• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.4
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• pp.555-560
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• 2000

This paper describes the macroscopic behavior and atomization characteristics of the high-pressure gasoline injector in direct-injection gasoline engine. The global spray behavior of fuel injector was visualized by shadowgraph technique. The atomization characteristics of gasoline spray such as mean diameter and mean velocity of droplet were measured by the phase Doppler particle analyzer system. In order to obtain the influence of fuel injection pressure, the macroscopic visualization and experiment of particle measurement on the fuel spray were investigated at 3,5 and 7 MPa of injection pressure under different surrounding pressure in the spray chamber. The results of this work show that the fuel injection pressure of gasoline injector in GDl engine has influence upon the mean droplet diameter, mean velocity of spray droplet, the spray tip penetration, and spray width under the elevated ambient pressure.

• Journal of ILASS-Korea
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• v.11 no.3
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• pp.168-175
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• 2006

The static pressure distribution and flow characteristics inside the high-pressure swirl spray were investigated by measuring the static pressure inside the spray and applying the computational fluid dynamics (CFD). The static pressure difference between inner and outer part of spray was measured at different axial locations and operating conditions using a piezo-resislive pressure transducer. To obtain the qualitative value of swirl motion at different operating conditions, the spray impact-pressure at the nozzle exit was measured using a piezo-electric pressure transducer, and the flow angle was measured using a microscopic imaging system. The flow characteristics inside the high pressure swirl spray was simulated by the 1-phase 3-dimensional CFD model. The effect of pressure alternations on spray development was discussed with macroscopic spray images and a mathematical liquid film model. The results showed that the static pressure drop is observed inside the swirl spray as a result of the dragged air motion and the centrifugal force of the air. The recirculation vortex inside the spray was also observed inside the swirl spray as a result of the adverse pressure gradient along the axial locations. The results of analytical liquid film model and macroscopic spray images showed that the static pressure structure is one of the main parameters affecting the swirl spray development.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.3
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• pp.28-36
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• 2000

Spray characteristics of diesel fuel injection is one of the most important factors in diesel combustion and pollutant emissions especially in HSDI (High Speed Direct Injection) diesel engines where the interval between the onset of combustion and the evaporation of atomized fuel is relatively short, An investigation into various spray characteristics from different holes of VCO(Valve Covered Orifice) nozzles was performed and its results were compared to standard sac nozzle. The global characteristics of spray, including spray angle, spray tip penetration, and spray pattern were measured from the spray images which were frozen by an instantaneous photography with a spark light source. For better understanding of spray behavior, SMD of the fuel sprays from multi hole nozzles were measured with back light imaging while the sprays from the other holes are covered by a purpose-built nozzle cap. The investigation manifestly reveals the different spray patterns at the beginning of injection produced by VCO nozzles can be identified as three distinct types with their own macroscopic and microscopic characteristics, while macroscopic non-uniformity disappears at 0.9∼1.0ms from the start of injection.

• The Journal of Korean Medicine
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• v.35 no.4
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• pp.83-97
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• 2014

Objectives: This study aimed for establishing the discriminative criteria for Aucklandiae Radix, Inulae Radix, Vladimiriae Radix and Aristolochiae Radix, which can be confused as 'Mokhyang', because of similar appearances and synonyms. Methods: Morphological characteristics of dried herbal medicines were compared by macroscopic observation. To examine microscopic features of 'Mokhyang', paraffin embedding and the staining by using Ju's method were conducted. Physicochemical experiments were performed using HPLC analysis and antioxidant assay. Results: The types of stem, phyllotaxy and leaf shape were chosen as macroscopic criteria and the size, oil spots, color and root top as well as phloem and central cylinder were compared using microscopic features. The HPLC results showed different amounts of costunolide and dehydrocostuslactone among Aucklandiae Radix, Inulae Radix and Vladimiriae Radix. However, Aristolochiae Radix only contained aristolochic acid. The antioxidant assays also showed that Vladimiriae Radix exhibited strongest antioxidant activity followed by Aucklandiae Radix, Inulae Radix and Aristolochiae Radix. Conclusions: These results demonstrate that macroscopic, microscopic and physicochemical methods would be useful tools for the discrimination of 4 kinds of 'Mokhyang'.

• Journal of ILASS-Korea
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• v.17 no.3
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• pp.121-127
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• 2012

The study is to investigate the mixing stability, fuel properties, and macroscopic spray characteristics of diesel-gasoline blended fuels in a common-rail injection system of a diesel engine. The test fuels were mixed diesel with gasoline fuel, which were based volume fraction of gasoline from 0 to 100% in 20% intervals. In order to analyze the blended effect of gasoline to diesel fuel, the properties of test fuels such as density, viscosity, and surface tension were measured. In addition, the spray behavior characteristics were studied by investigating the spray tip penetration and spray angle using a spray images through a spray visualization system. It was revealed that the density, kinematic viscosity and surface tension of diesel-gasoline blending fuels were decreased with the increase of gasoline fuel. The injection quantity of test fuels were almost similar level at short energizing duration condition. On the other hand, the increase of energizing duration shows the decrease of injection quantity compared to short energizing duration. The test blending fuels have similar growth in Spray tip penetration and Spray cone angle.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.143-148
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• 2012

This study is an investigation on macroscopic spray behavior of nonimpinging-type injector equipped on the hydrazine thruster under development. An electron microscope is employed for the acceptance examination of injector orifice. Initial performance characteristics and spray behavior of injector are observed through the instantaneous spray images which are captured by high speed camera and Schlieren method with varying injection pressures. The injector performance is scrutinized by the velocity along with penetration length of spray and categorized by dimensionless parameters. It is confirmed that there exist varying characteristics related to the spray breakup caused by fabrication errors of injector-orifices. Unexpected spray behavior, which needs to be reexamined, is grasped at specific pressure level, as well.

• Composites Research
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• v.15 no.5
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• pp.44-52
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• 2002

To study numerically the mechanical behaviors of advanced composite materials considering the microscopic phenomena as well as the macroscopic properties and behaviors, a multi-scale modeling and analysis by the mathematical homogenization method with the help of the finite element method(FEM) are reviewed. The hierarchical modeling strategy and the formulation are briefly described first to give some idea of the multi-scale framework. The latter half of this article focuses on the verification of the multi-scale analysis by the homogenization method in its applications to real advanced materials. The first example is the verification of the predicted macroscopic(homogenized) properties based on the microstructure of porous ceramics. In spite of the complexity of the random microstructure, the error between the predicted and the measured values was only 1%. Next, two applications to the process simulation of fiber reinforced polymer matrix composites are presented. The permeability characteristics are evaluated for sheared weave fabrics for resin transfer molding(RTM) simulation, and the thermoforming of FRTP sheet is analyzed considering the large deformation of the knit structure during the deep-draw forming was verified by comparison with the experimental results.

• Structural Engineering and Mechanics
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• v.7 no.6
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• pp.601-614
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• 1999

The mechanical behaviours of the structure made from composite materials or the structure with periodic configurations depend not only on the macroscopic conditions of structure, but also on the detailed configurations. The Two-Scale Analysis (TSA) method for these structures, which couples the macroscopic characteristics of structure with its detailed configurations, is configurations, is presented for 2 or 3 dimensional case in this paper. And the finite element algorithms based on TSA are developed, and some results of numerical experiments are given. They show that TSA with its finite element algorithms is more effective.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.3019-3025
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• 2008

An experimental study was performed to assess the effect of diesel and JP-8 aviation fuel on the spray characteristics, performance and emissions in a single cylinder optical diesel engine. Both fuels were injected via an 8-hole solenoid-driven injector in a common-rail injection system. For better understanding of spray development, the macroscopic images were captured with high speed camera, offered evidences for the results of performance and emissions. From macroscopic spray images, the spray tip penetration of JP-8 shorter than that of diesel while spray angle of JP-8 was wider than that of diesel. It indicates that the vaporization of JP-8 is superior to that of diesel. The lower cetane number of JP-8 resulted in increased portion of premixed combustion. The IMEP with JP-8 is lower than that of diesel-fueled engine. Especially, using JP-8 has a potential for reducing soot.

• Journal of The Korean Association For Science Education
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• v.27 no.4
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• pp.337-345
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• 2007

The purposes of this study are to investigate and compare the characteristics of classification criteria of secondary school students and science teachers in relation to the three statesof matter. For this research, 76 middle school students in the7th grade who studied microscopic viewpoints about classifying the state of matter for the first time, 69 high school students in the 12th grade who studied Chemistry I and IIcourses successfully, and 130 secondary school science teachers, through a questionnaire. As a result, while having learned the three states of matter in the microscopic viewpoints, the majority of middle school students showed a high percentage of classification in the macroscopic viewpoints. For high school students, their percentage of classification included highmicroscopic viewpoints about solid and gas, the percentage of classification included macroscopic viewpoints about liquid state as alsohigh. The secondary school teachers gave answers in the macroscopic viewpoints and microscopic viewpoints equally, but their answers were just representation of the viewpoints list without the meaningful connection of the two type of viewpoints. To solve these problems, It is necessary to form connective change from the macroscopic viewpoints to the microscopic viewpoints about the criteria for classifying the States of Matter and various educational efforts.