and Industry
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• v.50 no.2
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• pp.12-26
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• 2017

Processing steps such as washing and cutting, involved in preparing fresh-cut produce causes tissue damage, leading to rapid quality deterioration. Major defects of fresh-cut produce are discoloration, softening, off-odor development, and microbial growth. Packaging of fresh-cut produce has been changed to reduce these quality problems. Flexible packaging film is widely used to pack fresh-cut produce. Vacuum packaging was the popular packaging method in the beginning of fresh-cut industry in Korea. Vacuum packaging creates high $CO_2$ and low $O_2$ levels to control browning of fresh-cut produce. However, these conditions induce some visual defects and off-odor development. Discoloration problem was also found when fresh-cut produce was packaged with conventional packaging film or plastic tray. Modified atmosphere (MA) packaging is effective for prolonging shelf-life of fresh-cut produce by decreasing $O_2$ and increasing $CO_2$ concentration in the package. Retail MA packaging using different oxygen transmission rate (OTR) film and micro-perforated film has started to be applied to fresh-cut produce in Korea. Proper MA package design that provides optimum range of $O_2$ and $CO_2$ partial pressures is one of the major challenges in the industry. An initial package flushing with $N_2$ or an low $O_2$/high $CO_2$ atmosphere is also used to more rapidly establish steady-state MA condition. Film OTR and $O_2$ flushing affects the fermentative volatile production, off-odor development, electrolyte leakage, discoloration, $CO_2$ injury, microbial population of fresh-cut produce. There is also a demand for convenient packaging to attract consumers. Rigid fresh-cut produce container for retail market has increased since the packaging provides excellent protection from physical damage during transport. Rigid tray used as actual serving vessel for the consumer is increasing in Korea. The tray with flexible lid to wrap or seal fresh-cut produce is more and more gaining popularity. Further practical technology to control quality change and microbial growth for each fresh-cut product has been studied since various fresh-cut items were required. The fresh-cut industry also focuses on searching for more convenient and environmentally friendly packaging.

• Nuclear Engineering and Technology
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• v.45 no.5
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• pp.605-612
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• 2013

Removal of decay heat from an operating reactor during a prolonged station blackout condition is a big concern for reactor designers, especially after the recent Fukushima accident. In the case of a prolonged station blackout condition, heat removal is possible only by passive means since no pumps or active systems are available. Keeping this in mind, the AHWR has been designed with many passive safety features. One of them is a passive means of removing decay heat with the help of Isolation Condensers (ICs) which are submerged in a big water pool called the Gravity Driven Water Pool (GDWP). The ICs have many tubes in which the steam, generated by the reactor core due to the decay heat, flows and condenses by rejecting the heat into the water pool. After condensation, the condensate falls back into the steam drum of the reactor. The GDWP tank holds a large amount of water, about 8000 $m^3$, which is located at a higher elevation than the steam drum of the reactor in order to promote natural circulation. Due to the recent Fukushima type accidents, it has been a concern to understand and evaluate the capability of the ICs to remove decay heat for a prolonged period without escalating fuel sheath temperature. In view of this, an analysis has been performed for decay heat removal characteristics over several days of an AHWR by ICs. The computer code RELAP5/MOD3.2 was used for this purpose. Results indicate that the ICs can remove the decay heat for more than 10 days without causing any bulk boiling in the GDWP. After that, decay heat can be removed for more than 40 days by boiling off the pool inventory. The pressure inside the containment does not exceed the design pressure even after 10 days by condensation of steam generated from the GDWP on the walls of containment and on the Passive Containment Cooling System (PCCS) tubes. If venting is carried out after this period, the decay heat can be removed for more than 50 days without exceeding the design limits.