• 한국연소학회지
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• 제13권3호
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• pp.33-40
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• 2008

Two- and Three- dimensional numerical simulations are carried out to understand the combustion characteristics of LNG-fueled gas turbine combustor for power generation using imported and domestic natural gases. Reacting flow characteristics of the swirl stabilized natural gas combustor were understood from the numerical results with the flow conditions selected from the gas turbine operation data. The thermal influences of different natural gases were very small and the fuel composition and flow rate were considered to be tuned well. The flow structures of the recirculation and combustion region was understood from the comparison of the two- and three-dimensional results. The complexity of the three-dimensional swirl flows inside the gas turbine combustor with multiple swirlers was understood those resulting from the interactions of the stage and pilot burners.

• 한국초전도ㆍ저온공학회논문지
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• 제4권1호
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• pp.140-144
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• 2002

A free piston and free displacer (FPFD) Stirling cryocooler has been widely used for the cooling infrared and cryo-sensor. The thermodynamic performance of the free piston and free displacer type (FPFD) Stirling cryocooler is highly dependent on the operating frequency of the linear compressor and the natural frequency of the displacer. In this study, to find optimal relation between operating and natural frequency of the displacer the dynamic characteristics of the displacer in the expansion space of the Stirling cooler was investigated by experiment. The experimental results show that the Stifling cryocooler has maximum cooling capacity at the operating frequency of about 0.8 times of the natural frequency of displacer. Therefore the operating frequency of the Stirring cryocooler should be determined by natural frequency of the linear compressor and displacer.

• 대한가정학회지
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• 제49권8호
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• pp.13-24
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• 2011

This paper purports to find the characteristics of blue costumes as expressed in modern fashion. As such, we made an empirical analysis, using 436 works from 2006 S/S through 2010 F/W collections. Result indicated that modernness was emphasized by applying a minimum expressive technique to items of a simple form, and an image of simplicity was emphasized by placing focus on the rational color image of blue. Second, images of blue, such as trust, stability, and success were expressed as refined elegance through the combination of tight silhouettes, glossy and translucent materials, and indirect exposure. Third, natural image was expressed through natural silhouettes, soft or natural materials, gradation of various tones, and natural motif decorations as well as the color itself. Fourth, dynamic image was expressed by introducing fashion items, mostly worn by men only, to simple and tight forms or through the inspiration of a masculine fashion image. Fifth, abstinent image was expressed by using an image of religious apparel or symbols, covering up the body, minimizing details, and using a dark blue tone.

• Journal of Microbiology and Biotechnology
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• 제17권9호
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• pp.1550-1553
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• 2007

The functional characteristics of a ${\beta}$-cyclodextrin glucanotransferase (CGTase) excreted from alkalophilic Bacillus sp. BL-31 that is highly specific for the intermolecular transglycosylation of bioflavonoids were investigated. The new ${\beta}$-CGTase showed high specificities for glycosyl acceptor bioflavonoids, including naringin, rutin, and hesperidin, and especially naringin. The transglycosylation of naringin into glycosyl naringin was then carried out under the conditions of 80 units of CGTase per gram of maltodextrin, 5 g/l of naringin, 25 g/l of maltodextrin, and 1 mM $Mn^{2+}$ ion at $40^{\circ}C$ for 6 h, resulting in a high conversion yield of 92.1%.

• Environmental Engineering Research
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• 제14권2호
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• pp.95-101
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• 2009

Natural gas is a promising alternative fuel of internal combustion engines. In this paper, the combustion and emission characteristics were investigated on a natural gas engine at two different fuel injection timings during the intake stroke. The results show that fuel injection timing affects combustion processes. The optimum spark timing (MBT) achieving the maximum indicated mean effective pressure (IMEP) is related to fuel injection timing and air fuel ratio. At MBT spark timing, late fuel injection timing delays ignition timing and prolongs combustion duration in most cases. But fuel injection timing has little effect on IMEP at fixed lambdas. The coefficient of variation (COV) of IMEP is dependent on air fuel ratio, throttle positions and fuel injection timings at MBT spark timing. The COV of IMEP increases with lambda in most cases. Late fuel injection timings can reduce the COV of IMEP at part loads. Moreover, engine-out CO and total hydrocarbon (THC) emissions can be reduced at late fuel injection timing.

• 한국소음진동공학회논문집
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• 제14권8호
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• pp.661-667
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• 2004

The characteristics of noise and vibration by a heavy impact source was studied. The triggering method was used for increasing the reliability and stability to measure the level of sound pressure. sound intensity and vibration acceleration. A simple finite element model and a rigid body analysis method were suggested to calculate the natural frequencies of the multi-layer floor system. The results show that the resilient materials decrease the natural frequency of the reinforced concrete slab, make a resonance with dominant driving frequency in the low frequency region, and increase the vibration and noise level. A simple finite element model and rigid body models was suggested to calculate the natural frequencies of the floor systems.

• 한국환경복원기술학회지
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• 제8권1호
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• pp.1-9
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• 2005

This study was conducted to establish a management plan for the Sangrim Woodlands restoration by analyzing the site characteristics of the Sangrim Woodlands Natural Monument(Natural Monument 154) in Hamyang-Gun, Gyoungsangnam-Do, Korea. Site preparation to enhance soil aeration should be applied because soil bulk density in all study sites was higher than soil compaction of natural forest soil area. Herbaceous plants could be introduced to hard soil strength for restoration of areas compacted by visitors. Also, visitors around forest areas should be restricted to enhance natural soil restoration. Soil pH in the Sangrim Woodlands was between 4.18 and 4.90. The values were lower than pH 5.34 of Korean forest soil originated from metamorphic parent materials. Lime fertilizer could be applied to reduce soil acidification in the woodlands. Short and long-term management plans such as periodical fertilizations to improve plant growth should be established to restore the Sangrim Woodlands which have high soil compaction, low soil pH and organic matter content.

• 한국기계연구소 소보
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• 통권19호
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• pp.5-14
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• 1989

Analytical and experimental studies are performed to identify the longitudinal vibration characteristics of elevator system such as the natural frequencies, and the magnification factor at resonance. In the analytical study, a computer program is developed to analyze the vibration characteristics of elevator with varing rope length of elevtor, stiffenss of thimble rod spring, and excitation frequency. The shorter rope length and the stiffer thimble rod spring make the natural frequencies of elevator higer. The resonance at the first natural frequency spreads over the entire travelling range, whereas, that at the second one ranges relatively short, region. The first natural frequencies of the Gald-Star Twin Building and the Korea Trading Center Building obtained by the experiment are overall in good agreement with the analysis result..

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.683-688
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• 2003

Vibration characteristics of a fuel rod to be used in KALIMER(Korean Advanced LIquid MEtal Reactor) have been estimated through 3-dimensional finite element analysis and verified by experiment. The fundamental natural frequencies are found to be 6㎐ in air and 2.5㎐ in water. respectively. It has been found that in-water natural frequencies of the fuel rod are lower than in-air ones due to the added mass effect of the fluid filled inside the outer cylinder and they further decreases as the gap between the fuel rod and the outer cylinder increases, namely the added mass effect increases as the gap increases(maximum 54%). It has been also shown that the mass of the wire wrap axially coiled around the fuel rod do not affect the natural frequencies.

• Structural Engineering and Mechanics
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• 제33권6호
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• pp.747-763
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• 2009

In this work, the linear vibration characteristics of $90^{\circ}$ pipe bends and their cylindrical and toroidal shell components are studied. The finite element method, based on shear-deformation shell elements, is used to carry out a vibration analysis of metallic multiple $90^{\circ}$ mitred pipe bends. Single, double, and triple mitred bends are considered, as well as a smooth bend. Sample natural frequencies and mode shapes are given. To validate the procedure, comparison of the natural frequencies is made with existing results for cylindrical and toroidal shells. The influence of the multiplicity of the bend, the boundary conditions, and the various geometric parameters on the natural frequency is described. The differential quadrature method, based on classical shell theory, is used to study the vibration of components of these bends. Regression formulas are derived for cylindrical shells (straight pipes) with one or two oblique edges, and for sectorial toroidal shells (curved pipes, pipe elbows). Two types of support are considered for each case. The results given provide information about the vibration characteristics of pipe bends over a wide range of the geometric parameters.