• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.6
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• pp.519-523
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• 2008

Poisson's ratio is one of elastic constants of elastic solids. However, it has not attracted attention due to its narrow range and difficult measurement. Transverse wave velocity as well as longitudinal wave velocity should be measured for nondestructive measurement of Poisson's ratio. Hard couplant for transverse wave prevents transducer from scanning over specimen. In the present work, a novel measurement of Poisson's ratio distribution was proposed. Immersion method was employed for the scanning over the specimen. Echo signals of normal beam longitudinal wave were collected. Transverse wave modes generated by mode conversion were identified. From transit time of longitudinal and transverse waves, Poisson's ratio can be determined without information of specimen thickness. This technique was demonstrated for aluminum and steel specimens.

• Korean Journal of Mathematics
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• v.18 no.4
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• pp.409-424
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• 2010

We observed the symptoms that occur to students who dislike mathematics when they study mathematics and the data that mathematics is related to foreign language. This study investigated the relation between mathematics and foreign language. Continuous immersion aids not only in acquiring language but also in learning mathematics. For continuous immersion, it is essential to organize small class. We organized small class and compared large class with small class about how the relation between mathematics and language appears in achievement, rate of presence, rate of submission of report, and attitude and enthusiasm. Based on the result, we try to find out the way to increase understanding mathematics and level up the achievements.

• Advances in aircraft and spacecraft science
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• v.2 no.3
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• pp.249-261
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• 2015

The mechanical characterization of composite materials is nowadays a major interest due to their increasing use in the aeronautic industry. The design of most of these materials is based on their stiffness, which is mainly obtained by means of tensile tests with strain gauge measurement. For thin laminated composites, this classical method requires adequate samples with specific orientation and does not provide all the independent elastic constants. Regarding ultrasonic characterization, especially immersion technique, only one specimen is needed and the entire determination of the stiffness tensor is possible. This paper presents a study of different methods to determine the mechanical properties of transversely isotropic carbon fibre composite materials (gauge and correlation strain measurement during tensile tests, ultrasonic immersion technique). Results are compared to ISO standards and manufacturer data to evaluate the accuracy of these techniques.

• Journal of the Optical Society of Korea
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• v.15 no.1
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• pp.78-81
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• 2011

We demonstrate a high-spatial-resolution imaging and spectroscopy tool using a solid immersion lens (SIL), a hemispherical lens made of high refractive index glass (n ~2). Photoluminescence (PL) images of single CdSe nanocrystals confirm a numerical aperture enhancement factor of ~2, close to the refractive index of the SIL. In particular, a bare-eye observation of PL signals emitted by single nanocrystals with ${\sim}10\;{\mu}m^{-2}$ densities was possible over an ${\sim}30\;{\mu}m$ diameter region. In addition, the PL spectra of single CdSe nanocrystals were successfully measured at room temperature. Thus, this SIL microscope ensures a simple but powerful method for nanostructure spectroscopy.

• Korean Journal of Food Science and Technology
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• v.21 no.6
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• pp.735-741
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• 1989

For the accurate prediction of freezing time, probably the most difficult factor to measure and major error source is the surface heat transfer coefficient. In this work, surface heat transfer coefficient were determined for still air freezing and immersion freezing methods by theory of the transient temperature method and confirmed by using a modification of plank's equation to predict the freezing time of ground lean beef. The results showed the cooling rate of immersion freezing was about 11 times faster than that of still air freezing method. A comparison of surface heat transfer coefficient of copper plate and ground lean beef resulted an difference of 25-30% because the food sample surface is not smooth as copper plate. Also, when h-values measured by ground lean beef were applicated to modified model, the accuracy of its results is very high as difference of about 8%.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.20 no.3
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• pp.297-306
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• 2022

The acoustic emission (AE) is proposed as a feasible method for the real-time monitoring of the structural damage evolution in concrete materials that are typically used in the storage of nuclear wastes. However, the characteristics of AE signals emitted from concrete structures subjected to various environmental conditions are poorly identified. Therefore, this study examines the AE characteristics of the concrete structures during uniaxial compression, where the storage temperature and immersion conditions of the concrete specimens varied from 15℃ to 75℃ and from completely dry to water-immersion, respectively. Compared with the dry specimens, the water-immersed specimens exhibited significantly reduced uniaxial compressive strengths by approximately 26%, total AE energy by approximately 90%, and max RA value by approximately 70%. As the treatment temperature increased, the strength and AE parameters, such as AE count, AE energy, and RA value, of the dry specimens increased; however, the temperature effect was only minimal for the immersed specimens. This study suggests that the AE technique can capture the mechanical damage evolution of concrete materials, but their AE characteristics can vary with respect to the storage conditions.

• Journal of Broadcast Engineering
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• v.26 no.5
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• pp.500-507
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• 2021

The virtual reality industry has an opportunity to take another leap forward with the surge in demand for non-face-to-face content and interest in the metaverse after Covid-19. Therefore, in order to popularize virtual reality content along with this trend, high-quality content production and storytelling research suitable for the characteristics of virtual reality should be continuously conducted. In order for content to which virtual reality characteristics are applied to be effectively produced through user feedback, a quantitative index that can evaluate the content is needed. In this study, the process of viewing virtual reality contents was analyzed and head movement was set as a quantitative indicator. Afterwards, the experimenter watched five animations and analyzed the correlation between recorded head movement information and immersion. As a result of the analysis, high immersion was shown when the head movement speed was relatively slow, and it was found that the head movement speed can be used significantly as an index indicating the degree of content immersion. The result derived in this way can be used as a quantitative indicator that can verify the validity of the storytelling method applied after the prototype is produced when the creator creates virtual reality content. This method can improve the quality of content by quickly identifying the problems of the proposed storytelling method and suggesting a better method. This study aims to contribute to the production of high-quality virtual reality content and the popularization of virtual reality content as a basic research to analyze immersion based on the quantitative indicator of head movement speed.

• Journal of the Korean Wood Science and Technology
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• v.26 no.1
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• pp.97-105
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• 1998

This study examined the combined using effects of urea-formaldehyde (UF) resin and emulsifiable methylene diphyenyl diisocyanate (EMDI) resin to overcome performance limit of three-layer particleboards commonly made by UF resin. Two adhesive adding methods were applied with three types of resin combination system to each layer of particleboards. The one was simultaneously spreading method with emulsified compound resin (UF and EMDI) while the other was separately spreading method with unemulsified EMDI resin after UF resin spreading. The performance of particleboards bonded with 2% EMDI resin to the inner layers(IL) were similar to that of controls bonded with 8% UF resin. In the case of the emulsified compound resin application to the all layers of particleboards, there were marked reinforcing effects of EMDI resin, although a small amount of EMDI resin was mixed with UF resin. Especially bending MOR after 24 hours cold water-immersion and thickness swelling after 2 hours hot water-immersion of compound resin-bonded particleboards were remarkably different from those of pure UF resin-bonded particleboards. It was found that separately spreading method with unemulsified EMDI resin was more effective than simultaneously spreading method with emulsified compound resin to sustain the internal bond strength of particleboards after 24 hours cold water-immersion. In the resin combination systems to outer layers/inner layers of particleboards, water resistance and strength properties were superior in order of UF+EMDI/UF+EMDI > UF/UF+EMDI > UF/UF. And water resistance of particleboards was greatly dependent upon EMDI resin level in any adhesive adding method.

• Journal of Sasang Constitutional Medicine
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• v.10 no.1
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• pp.143-160
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• 1998

PURPOSE This studied the biomechanical body segment parameters of Korean adults with reference to Sasang Constitutional Medicine(SCM). We anlyzed the characteristics of Sasang constitution through Body Measurement, Immersion Method, and Reaction Board Method. SUBJECT Subjects were 72 persons. There were made 49 and Female 23. Mean age was . And There were Taeumin 30, Soyangin 17, and Soeumin 25. METHOD The items of Body Measurement were 51. Limbs were measured right side. Volume was gained with Immersion Method and Weight was calculated with the density equation for limbs from Drills and Contini. Center of Mass was gained with Reaction Board Method. RESULT 1. In Body Measurement there were the significant differences with each constitution of man's circumference. 2. In Volume there were the significant differences between Taeumin and Soeumin in mand. And the volume rate of head and neck, hand, and foot was the lowest in Taeumin, but the highest in Soeumin. 3. In center of mass Soyangin was higher than others.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.1
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• pp.146-153
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• 1997

An experiment was conducted to figure out the atomization characteristics of a highly viscous biodiesel fuel with rice-barn oil applying and ultrasonic energy into it. A spray simulator for the droplet atomization, an ultrasonic system, and six different nozzles(3 pintle-type nozzles and 3 single hole-type nozzles) were made. To investigate effects of ultrasonic energy in a highly viscous liquid fuel, an immersion liquid method was used as a measurement method on droplet size distributions. It was found that the ultrasonic energy was effective for the atomization improvement of the rice-bran oil as a highly viscous biodiesel fuel and the factor나 such as the nozzle opening pressure, pin-edge angles, hole diameters, and collection distances affected the atomization of spray droplets.