• Advances in nano research
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• 제9권4호
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• pp.221-235
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• 2020

The following composition establishes a nonlocal strain gradient plate model that is essentially related to mass sensors laying on Winkler-Pasternak medium for the vibrational analysis from graphene sheets. To achieve a seemingly accurate study of graphene sheets, the posited theorem actually accommodates two parameters of scale in relation to the gradient of the strain as well as non-local results. Model graphene sheets are known to have double variant shear deformation plate theory without factors from shear correction. By using the principle of Hamilton, to acquire the governing equations of a non-local strain gradient graphene layer on an elastic substrate, Galerkin's method is therefore used to explicate the equations that govern various partition conditions. The influence of diverse factors like the magnetic field as well as the elastic foundation on graphene sheet's vibration characteristics, the number of nanoparticles, nonlocal parameter, nanoparticle mass as well as the length scale parameter had been evaluated.

• 대한조선학회논문집
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• 제45권1호
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• pp.93-100
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• 2008

There are two ways of conventional thermal distortion analysis. One is the thermal elasto-plastic analysis and the other is the equivalent forces method based on inherent strain. The former needs exorbitant analysis time, while the latter cannot obtain results of stress field and it needs much time consumption with loads modeling on curved plates. Such faults in two methods have made difficulties in thermal distortion analysis of a large structure like ship hull. In order to solve them, new kind of thermal distortion analysis method was developed. We devised that the inherent strains was used as direct input factors in forms of boundary conditions. It was embodied by using thermal expansion coefficient in commercial code. We used the pre-calculated inherent strain as thermal expansion coefficient, and endowed nodes with imaginary temperatures. This method was already adopted at hull block welding distortion analysis which was considered as impossible, and gave productive results such as reduction of work time in the dry dock.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.293-299
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• 2009

Many kinds of problems by stack effect occur in the high-rise buildings that have the simple plan on the first floor designed only by an external wall and an E/V shaft wall. Therefore, some buildings in the foreign countries has made the additional inside walls between lobby and E/V hall as a countermeasure on stack effect. An additional wall in the lobby is very useful countermeasure on stack problems because lobby is a main airflow path in the building. Decreasing effect on stack problems by an additional wall of lobby is reported in this study. An ordinary office building that has a simple lobby plan is simulated and measured in this study. The results show that characteristics on stack effect are changed by methods of applying additional walls and that alternations of countermeasures which building conditions like the kinds of problems and the problem's velocity etc. are considered are very important.

• 고려인삼학회:학술대회논문집
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• 고려인삼학회 1987년도 Proceedings of Korea-Japan Panax Ginseng Symposium 1987 Seoul Korea
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• pp.89-107
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• 1987

For the elucidation of significance of saponin as quality criterion of ginseng ginsenoside content(GC) and ginsenoside pattern similarity(GPS) by simple correlation were investigated in relation to red ginseng quality factors, age, plant part, harvest season, mineral nutrition, soil physical characteristics, growth light and temperature, shading material, growth location, physiological disease and crop stand through survey of ginseng plantstions, field experiments, water culture and phytotron experiments. Effect of tissue culture was also reviewed. GC was negatively correlated with good quality of red ·ginseng and positively with bad quality. Age did not show any consistency with GC but GPS was less with the increase of age difference. GPS was less or not significant between taproot that is lowest in GC and epidermis highest, and significant between leaf and taproot. Harvest season marked with the lowest GC and Pattern was also different. Nutrient imbalance, the increase of hazardous soil nutrient and physical condition to growth increased GC, but GPS was little different. The higher the growth lights intensity and temperature the higher the GC but GPS was little changed. Root rust increased GC, but root scab decreased it. Sponge-like and inside cavity phenomena increased GC. Ginsenoside pattern of cultured tissues and rootlet showed great variation. These results strongly indicate that there are optimum saponin content and ginsenoside pattern and that these are accomplished under the optimum growth condition.

• 한국공간구조학회논문집
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• 제17권4호
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• pp.133-140
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• 2017

Recently, the interest in the smart buildings is increasing in the architecture field. Among them, a research of facade design using a transformable system that can adjust the effect of the external environment is in progress. One of a typical example of the deployable system is a Scissors system that can change shape by using the geometric conditions of a unit member. Scissors system is a high-tech structural system which can construct the deployable plan and curved space by using the SLE (Scissors-Like Element) consisted of two Bar and Pivot. If the facade is designed by applying Scissors system, it is possible to maximize the performance and aesthetic effect of the structure by using a shape change of the line member. This paper presents a study of deployable facade design applying hybrid-typed Scissors system. A new deployable pattern of facade design is developed by combining Angulated Scissors system and tessellation pattern. Applying the deployable pattern a double skin construction method which is to add an outer wall for design, it raises three dimensional effects and can maximize the artistic essence of the change in shape upon deployment.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.414-419
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• 2011

Missile am fighter aircraft have been challenged by low restoring nose-down pitching moment at high angle of attach. The consequence of weak nose-down pitching moment can be resulting in a deep stall condition. Especially, the pressure oscillation has a huge effect on noise generation, structure damage, aerodynamic performance and safety, because the flow has strong unsteadiness at high angle of attack. In this paper, the unsteady aerodynamics coefficients were analyzed at high angle of attack up to 60 degrees around two dimensional NACA0012 airfoil. The two dimensional unsteady compressible Navier-Stokes equation with a LES turbulent model was calculated by OHOC (Optimized High-Order Compact) scheme. The flow conditions are Mach number of 0.3 and Reynolds number of $10^5$. The lift, drag, pressure distribution, etc. are analyzed according to the angle of attack. The results at a low angle of attack are compared with other results before a stall condition. From a certain high angle of attack, the strong vortex formed by the leading edge are flowing downstream as like Karman vortex around a circular cylinder. Unsteady velocity field, periodic vortex shedding, the unsteady pressure distribution on the airfoil surface, and the acoustic fields are analyzed. The effects of these unsteady characteristics in the aerodynamic coefficients are analyzed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.228-230
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• 2002

Recently, electric power reliability of our country has been improved. However, there are still remaining problems which are short-duration variations like instantaneous and momentary interruption and voltage sag by nature calamity ; typhoon, lightning, snow, etc. Besides, power quality ; harmonics, caused by using power electronics equipments, become a hot issue Malfunction of controller and stop machinery, and losing the important data are caused by poor power quality at a couple of second. Due to those, UPS, which is made up battery, has being used, but there are several disadvantages ; long charge and discharge time, environmental problem by acid and heavy metal, and short life time. As generally know, micro-SMES is a method to settle those mentioned. However, there need huge system apparatuses in order to verify the effect of system efficiency and stability considering the size of micro-SMES, the sort of converter type, and various conditions ; inner temperature, magnetic field, quench characteristic of micro-SMES, and etc. In this paper, in order to bring the mentioned above to a settlement, a micro-SMES is modeled with characteristics of micro-SMES is interfaced to EMTOC program using Fortran program interface method. We obtained hopeful answers and made the simulation model of micro SMES.

• 한국압력기기공학회 논문집
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• 제11권1호
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• pp.74-78
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• 2015

Nuclear power plant steam generator that is one of the main component has several thousands of thin tubes. And the steam generator tube is subject to damage because of the severe operation conditions such as the high temperature and pressure. Therefore periodic inspections are conducted to ensure the integrity of steam generator component. Hanul unit 3 also has been inspected in accordance with in-service inspection program and is scheduled to be replaced for exceeding the plugging rate which was recommended by manufacturer. During the steam generator replacement activity, we found several clustered porosity on inner surface of main feed water pipe. Additionally crack-like indications were found at weld interface between base material and weld of main feed water pipe. This paper describes the field experience and visual testing results for inner surface of main feed water pipes. The destructive test result had shown that these indications were porosities which were caused by manufacturing process not by operation service.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.187-192
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• 2006

Helicopter noise has been considered as one of major design factors like a performance and safety since the public acceptance, comfortability and stealth aspects were important for customers. According to the airworthiness regulation, the noise levels in throe different flight conditions shall comply with the specific limits. Main and tail rotors noise is most dominant in far field due to the low and mid range frequency characteristics. It is an air-born noise so That the accurate aerodynamic data is necessary for the accurate noise prediction. In KARI, low noise main and tail rotors as well as analysis codes have been developed since 2000. The approach for low noise main rotor is a kind of tip modifications, so called twin vortices tip to reduce the BVI noise. Analysis results show the 9.3dB reduction in terms of pseudo EPNL. The uneven spacing concept is applied for low noise tail rotor. Three or four decibel noise reduction is achieved by new optimized uneven spacing. Rotor noise and aerodynamic prediction codes have been improved also.

• 한국기계가공학회지
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• 제17권1호
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• pp.144-152
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• 2018

The cleanability of machine parts is becoming increasingly important in the industrial field. In particular, cleanability is the most important factor in hydraulic products. The burr and chips are dominant factors of cleanability. If the burrs are not removed completely before the beginning of the machining stage, this will cause many problems, such as scratches and operation failure. Due to the complexity of the valve body itself, it is very difficult to use common deburring tools. In this study, a brush-like deburring tool was suggested and verified as a proper tool for removing the burrs and forming a proper edge shape through a real experiment. Various kinds of brush materials and process conditions were tested for proper deburring of the valve body. It was shown that the suggested method was successful for valve body deburring.