• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.4
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• pp.131-135
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• 2020

Single crystal phased CaZrO₃ : Eu³⁺ phosphor have been synthesized by skull melting method. The crystal structure, morphology and optical properties of synthesized phosphor were investigated XRD (X-ray diffraction), SEM (scanning electron microscopy), UV (ultraviolet) fluorescence reaction and PL (photo luminescence). The starting materials having chemical composition of CaO: ZrO₂ : Eu₂O₃= 0.962 : 1.013 : 0.025 mol% were charged into a cold crucible. The cold crucible was 120 mm in inner diameter and 150 mm in inner height, and 3 kg of mixed powder (CaO, ZrO₂ and Eu₂O₃) was completely melted within 1 hour at an oscillation frequency of 3.4 MHz, maintained in the molten state for 2 hours, and finally air-cooled. The XRD results show that synthesized phosphor is stabilized in orthorhombic perovskite structure without any impurity phases. The synthesized phosphor could be excited by UV light (254 or 365 nm) and the emission spectra results indicated that bright red luminescence of CaZrO₃ : Eu³⁺ due to magnetic dipole transition ⁵D₀→⁷F₂ at 615 nm was dominant.

• Journal of the Korea Concrete Institute
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• v.26 no.2
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• pp.211-218
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• 2014

In the design of reinforced rectangular concrete beam structure, the minimum amount of flexural reinforcement is required to avoid brittle failure. KCI code is based on concept of ultimate strength and usually used as a model code. But bridge design code enacted by Ministry of land, transportation and maritime affairs in 2012 is based on concept of limit state and similar to Euro code EN 1992-2. This means that the minimum reinforcement presented in both design codes has different origination and safety margin. When rectangular concrete beams with minimum reinforcement are designed according to EN and KCI codes, the amount of minimum reinforcement specified in EN code is only 76% of that in KCI code. This makes the design engineers to be confused. In this study, flexural tests were conducted on nine beams with the two different minimum reinforcement specified in KCI and EN design codes. In results, the measured ratios of nominal strength to crack strength from the test were about 25% greater than those evaluated from the equations presented in KCI and EN codes. The EN beams having only 76% of the minimum reinforcement for the KCI beams were fractured by rupture of steel reinforcement but in ductile manner. It is confirmed that the minimum reinforcement concrete beams designed according to both codes have enough safety margin in flexural capacity and moreover in ductility.

• Journal of The Korean Astronomical Society
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• v.49 no.6
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• pp.261-288
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• 2016

We present the results of simultaneous monitoring observations of $H_2O$ $6_{1,6}-5_{2,3}$ (22GHz) and SiO J=1-0, 2-1, 3-2 maser lines (43, 86, 129GHz) toward five post-AGB (candidate) stars, using the 21-m single-dish telescopes of the Korean VLBI Network. Depending on the target objects, 7 - 11 epochs of data were obtained. We detected both $H_2O$ and SiO maser lines from four sources: OH16.1-0.3, OH38.10-0.13, OH65.5+1.3, and IRAS 19312+1950. We could not detect $H_2O$ maser emission toward OH13.1+5.1 between the late OH/IR and post-AGB stage. The detected $H_2O$ masers show typical double-peaked line profiles. The SiO masers from four sources, except IRAS 19312+1950, show the peaks around the stellar velocity as a single peak, whereas the SiO masers from IRAS 19312+1950 occur above the red peak of the $H_2O$ maser. We analyzed the properties of detected maser lines, and investigated their evolutionary state through comparison with the full widths at zero power. The distribution of observed target sources was also investigated in the IRAS two-color diagram in relation with the evolutionary stage of post-AGB stars. From our analyses, the evolutionary sequence of observed sources is suggested as OH65.5+1.3${\rightarrow}$OH13.1+5.1${\rightarrow}$OH16.1-0.3${\rightarrow}$OH38.10-0.13, except for IRAS 19312+1950. In addition, OH13.1+5.1 from which the $H_2O$ maser has not been detected is suggested to be on the gateway toward the post-AGB stage. With respect to the enigmatic object, IRAS 19312+1950, we could not clearly figure out its nature. To properly explain the unusual phenomena of SiO and $H_2O$ masers, it is essential to establish the relative locations and spatial distributions of two masers using VLBI technique. We also include the $1.2-160{\mu}m$ spectral energy distribution using photometric data from the following surveys: 2MASS, WISE, MSX, IRAS, and AKARI (IRC and FIS). In addition, from the IRAS LRS spectra, we found that the depth of silicate absorption features shows significant variations depending on the evolutionary sequence, associated with the termination of AGB phase mass-loss.

• Journal of the Korean Chemical Society
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• v.45 no.6
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• pp.570-576
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• 2001

The europium doped yttrium oxybromide phosphors were synthesized by solid-state reaction method. The YOBr: $Eu^{3+}$ phosphor showed a strong and narrow red emission band at 621 nm and maximum emission intensity obtained when 0.05 mol Eu ions were doped. The red emission of $Eu^{3+}$ originated from $^5D_0$ ${\rightarrow}$ $^7F_2$electric dipole transition. In order to investigate on photoluminescence behavior, several experimental skills and numerical fittings are conducted to the YOBr: $Eu^{3+}$ phosphor. The emission spectrum was measured in the UV range and then decay curve of $^5D_0$ ${\rightarrow}$ $^7F_j$transitions was examined. The energy interaction type of YOBr: $Eu^{3+}$ phosphor was dipole-dipole interaction. In addition to the calculating by critical concentration, the critical distance ($R_0$) was calculated by decay curve fitting parameter from Inokuti-Hirayamas equation, and spectral overlap method. The critical distance was 17.03, 10.51 and 7.18$\AA$ for those methods, respectively. As considering systematic error of measurements, these values are within the same order, so that the above fitting methods are plausible and recommendable.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.4
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• pp.372-382
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• 2006

Most of the conventional breakwaters impermeable breakwaters which block seawater exchange between the outside and inside of the harbors. The blocking of seawater exchange may cause pollution of water in harbors. To solve the water pollution problem, various kinds of seawater exchange breakwaters have been proposed. Their types can be classified into the current type which uses tidal current, and the overtopping type which uses the wave energy. The overtopping type breakwaters require a discharge coefficient to calculate the rate of overtopping into the harbor. The present study is to compute the rate of overtopping with introduction of a correct discharge coefficient and to evaluate the effect of the overtopping type breakwater on the water qualify inside a harbor. The rate of overtopping was computed by using Forchheimer formula with time dependent mild-slope equation for various wave conditions. The formula has been generally used to calculate the overflow discharge in steady state river flows. The discharge coefficient, which is the key parameter of the calculation, was determined by a series of hydraulic model tests. The present scheme was applied to the seawater exchange section of the western breakwater of Jeju New Harbor's and the efficiency of that section was examined. The calculated results showed that the rate of overtopping into the harbor reached about $27.5m^3/s$ in the wave condition (wave height 3.7 m, wave period 8.5s, and wave direction NNW).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.12
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• pp.1129-1135
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• 2013

In this, three types of natural gas were employed to investigate the effect of low-calorific natural gas on the performance of and emissions from a heavy-duty CNG engine. The performance and emission characteristics were analyzed by conducting a full-load test, WHSC mode test, and WHTC mode test. The results showed that the torque of low-calorific natural gas with $9,800kcal/Nm^3$ of higher heating value decreased by 4.4 compared to that of the current natural gas with $10,400kcal/Nm^3$ of heating value. With low-calorific fuels, CO, $CO_2$, and $NO_x$ emissions decreased. However, THC emissions increased. According to the WHSC and WHTC mode test results, the thermal efficiency increased and the emission characteristics showed a similar trend to the full-load test results. Low-calorific natural gases cause a decrease in torque at full-load operation conditions and an increase in hydrocarbon emissions.

• Reproductive and Developmental Biology
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• v.38 no.4
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• pp.171-177
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• 2014

L-Carnitine is an antioxidant for the transport of fatty acids in mitochondria and breakdown of lipids for metabolic energy. Some studies have suggested that carnitine improves sperm motility in mammals. The objective of this study was to investigate the effect of L-carnitine on the characteristics in fresh semen of miniature pigs. The collected fresh semen was stored in modena B medium with L-carnitine (0, 1.0, 2.0, and 4.0 mg/ml) for 10 days at $18^{\circ}C$. The semen quality of viability, acrosome reaction and mitochondria integrity was analyzed on 0, 3, 7, and 10 day of semen storage. The percentages of live and dying sperm were not different among treatment groups with different concentrations of L-carnitine during the storage period. In acrosome reaction analysis, when the sperm stored for 7 day, the percentages of live sperm with acrosome reaction were significantly (p<0.05) lower in 1 ($9.0{\pm}0.9%$), 2 ($7.6{\pm}0.2%$) or 4 mg/ml ($7.9{\pm}0.8%$) L-carnitine-treated groups than the control group (0 mg/ml L-carnitine) ($11.12{\pm}0.2%$). However, there were no difference in percentages of live sperm with acrosome reaction for 3 and 10 days of storage with each concentrations of L-carnitine. When sperm was stored for 3 and 10 days, the percentages of live sperm with mitochondria integrity were significantly higher in 2 mg/ml of L-carnitine-treated group than control group (p<0.05). In conclusion, the L-carnitine has a positive effect on acrosome reaction and mitochondria integrity in liquid state of fresh semen in miniature pigs.

• Journal of Physiology & Pathology in Korean Medicine
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• v.19 no.1
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• pp.29-37
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• 2005

According to Confucianism, the world before Confucius focused on respecting the heaven which meant that everything could be done by the heaven. After the period of Confucianism, Joo-Ja asserted that everything could be done by nature. During the Chosun Dynasty, philosophers such as Seo Kyung-duck, Lee Hwang, and Lee Yi talked about four characters and seven passions of human being. They started to focus more on the inside of human nature. During the later period of the Chosun Dynasty, a philosopher by the name of Dongmugong Lee Jema analyzed that one's nature and feelings can change his or her external matter and the function of internal organs by purity or impurity of one's mind. Based on these analysis, Dongmugong discovered 'sasangin' which puts more emphasis on one's state of mind compared to the outside the world. Also, Dongmugong tried to figure out the connections between Confucianism and medical science. If you use change fire and stone theory which is difference between hado and nock-seo to expain four seven theory one's mind could be define as four natural characters and seven feelings. From four seven theory four is ying and seven is yang. This is the method of cure and understand the structure of human body. And also, four natural characters and seven feelings can be divided into heaven and earth. You can see Four natural characters is far more similar to heaven and seven feelings are similar to earth. According to four-seven theory hado is permanent and you can find out 'sasangin' is permanent also. Since seven feelings are influenced by sam-jae, you can analogize there are 21 different types in 'sasangin'. An underlying principle should there be 28 different types of sasangin instead of 21 different types of sasangin but one quater of sasangin is hidden according to samhyuniljang theory. All creations in the world are organized by unification of the great absolute and symmetry distinction of yingyang. With these facts identity of the heaven, earth and man which is named samjae generates symbols of independent sasang. And also, sasang generates relations between five element, six energy and the six family relation. From six family relation comes seven feelings of man which creates a category of the eight trigrams for divination and unification of nine palace. All these process are united.

• Tunnel and Underground Space
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• v.26 no.2
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• pp.59-67
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• 2016

In this paper, we perform a numerical analysis to evaluate the potential of fault reactivation during gas production from hydrate bearing sediments and the moment magnitude of induced seismicity. For the numerical analysis, sequential coupling of TOUGH+Hydrate and FLAC3D was used and the change in effective stress and consequent geomechanical deformation including fault reactivation was simulated by assuming that Mohr-Coulomb shear resistance criterion is valid. From the test production simulation of 30 days, we showed that pore pressure reduction as well as effective stress change hardly induces the fault reactivation in the vicinity of a production well. We also investigated the influence of stress state conditions to a fault reactivation, and showed that normal fault stress regime, where vertical stress is relatively greater than horizontal, may have the largest potential for the reactivation. We tested one simulation that earthquake can be induced during gas production and calculated the moment magnitude of the seismicity. Our calculation presented that all the magnitudes from the calculation were negative values, which indicates that induced earthquakes can be grouped into micro-seismic and as small as hardly perceived by human beings. However, it should be noted that the current simulation was carried out using the highly simplified geometric model and assumptions such that the further simulations for a scheduled test production and commercial scale production considering complex geometric conditions may produce different results.

• Korean Journal of Remote Sensing
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• v.33 no.5_1
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• pp.507-519
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• 2017

The applications of NDVI (Normalized Difference Vegetation Index) as a vegetation index has been widely used to understand vegetation biomass and physiological activities. However, NDVI is not suitable way for monitoring vegetation stress because it is less sensitive to change in physiological state than biomass. PRI (Photochemical Reflectance Index) is well developed to present physiological activities of vegetation, particularly high-light-stress condition, and it has been adopted in several satellites to be launched in the future. Thus, the understanding of PRI performance and the development of analysis method will be necessary. This study aims to interpret the characteristics of light-stress-sensitive PRI in shadow areas and to evaluate the PRI calculated by other wavelengths (i.e., 488.9 nm, 553.6 nm, 646.9 nm, and 668.4 nm) instead of 570 nm that used in original PRI. Using airborne-based hyperspectral image, we found that PRI values were increased in shadow detection due to the reduction of high light induced physiological stress. However, the qualities of both PRI and NDVI data were dramatically decreased when the shadow index (SI) exceeded the threshold (SI<25). In addition, the PRI calculated using by 553.6 nm had best correlation with original PRI. This relationship was improved by multiple regression analysis including reflectances of RED and NIR. These results will be helpful to the understanding of physiological meaning on the application of PRI.