• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.26 no.2
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• pp.108-120
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• 2022

We considered qualitative behaviour of the generalization of Einstein's model of Brownian motion when the key parameter of the time interval of free jump degenerates. Fluids will be characterised by number of particles per unit volume (density of fluid) at point of observation. Degeneration of the phenomenon manifests in two scenarios: a) flow of the fluid, which is highly dispersing like a non-dense gas and b) flow of fluid far away from the source of flow, when the velocity of the flow is incomparably smaller than the gradient of the density. First, we will show that both types of flows can be modeled using the Einstein paradigm. We will investigate the question: What features will particle flow exhibit if the time interval of the free jump is inverse proportional to the density and its gradient ? We will show that in this scenario, the flow exhibits localization property, namely: if at some moment of time t₀ in the region, the gradient of the density or density itself is equal to zero, then for some T during time interval [t₀, t₀ + T] there is no flow in the region. This directly links to Barenblatt's finite speed of propagation property for the degenerate equation. The method of the proof is very different from Barenblatt's method and based on the application of Ladyzhenskaya - De Giorgi iterative scheme and Vespri - Tedeev technique. From PDE point of view it assumed that solution exists in appropriate Sobolev type of space.

• Journal of Korean Medical classics
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• v.36 no.3
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• pp.27-54
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• 2023

Objectives : To determine the background against which Zhishi has been applied to treat Pi pattern, through examination of changes in Pi pattern treatments in a historical context. Methods : The properties and nature of Zhishi as written in multiple bencao texts were analyzed. In addition, understanding of the Pi pattern, the changes in its treatment were examined diachronically based on opinions of Zhang Zhongjing, Zhugong, and Li Dongyuan. Examples of Zhishi application in Pi pattern treating formulas were collected and their mechanisms analyzed. Results : Zhishi is strongly effective in relieving accumulation and stagnation, due to its properties of dispersing and lowering. The early view of contrasting Pi with Jiexiong shifted to viewing the Pi pattern as an inner damage, from the perspective of rising and lowering of the Qi mechanism based on the Spleen and Stomach. As a result, Zhishi became a key ingredient in the treatment of the Pi pattern. Conclusions : As the perspective of seeing Pi as one end of the Yin-Yang coupling with Jiexiong from the Shanghanlun shifted to seeing it as a problem of Qi mechanism of the Spleen and Stomach, Zhishi became a key ingredient in the formulas to treat Pi pattern. The complexity of Zhishi's direction made it appropriate to treat the changed Pi pattern.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.40.4-40.4
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• 2020

Kyung Hee university invented the Transformable Reflective Telescope (TRT) for optical experiment and education. The TRT kit can transform into three optical configurations from Newtonian to Cassegrain to Gregorian by exchanging the secondary mirror. We designed the Ebert-Fastie spectrograph as an extension of the TRT kit. The primary mirror of the TRT kit serves as both collimator and camera lens, and the reflective grating as the dispersing element is placed along the optical axis of the primary mirror. We designed and fabricated the grating holder and the source units using 3D printer. Baffle was also fabricated to suppress the stray light, which was reduced by 83%. The spectrograph can observe the optical wavelength range (4000Å~7000Å). Measured resolving power (R=λ/Δλ) was ~700 with slit width of 0.18mm. The spectrograph is optimized for f/24, and the spectral pixel scale is 0.49Å/pixel with Canon 550D detector. We present the sample spectra of discharged Ne, Ar and Kr gases. The flexible setting and high performance make this spectrograph a useful tool for education and experiment.

• Journal of Sasang Constitutional Medicine
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• v.13 no.3
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• pp.1-7
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• 2001

We analyzed 45 types of herbal medicines for Soyangin, clinically applied in Dongyisoosebowon. In order to discover the standard of herbal classification for the Sasang constitutions, four concepts of Sasang Medicine were applied. These included 'Sadangron(theory of four groups)', 'Seungganggaehap(ascending-descending and gathering-dispersing)', 'Pyorihanyoul(exterior-interior and hot-cold)', and 'Hyungchiaekmi(fragrance, smell, bodily fluid and taste)'. According to these analyzing methods of herbal properties, we have reached the following conclusions: Herbal medicines for 'Soyangin' are characterized by descending energetics that reinforce the Yin Qi. The 'Exterior cold disease' is treated with herbs that descend the "Exterior Yin" in five ways: by releasing exterior, by resolving dampness, by clearing and transforming heat phlegm, by clearing heat, and by settling and calming the spirit. The 'Interior heat disease' is treated with herbs that raise the "Interior Yang" in three ways: by tonifying kidney Yin, by clearing heat, and by clearing heat and purging.

• Advances in nano research
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• v.16 no.1
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• pp.11-26
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• 2024

In this study, free vibration analysis of FG porous spherical cap reinforced by graphene platelets resting on Winkler-type elastic foundation has been surveyed for the first time. Three different types of porosity patterns are considered for the spherical cap whose two types of porosity patterns in the metal matrix are symmetric and the other one is uniform. Besides, five GPL patterns are assumed for dispersing of GPLs in the metal matrix. Tsai-Halpin and extended rule of the mixture are used to determine the Young modulus and mass density of the shell, respectively. Employing 3D FEM elasticity in conjunction with Hamilton's Principle, the governing motion equations of the structure are obtained and solved. The impact of various parameters including porosity coefficient, various porosity distributions in conjunction with different GPL patterns, the weight fraction of graphene Nano fillers, polar angles and stiffness coefficient of elastic foundation on natural frequencies of FG porous spherical cap reinforced by GPLs have been reported for the first time.

• Applied Chemistry for Engineering
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• v.21 no.1
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• pp.46-51
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• 2010

Polyorganosiloxane modified polyurethane (PDMS-PU) polymers were prepared from copolymerization of ${\alpha}$,${\omega}$-hydroxypropyl terminated polyorganosiloxane with isophorone diisocyanate (IPDI), polypropylene glycol (PPG), and 2,2-bis(hydroxymethyl) propionic acid (DMPA). Hydrophobic polyorganosiloxane was introduced in polyurethane main chain as soft segment block unit. The isocyanate groups in PDMS-PU block copolymer was blocked with 2-butanon oxime and obtained PDMS-PU dispersions in water by neutralizing with triethylamine (TEA). The deblocking temperature of PDMS-PU polymer was measured from thermal analysis. The good stability of the PDMS-PU dispersion was obtained by dispersing into water. PDMS-PU prepolymers were prepared with various contents of DMPA under [NCO]/[OH] = 1.12~1.53 equivalent ratio. Increasing DMPA from 7.2, 13.4, and 18.7 mole% in preparation of PDMS-PU polymer, particle sizes were decreased from 156, 100, 65 dnm. Also contact angle and adhesive strength were measured.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.1
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• pp.49-57
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• 2005

[ $MO/Al_2O_3-ZrO_2$ ](M=Ni and Cu) mixed metal oxides were prepared using sol-gel method in order to investigate the applicability to the 2-step thermo-chemical water splitting process and their redox behaviors were studied by temperature programmed reaction(TPR) from room temperature to 900$^{\circ}C$ under 5% $H_2$/Ar for the reduction and $H_2O$/Ar for the oxidation, respectively. From the results, peaks of the reduction and the oxidation on temperature were shifted with the change of crystalline phases due to the addition of $Al_2O_3$ and $ZrO_2$. The intensities of the peaks were also increased with the increase of contents of NiO or CuO that could be considered as active species. In addition, based on the observation of SEM images before and after the redox test, it seemed that $Al_2O_3-ZrO_2$ added prevented high temperature sintering of active metal components such as Ni (or Cu) on the surface and played a role of dispersing the active species homogeneously in solid solution of mixed oxides.

• Journal of the Korean Home Economics Association
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• v.46 no.6
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• pp.13-19
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• 2008

In this paper, the dyeing ability of the volcanic ash dyeing on cotton knitted fabrics were investigated. Acrylic copolymer was used to improve the depth of fabric color in the dyeing process. K/S values of dyed fabrics were measured to examine the dyeing properties. Two different classes of dyeing process were tested; (1) volcanic ash dyeing after pretreatment and (2) simultaneous co-treatment with volcanic ash and acrylic copolymer. In the first process, the effects of parameters such as the concentration of volcanic ash, concentration of Na2S04, dyeing time, dyeing temperature and pH of dyebath were noted. In the second process, the effects of parameters such as concentration of acrylic copolymer, dyeing time and temperature, and drying temperature were noted. Experimental results showed that the co-treatment of acrylic copolymer improved the dyeing properties of cotton knitted fabrics with volcanic ash. For the first dyeing experiment, concentration of dispersing agent was 0.1%, concentration of volcanic ash was 4%, treatment time was 20minutes, concentration of $Na_2SO_4$ was 2%, treatment temperature was $60^{\circ}C$ and treatment pH of dyebath was neutral. In the second dyeing experiment, concentration of acrylic copolymer was 2%, treatment temperature was $80^{\circ}C$, treatment time was 40 minutes, and treatment drying temperature was $150^{\circ}C$.

• Korean Journal of Materials Research
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• v.12 no.11
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• pp.840-844
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• 2002

A spherical $BaMgAl_{10}$ $O_{17}$ :Eu phosphor has been synthesized by a multi-step precipitation route. In order to successfully synthesize the phosphor with spherical shape, the hydrated-alumina particles should be controlled for spherical shape. In this process, the hydroxypropyl cellulose (HPC) was used as a dispersing reagent. This reagent plays an important role in that the particles were controlled to have the uniform size of sub-micron. The final product prepared by the multi-step precipitation method maintained spherical shape with uniform size of 0.4$\mu\textrm{m}$. It can be seen in X-ray diffraction patterns, formation of the single phase of $BaMgAl_{10}$ $O_{17}$ :Eu phosphor prepared by the multi-step precipitation method at $1350^{\circ}C$. Also, the emission spectra of spherical $BaMgAl_{O}$ $10_{17}$ :Eu phosphor in the present case was compared with those of commercially-available blue phosphor under VUV (Vacuum Ultra Violet) excitation. The luminescence process of the $BaMgAl_{10}$ $O_{17}$ :Eu phosphor is characterized by the $4f^{6}$$5d^1$longrightarrow4f$^{7}$ transition (blue) of the $Eu^{2+}$ ion acting as an activating center and the maximum luminescence intensity was obtained by reduction treatment at 145$0^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.49 no.4
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• pp.333-336
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• 2012

The study to give electrical conductivity by dispersing carbon nanotubes (CNT) into silicon nitride ($Si_3N_4$) ceramics has been carried out in recent years. However, the density and the strength of $Si_3N_4$ ceramics were degraded and CNTs disappeared after firing at high temperatures because CNTs prevent $Si_3N_4$ from densification and there is a possibility that CNTs react with $Si_3N_4$ or $SiO_2$. In order to suppress the reaction and the disappearance of CNTs, lower temperature densification is needed. In this study, $HfO_2$ and $TiO_2$ was added to $Si_3N_4-Y_2O_3-Al_2O_3$-AlN system to fabricate CNT-dispersed $Si_3N_4$ ceramics at lower temperatures. $HfO_2$ promotes the densification of $Si_3N_4$ and prevents CNT from disappearance. As a result, the sample by adding $HfO_2$ and $TiO_2$ fired at lower temperatures showed higher electrical conductivity and higher bending strength. It was also shown that the mechanical and electrical properties depended on the quantity of the added CNTs.