• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.5
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• pp.175-181
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• 2005

Ingots of rutile single crystals were grown by the skull melting method, and their characteristics were compared in terms of melt-dwelling time for each melt. The method is based on direct inductive heating of an electrically conducted melt by an alternating RF field, and the heating is performed by absorption of RF energy. $TiO_2$ is an insulator at room temperature but its electric conductivity increases elevated temperature. Therefore, titanium metal ring(outside diameter : 6cm, inside diameter : 4cm, thickness 0.2cm) was embedded into $TiO_2$, powder (anatase phase, CERAC, 3N) for initial RF induction heating. Important factors of the skull melting method are electric resistivity of materials at their melting point, working frequency of RF generator and cold crucible size. In this study, electric resitivity of $TiO_2$, $(10^{-2}\~10^{-1}\;{\Omega}{\cdot}m)$ at its melting point was estimated by compairing the electric resitivities of alumina and zirconia. Inner diameter and height of the cold crucible was 11 and 14cm, respectively, which were determined by considering of the Penetration depth $(0.36\~1.13cm)$ and the frequency of RF generator.

• Journal of Adhesion and Interface
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• v.19 no.3
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• pp.106-112
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• 2018

Recently, the hyperthermia treatment of malignant tissues has gained great attention as a biocompatible and benign method that facilitates successful cancer therapy compared to radiation and chemotherapy. In this study, superparamagnetic ($Fe_3O_4$) iron oxide nanoparticles (IONP) coated with biocompatible polymer (IONP@P(MPC/FOM)) for the purpose of hyperthermia treatment were prepared and related characterization were performed. IONPs with having 15 nm diameter were first prepared by coprecipitation and followed by surface modification with 4-cyanopentanoic acid dithiobenzoate (CTP) for reversible addition-fragmentation chain transfer (RAFT) copolymerization by using 2-methacryloyloxyethyl phosphorylcholine (MPC) and fluorescein O-methacrylate (FOM) to form corona layer of P(MPC/FOM) on the surface of the IONP. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) confirmed the morphology and hydrodynamic size of the IONP@P(MPC/FOM) and thermogravimetric analysis (TGA) confirmed the formation of P(MPC/FOM) corona layer, respectively. Exposing IONP dispersion to alternating magnetic field suggests that the IONP@P(MPC/FOM) aqueous dispersion with 0.2 wt.% can be used for hyperthermia treatment.

• Korean Journal of Weed Science
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• v.7 no.1
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• pp.19-28
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• 1987

These experiments were conducted to recognize the germination change in relation to storage period, using 25 kinds of field-collected weed seeds stored under the dry and low temperature ($4{\pm}1^{\circ}C$), and to establish a simple germination induction methods in some kinds of them. No or weak dormancy was observed in Lepidium virginicum, Rumex japonicus, Cirsium japonicum var. ussuriense, Aeschnomene indica and Ludwigia prostrate. The germination of Digltaria sanguinalis, Portulaca oleracea, Amaranthus spp., Echinochloa crux-galli, Polygonum persicaria, Cyperus iria, and Aeschynnmene indica was enhanced by $H_2SO_4$ treatment for 20, 2, 2, 50, 40, 3 or 5 minutes, respectively. Favorable germination in Polygonum persicaria and Echinochloa crus-galli was obtained by soaking in water for 25 days and 50 days, respectively. Moisture treatment for 21 days and 14 days caused the enhancement of germination in Cyperus difformis and Aneilema keisak, respectively. Combination of various treatments in Cyperus iria was most effective when the seeds treated with $H_2SO_4$ for 3 minutes incubated in alternating temp. after soaking in 0.2% $KNO_3$, but their effect on Digitaria sanguinnlis was little.

• KSBB Journal
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• v.22 no.6
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• pp.409-413
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• 2007

Polydiacetylene(PDA)-based sensors possess a number of properties that can be successfully applied for label-free detection system. PDA is one of the most attractive color-generating materials, with growing applications as sensors. Here we introduce various PDA-based devices, used as biosensor, chemosensor, thermosensor, and optoelectronics sensor. In general, PDA liposomes and films are closely packed and properly designed for polymerization via 1,4-addition reaction to form an ene-yne alternating polymer chain. PDA-based two/three dimensional structures have been used for colorimetric or fluorescent devices, sensing biological as well as chemical components. This color-generating material also present a very high charge carrier mobility, allowing its application as field-effect transistor (FET). The immobilized PDA structures or films have distinct advantages for the detection of low concentration target molecules over the aqueous solution-based detection systems. In the present review, reported detection methods by using various PDA structures are summarized with updated references.

• Korean Journal of Agricultural and Forest Meteorology
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• v.2 no.4
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• pp.204-208
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• 2000

Little information is available for the temporal variation in air temperature profile within rice canopies under development, while much works have been done for a fully developed canopy. Fine wire thermocouples of 0.003 mm diameter (chromel-constantan) were installed at 10 vertical heights by a 10 cm step in a paddy rice field to monitor the air temperatures over and within the developing rice canopy from one month after transplanting (June 29) to just before heading (August 24). According to a preliminary analysis of the data, we found neither the daytime temperature maximum nor the night time minimum at the active radiation surface (the canopy height with maximum leafages) during this period, which is a typical profile of a fully developed canopy. Air temperature within the canopy never exceeded that above the canopy at 1.5 m height during the daytime. Temporal march of the within-canopy profile seemed to be controlled mainly by the ambient temperature above the canopy and the water temperature beneath the canopy, and to some extent by the solar altitude, resulting in alternating isothermal and inversion structures.

• Economic and Environmental Geology
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• v.19 no.1
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• pp.67-83
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• 1986

Oriented hand samples were collected from Gobangsan Formation and Nogam Formation in the north of Danyang and south of Yeongchun, from Bansong Group in and around Danyang, from Nampo Group in Chungnam Coalfield, from Gyeongsang Supergroup distributed from Waegwan through Daegu to Gyeongsan and from Daegu to Goryong, and from volcanic flows in Jeongog area and Jeju Island to study the paleomagnetism of southern Korea since Permian. Stepwise alternating field and thermal demagnetization experiments were carried out to determine optimum fields and temperatures. Observed mean paleomagnetic directions are as follows: $D=331.5^{\circ}$, $I=25.1^{\circ}$, $a95=12.8^{\circ}$ for Permian, $D=325.6^{\circ}$, $I=46.1^{\circ}$, $a95=11.8^{\circ}$ for Triassic, $D=313.4^{\circ}$, $I=43.1^{\circ}$, $a95=16.0^{\circ}$ for early Jurassic, $D=41.3^{\circ}$, $I=64.6^{\circ}$, $a95=4.5^{\circ}$ for early Cretaceous, $D=28.3^{\circ}$, $I=58.1^{\circ}$, $a95=2.3^{\circ}$ for late Cretaceous, $D=2.0^{\circ}$, $I=55.8^{\circ}$, $a95=6.6^{\circ}$for Quaternary. To describe the tectonic translocation of southern Korean block, northern Eurasian continental block was used as a reference frame. For each age since Permian the expected northern Eurasian field directions in terms of paleolatitude and declination were calculated. The paleolatitudes of Permian ($13.2^{\circ}N$) and early Jurassic ($25.1^{\circ}N$) obtained from the study area are quite different from those of Permian ($66.0^{\circ}N$) and early Jurassic ($68.1^{\circ}N$) which are expected for northern Eurasia. The declinations of Permian ($331.5^{\circ}$) and early Jurassic ($313.4^{\circ}$) are also quite different from those of the Permian ($56.6^{\circ}$) and the early Jurassic ($47.5^{\circ}$) expected for northern Eurasia. The Cretaceous paleolatitude is similar to the expected within error limit, but the declination for the same period is significantly different from that of the expected for the northern Eurasia. From the above evidences it is suggested that the south Korean land mass had moved from low latitude in Permian to north and sutured to northern continental block since early Jurassic. The relative rotations of early Cretaceous($27.4^{\circ}$) and late Cretaceous($10.8^{\circ}$) to northern Eurasian continent reveal that the Korean land mass might be rotated clockwise in two different times, probably in late Early Cretaceous and in Tertiary.

• Journal of Biomedical Engineering Research
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• v.23 no.1
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• pp.49-60
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• 2002

Receive dynamic focusing with an array transducer can provide near optimum resolution only in the vicinity of transmit focal depth. A customary method to increase the depth of field is to combine several beams with different focal depths, with an accompanying decrease in the frame rate. In this Paper. we Present a simultaneous multiple transmit focusing method in which chirp signals focused at different depths are transmitted at the same time. These chirp signals are mutually orthogonal in a sense that the autocorrelation function of each signal has a narrow mainlobe width and low sidelobe levels. and the crossorelation function of any Pair of the signals has values smaller than the sidelobe levels of each autocorrelation function. This means that each chirp signal can be separated from the combined received signals and compressed into a short pulse. which is then individually focused on a separate receive beamformer. Next. the individually focused beams are combined to form a frame of image. Theoretically, any two chirp signals defined over two nonoverlapped frequency bands are mutually orthogonal In the present work. however, a tractional overlap of adjacent frequency bands is permitted to design more chirp signals within a given transducer bandwidth. The elevation of the rosscorrelation values due to the frequency overlap could be reduced by alternating the direction of frequency sweep of the adjacent chirp signals We also observe that the Proposed method provides better images when the low frequency chirp is focused at a near Point and the high frequency chirp at a far point along the depth. better lateral resolution is obtained at the far field with reasonable SNR due to the SNR gain in Pulse compression Imaging .

• Geophysics and Geophysical Exploration
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• v.24 no.4
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• pp.194-201
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• 2021

Induced polarization (IP) effect is known to be caused by electrochemical phenomena at interface between minerals and pore water. Spectral induced polarization (SIP) method is an electrical survey to localize subsurface IP anomalies while injecting alternating currents of multiple frequencies into the ground. This method was effectively applied to mineral exploration of various ore deposits. Titanomagnetite ores were being produced by a mining company located in Gonamsan area, Gwanin-myeon, Pocheon-si, Gyeonggi-do, South Korea. Because the ores contain more than 0.4 w% vanadium, the ore deposit is called as Gwanin vanadiferous titanomagnetite (VTM) deposit. The vanadium is the most important of materials in production of vanadium redox flow batteries, which can be appropriately used for large-scale energy storage system. Systematic mineral exploration was conducted to identify presence of hidden VTM orebodies and estimate their potential resources. In geophysical exploration, laboratory geophysical measurement of rock samples is helpful to generate reliable property models from field survey data. Therefore, we performed laboratory SIP data of the rocks from the Gwanin VTM deposit to understand SIP characteristics between ores and host rocks and then demonstrate the applicability of this method for the mineral exploration. Both phase and resistivity spectra of the ores sampled from underground outcrop and drilling cores were different of those of the host rocks consisting of monzodiorite and quartz monzodiorite. Because the phase and resistivity at frequencies below 100 Hz are mainly dependent on the SIP characteristics of the rocks, we calculated mean values of the ores and the host rocks. The average phase values at 0.1 Hz were ores: -369 mrad and host rocks: -39 mrad. The average resistivity values at 0.1 Hz were ores: 16 Ωm and host rocks: 2,623 Ωm. Because the SIP characteristics of the ores were different of those of the host rocks, we considered that the SIP survey is effective for the mineral exploration in vanadiferous titanomagnetite deposits and the SIP characteristics are useful for interpreting field survey data.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.6
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• pp.1230-1236
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• 2012

To verify that the electrokinetic remediation is effective for decreasing salinity of fields of the plastic-film house, field tests for physical property, chemical property, and crop productivity of soils have been conducted. The abridged result of those tests is as follows. In the EK treatment, the electrokinetic remediation has been treated at the constant voltage (about 0.8 V $cm^{-1}$) for fields of the farm household. At this time, an alternating current (AC) 220 V of the farm household was transformed a direct current. The HSCI (High Silicon Cast Iron) that the length of the stick for a cation is 20cm, and the Fe Plate for an anion have been spread out on the ground. As the PVC pipe that is 10 cm in diameter was laid in the bottom of soils, cations descend on the cathode were discharged together. For soil physical properties according to the EK treatment, the destruction effect of soil aggregate was large, and the infiltration rate of water was increased. However, variations of bulk density and porosity were not considerable. Meanwhile, in chemical properties of soils, principal ions of such as EC, $NO_3{^-}$-N, $K^+$, and $Na^+$ were better rapidly reduced in the EK treated control plot than in the untreated control plot. And properties such as pH, $P_2O_5$ and $Ca^{2+}$ had a small impact on the EK. For cropping season of crop cultivation according to the EK treatment, decreasing rates of chemical properties of soils were as follows; $NO_3{^-}$-N 78.3% > $K^+$ 72.3% > EC 71.6% $$\geq_-$$ $Na^+$ 71.5% > $Mg^{2+}$ 36.8%. As results of comparing the experimental plot that EK was treated before crop cultivation with it that EK was treated during crop cultivation, the decreasing effect of chemical properties was higher in the case that EK was treated during crop cultivation. After the EK treatment, treatment effects were distinct for $NO_3{^-}$-N and EC that a decrease of nutrients is clear. However, because the lasting effect of decreasing salinity were not distinct for the single EK treatment, fertilization for soil testing was desirable carrying on testing for chemical properties of soils after EK treatments more than two times. In the growth of cabbages according to the EK treatment, the rate of yield increase was 225.5% for the primary treatment, 181.0% for the secondary treatment, and 124.2% for third treatment compared with the untreated control plot. The yield was increased by a factor of 130.0% for the hot pepper at the primary treatment (Apr. 2011), 248.1% for the lettuce at the secondary treatment (Nov.2011), and 125.4% for the young radish at the third treatment (Jul. 2012). In conclusion, the effect of yield increase was accepted officially for all announced crops.

• Geophysics and Geophysical Exploration
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• v.10 no.1
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• pp.89-97
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• 2007

A three-dimensional (3D) magnetotelluric (MT) survey has been carried out to delineate subsurface structures and possible fractures, for development of low-temperature geothermal resources in Pohang, Korea. Quite good quality MT data could be obtained throughout the survey region by locating the remote reference in Kyushu, Japan, which is ${\sim}480\;km$ from the centre of the field site. 3D modelling and inversion are performed taking into account the sea effect in MT measurements near the seashore. The nearby sea in the Pohang area affects MT data at frequencies below $1\;Hz{\sim}0.2\;Hz$, depending on the distance from the seashore. The most severe sea effects were observed in the south-east parts of the survey area, closer to Youngil Bay. 3D inversion with and without the seawater constraint showed very similar results at shallow depths, roughly down to 2 km. At greater depths, however, a strong sea effect seems to form a fictitious conductive structure in ordinary 3D inversion, especially in the south-eastern part of the survey region. Comparison between drilling results and the resistivity profiles from inversions showed that five layered structures can be distinguished the subsurface beneath the target area. They are: (a) semi-consolidated mudstones with resistivity less than $10\;{\Omega}m$, which are ${\sim}300\;m$ thick in the northern part and ${\sim}600\;m$ thick in the southern part of the survey area; (b) occasional occurrence of trachybasalt and lapilli tuff within the mudstone layer has resistivity of a few tens of${\Omega}m$, (c) intrusive rhyolite ${\sim}400\;m$ thick has resistivity of several hundreds of ${\Omega}m$, (d) alternating sandstone and mudstone down to 1.5 km depth shows resistivity of ${\sim}100\;{\Omega}m$, (e) a conductive structure was found at a depth of ${\sim}3\;km$, but more geological and geophysical study should be carried out to identify this structure.