• Journal of the Korean Chemical Society
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• v.62 no.3
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• pp.243-252
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• 2018

In this study, we compared 8th graders' macroscopic and microscopic conceptions related to the properties of substances. A test for the basic particle concept and a test for the macroscopic and microscopic concepts of melting point, solubility, and density were developed and administered to 371 students. Their responses were classified into 4 categories on the bases of their understanding of the macroscopic and microscopic concepts. The proportions and characteristics of each category were also analyzed. The analyses of the results revealed that the students who understood the macroscopic concepts had various misconceptions at the microscopic level. Many students had difficulty in understanding not only microscopic concepts but macroscopic concepts. The microscopic responses of the students who did not understand the macroscopic concepts hardly corresponded with their macroscopic level responses. The students who responded correctly to the test for the basic particle concept also had difficulty in understanding the concept of the properties of substances. When they understood the macroscopic concepts, the proportions of the students who understood the microscopic concepts were high. On the bases of the results, educational implications for effective teaching and learning of concepts related to the properties of substances and for improving the future national curricular are discussed.

• Structural Engineering and Mechanics
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• v.19 no.5
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• pp.519-533
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• 2005

The numerical simulations on the influence of mesoscopic structures on the macroscopic strength and fracture characteristics are carried out based on that the concrete is assumed to be a three-phase composite composed of matrix (mortar), aggregate and bond between them by using a numerical code named MFPA. The finite element program is employed as the basic stress analysis tool when the elastic damage mechanics is used to describe the constitutive law of meso-level element and the maximum tensile strain criterion and Mohr-Coulomb criterion are utilized as damage threshold. It can be found from the numerical results that the bond between matrix and aggregate has a significant effect on the macroscopic mechanical performance of concrete.

• Biomolecules & Therapeutics
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• v.7 no.4
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• pp.347-353
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• 1999

Osteoarthrosis was induced in rabbit knees through resecton of anterior cruciate ligament. Sodium hyaluronate (1%) was administerated into articular space at the dose levels of 0.1 mg/kg once a week using 1ml sylinge and 26G needle for test groups. Saline was administrated for control groups. After 6 and 12 weeks, animals were sacrificed to conduct macroscopic observation and histopathologic examination. The articular lesions were evaluated and test groups were compared with control groups. No significant differencies were showed between test groups and control groups at macroscopic observation in both 6- and 12- week groups. In histopathologic examination, control groups showed higher osteoarthrosis than test groups. The articular surfaces of control groups showed fibrillation, denudation, pannus formation and hypocellularity. The articular surfaces of test groups showed fibrillaton and hypercellularity. These indicate that sodium hyaluronate has inhibitory effects on osteoarthrosis at least in rabbit and could be used for treatment of osteoarthrosis.

• The Journal of Pediatrics of Korean Medicine
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• v.31 no.2
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• pp.57-63
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• 2017

Objectives The purpose of this case study is to report the effect of Yukmijihwangtang-gamibang on recurrent hematuria in childhood. Methods The subject was a male child with macroscopic hematuria. This patient was only treated with oriental herbal medicine. The improvement was observed by subjective symptoms and routine urinalysis. Results After the treatment with Yukmijihwangtang-gamibang, the symptoms of macroscopic hematuria were relieved. The occult blood test was negative as well. The number of red blood cells in urine was within the normal range. He was less tired but hematuria did not recur even after intense exercise. Conclusions This study showed that Korean medical treatment with using herbal medicine such as Yukmijihwangtanggamibang can be an effective treatment option for asymptomatic macroscopic hematuria.

• Journal of Mechanical Science and Technology
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• v.18 no.7
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• pp.1222-1235
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• 2004

This study examines the influence of geometry on the internal flow and macroscopic behavior of the spray in Diesel nozzles. For this investigation, two bi-orifice nozzles were employed: one cylindrical and one conical. The first step is to use a non-destructive characterization method which is based on the production of silicone moulds so that the precise internal geometry of the two nozzles can be measured. At this stage the nozzles have been characterized dimensionally and therefore the internal flow can be studied using CFD calculations. The results gained from this experiment make it possible also to ascertain the critical cavitation conditions. Once the critical cavitation conditions have been identified, the macroscopic parameters of the spray can be studied in both cavitating and non-cavitating conditions using a test rig pressurized with nitrogen and with the help of a image acquisition system and image processing software. Consequently, research can be carried out to determine the influence that cavitation has on macroscopic spray behavior. From the point of view of the spray macroscopic behavior, the main conclusion of the paper is that cavitation leads to an increment of the spray cone angle. On the other hand, from the point of view of the internal flow, the hole outlet velocity increases when cavitation appears. This phenomenon can be explained by the reduction in the cross section of the liquid phase in the outlet section of the hole.

• Journal of Drive and Control
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• v.16 no.2
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• pp.80-90
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• 2019

Fuel cell hybrid electric vehicle is an attractive solution to reduce pollutants, such as noise and carbon dioxide emission. This study presents an approach for energy management and control algorithm based on energetic macroscopic representation for a fuel cell hybrid electric vehicle that is powered by proton exchange membrane fuel cell, battery and supercapacitor. First, the detailed model of the fuel cell hybrid electric vehicle, including fuel cell, battery, supercapacitor, DC-DC converters and powertrain system, are built on the energetic macroscopic representation. Next, the power management strategy was applied to manage the energy among the three power sources. Moreover, the control scheme that was based on back-stepping sliding mode control and inversed-model control techniques were deduced. Simulation tests that used a worldwide harmonized light vehicle test procedure standard driving cycle showed the effectiveness of the proposed control method.

• Tribology and Lubricants
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• v.5 no.1
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• pp.28-35
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• 1989

The wear tests of ceramic materials in dry rolling contact were carried out at room temperature to investigate their macroscopic wear characteristics. Both point contact and line cootact were adapted in the wear tests of them. Ceramic materials used in these tests were silicon nitride, silicon carbide, cermet of TiN and TiC, titania, and alumina. The wear test of the bearing steel was carried out to compare to the wear test results of the ceramic materials. The results showed that the wear rate of silicon nitride was smaller than any other ceramic materials and bearing steel. In the steady wear, the wear volume of ceramic materials increases linearly with the rolling distance. It was also found from the experimental results that fracture toughness and surface roughness dominate the wear process of ceramic materials in dry rolling contact.

• 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.

• Korean Journal of Materials Research
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• v.26 no.7
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• pp.370-375
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• 2016

Tensile tests and creep tests were carried out at high temperatures on an Al-$Al_4C_3$ alloy prepared by mechanical alloying technique. The material contains about 2.0% carbon and 0.9% oxygen in mass percent, and the volume fractions of $Al_4C_3$ and $Al_2O_3$ particles are estimated at 7.4 and 1.4%, respectively, from the chemical composition. Minimum creep rate decreased steeply near two critical stresses, ${\sigma}_{cl}$ (the lower critical stress) and ${\sigma}_{cu}$ (the upper critical stress), with decreasing applied stress at temperatures below 723 K. Instantaneous plastic strain was observed in creep tests above a critical stress, ${\sigma}_{ci}$, at each test temperature. ${\sigma}_{cu}$ and ${\sigma}_{ci}$ were fairly close to the 0.2% proof stress obtained by tensile tests at each test temperature. It is thought that ${\sigma}_{cl}$ and ${\sigma}_{cu}$ correspond to the microscopic yield stress and the macroscopic yield stress, respectively. The lower critical stress corresponds to the local yield stress needed for dislocations to move in the soft region within subgrains. The creep strain in the low stress range below 723 K arises mainly from the local deformation of the soft region. The upper critical stress is equivalent to the macroscopic yield stress necessary for dislocations within subgrains or in subboundaries; this stress can extensively move beyond subboundaries under a stress above the critical point to yield a macroscopic deformation. At higher temperatures above 773 K, the influence of the diffusional creep increases and the stress exponent of the creep rate decreases.

• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.5
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• pp.1-11
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• 2012

In this paper, non-linear analysis was performed for Reinforced Concrete (RC) walls using different macroscopic models subjected to cyclic loading, and the analytical results were compared with previous experimental studies of RC walls. ASCE41-06 (American Society of Civil Engineers) specifies that the hysteresis behaviors of RC walls are different due to the aspect ratio of the walls. For a comparison between analytical and experimental results, a slender wall with an aspect ratio exceeding 3.0 and a squat wall with an aspect ratio of 1.0 were selected among previous research works. For the non-linear analysis, each test specimen was modeled using two different macroscopic methods: the first representing the flexural behavior of the RC wall, and the second considering the diagonal shear in the web of the wall. Through nonlinear analysis of the considered RC walls, the analytical difference of a slender wall was negligible due to the different macroscopic modeling methods. However, the squat wall was significantly affected by the considered components of the modeling method. For an accurate performance evaluation of the RC building with squat walls, it would be reasonable to use a macroscopic model considering diagonal shear.