• 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 .

• Korean Journal of Food Science and Technology
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• v.26 no.2
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• pp.110-116
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• 1994

In order to study the effects of enzyme modification on the physico-chemical and functional properties of myofibrillar protein prepared from the frozen sardine, Sardinops melanostica, the protein was hydrolyzed with pepsin under the enzyme-substrate ratio 1:100 at $37^{\circ}C$ and pH 1.65 for 1, 4, 8, 12, and 24 hr, respectively. The properties of pepsin-modified sardine myofibriliar protein were determined. The extents of proteolysis with pepsin as a fuction of time was showed a typical enzyme hydorlysis curve with an initial region of 4 hour period followed by plateau region. The SDS-acrylamide slab gel electrophoresis patterns of pepsin-modified proteins showed mainly disappearances of minor protein bands, but no changes of main protein bands. The gel filtration patterns through Sephadex G-75 of sardine myofibrillar protein showed two big peaks and three small peaks. All the small peaks were disappearanced by proteolysis with pepsin in one hour. and during the period of proteolysis the fast big peak became gradually smaller and the late big peak eluted more slowly. By proteolysis, the emulsifying activity and emulsifying capacity of sardine myofibrillar protein were all decreased. The effects of pepsin-modification on emulsifying capacity were greater than those on emulsifying activity of protein. The aeration capacity of the protein was increased about 1.9 folds and the foam stability decreased to 0.6 folds of control by pepsin-modification. The pepsin-modified sardine myofibrillar proteins showed about 0.6 folds of heat coagulation and 1.4 folds of viscosity of control. The pH dependence of solubilities of sardine myofibrillar protein showed two isoelectric areas of pH 5 and 9. The pepsin-modified protein showed more clear pH dependences at the early stage but not at the late stage of proteolysis.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.4
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• pp.634-643
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• 2005

The aim of this study is to evaluate the effects of blue light emitting diode (LED) Light Curing Units (FreeLight 2, L.E.Demetron I, Ultra-Lume 5) on the microhardness of three resin composites (Z250, Point 4, Dyract AP) and to determine their optimal curing time. Samples were made using acrylic molds $(2.0mm{\times}3mm)$ of each composite. All samples were prepared over a Mylar strip placed on a flat glass surface. After composite placement on the molds, the top surface was covered with another Mylar strip and a glass slab was gently pressed over it. The times of irradiation were as follows: Elipar TriLight, 40 s; Elipar FreeLight 2. L.E.Demetron I, and Ultra-Lume 5, 10s, 20s, 40s, respectively. Mean hardness values were calculated at the top and bottom for each group. ANOVA and Sheffe's test were used to evaluate the statistical significance of the results. Results showed that FreeLight 2, Ultra-Lume 5, and L.E.Demetron I were able to polymerize point 4 in 20 seconds to a degree equal to that of the halogen control at 40 seconds. FreeLight 2 and L.E.Demetron I were able to polymerize Z250 in 10 seconds to a degree equal to that of the halogen control at 20 seconds. FreeLight 2 and L.E.Demetron I were able to polymerize Dyract AP in 10 seconds to a degree equal to that of the halogen control at 40 seconds. The commercially available LED curing lights used in this study showed an adequate microhardness with less than half of the exposure time of a halogen curing unit.

• The Journal of the Petrological Society of Korea
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• v.20 no.2
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• pp.77-98
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• 2011

The igneous complex consisting of mangerite and gabbro in the Odaesan area, the eastem part of the Gyeonggi Massif, South Korea, intruded early Paleo-proterozoic migmatitic gneiss. The mangerite is composed of orthopyroxene, clinopyroxene, amphibole, biotite, plagioclase, pethitic K-feldspar, quartz. The gabbro has similar mineral assemblage but gabbro has minor amounts of amphibole and no perthitic K-feldspar. The gabbro occurs as enclave and irregular shaped body within the mangerite, and the boundary between the mangerite and gabbro is irregular. Leucocratic lenses with perthitic K-feldspar are included in the gabbro enclaves. These textures represent mixing of two different magmas in liquid state. SHRIMP U-Pb zircon age dating gave $234{\pm}1.2$ Ma and $231{\pm}1.3$ Ma for mangerite and gabbro, respectively. These ages are similar with the intrusion ages of post collision granitoids in the Hongseong (226~233 Ma) and Yangpyeong (227~231 Ma) areas in the Gyeonggi Massif. The mangerite and gabbro are high Ba-Sr granites, shoshonitic and formed in post collision tectonic setting. These rocks also show the characters of subduction-related igneous rock such as enrichment in LREE, LILE and negative Nb-Ta-P-Ti anomalies. These data represent that the mangerite and gabbro formed in the post collision tectonic setting by the partial melting of an enriched lithospheric mantle during subduction which occurred before collision. The heat for the partial melting was supplied by asthenospheric upwelling through the gab between continental and oceanic slabs formed by slab break-off after continental collision. The distribution of post-collisional igneous rocks (ca. 230 Ma) in the Gyeonggi Massif including Odaesan mangerite and gabbro strongly suggests that the tectonic boundary between the North and South China blocks in Korean peninsula passes the Hongseong area and futher exteneds into the area between the Yangpyeong-Odaesan line and Ogcheon metamorphic belt.

• Progress in Medical Physics
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• v.13 no.3
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• pp.149-155
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• 2002

Recent advances in radiation transport algorithms, computer hardware performance, and parallel computing make the clinical use of Monte Carlo based dose calculations possible. To compare the speed and accuracies of dose calculations between different developed codes, a benchmark tests were proposed at the XIIth ICCR (International Conference on the use of Computers in Radiation Therapy, Heidelberg, Germany 2000). A Monte Carlo treatment planning comprised of 28 various Intel Pentium CPUs was implemented for routine clinical use. The purpose of this study was to evaluate the performance of our system using the above benchmark tests. The benchmark procedures are comprised of three parts. a) speed of photon beams dose calculation inside a given phantom of 30.5 cm$\times$39.5 cm $\times$ 30 cm deep and filled with 5 ㎣ voxels within 2% statistical uncertainty. b) speed of electron beams dose calculation inside the same phantom as that of the photon beams. c) accuracy of photon and electron beam calculation inside heterogeneous slab phantom compared with the reference results of EGS4/PRESTA calculation. As results of the speed benchmark tests, it took 5.5 minutes to achieve less than 2% statistical uncertainty for 18 MV photon beams. Though the net calculation for electron beams was an order of faster than the photon beam, the overall calculation time was similar to that of photon beam case due to the overhead time to maintain parallel processing. Since our Monte Carlo code is EGSnrc, which is an improved version of EGS4, the accuracy tests of our system showed, as expected, very good agreement with the reference data. In conclusion, our Monte Carlo treatment planning system shows clinically meaningful results. Though other more efficient codes are developed such like MCDOSE and VMC＋＋, BEAMnrc based on EGSnrc code system may be used for routine clinical Monte Carlo treatment planning in conjunction with clustering technique.

• Investigative Magnetic Resonance Imaging
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• v.2 no.1
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• pp.96-103
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• 1998

Purpose : To assess the clinical utility of turbo contrast-enhanced magnetic resonance angiography(CE MRA) in the evaluation of the aortic arch and its major branches and to compare the image quality of CE MRA among different coils used. Materials and Methods : Turbo three-phase dynamic CE MRA encompassing aortic arch and its major branches was prospectively performed after manual bolus IV injection of contrast material in 29 patients with suspected cerebrovascular diseases at 1.0T MR unit. the raw data were obtained with 3-D FISH sequence (TR 5.4ms, TE 2.3ms, flip angle 30, slab thickness 80nm, effective slice thickness 4.0mm, matrix size $100{\times}256$, FOV 280mm). Total data acquisition time was 4. to 60 seconds. We subjectively evaluated the imge quality with three-rating scheme : "good" for unequivocal normal finding, "fair" for relatively satisfactory quality to diagnose 'normal' despite intravascular low signal, and "poor" for equivocal diagnosis or non-visualization of the origin or segment of the vessels due to low signal or artifacts which needs catheter angiography. At the level of the carotid bifurcation, it was compared with conventional 2D-TOF MRA image. Overall image quality was also compared visually and quantitatively by measuring signal-to-noise ratios (SNRs) of the ascending aorta, the innominate artery and both common carotid arteries among the three different coils used(CP body array(n=12), CP neck array(n=9), and head-and-neck(n=8). Results : Demonstration of the aortic arch and its major branches was rated as "good" in 55% (16/29) and "fair" in 34%(10/29). At the level of the carotid bifurcation, image quality of turbo CE MRA was same as or better than conventional 2D-TOF MRA in 65% (17/26). Overall image quality and SNR were significantlygreater with CP body array coil than with CP neck array or head-and-neck coil. Conclusions : Turbo CE MRA can be used as a screening exam in the evaluation of the major branches of the aortic arch from their origin to the skull base. Overall imagequality appears to be better with CP body array coil than with CP neck array coil or head-and-neck coil.

• Journal of the Korean Society for Railway
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• v.20 no.5
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• pp.668-682
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• 2017

Alignments of railways recently constructed in Korea have been straightened due to the advent of high-speed rail, which means increasing the numbers of tunnels and bridges. Overbreak during tunnel construction may be unavoidable, and is very influential on overall stability. Over-excavation in tunneling is also one of the most important factors in construction costs. Overbreak problems around crown areas have decreased with improvements of excavation methods, but overbreak problems around bottom areas have not decreased because those areas are not very influential on tunnel stability compared with crown areas. The filling costs of 10 cm thickness of overbreak at the bottom of a tunnel are covered under construction costs by Korea Railway Authority regulations, but filling costs for more than the covered thickness are considered losses of construction cost. The filling material for overbreak bottoms of tunnels should be concrete, but concrete and mixed granular materials with fractured rock are also used for some sites. Tunnels in which granular materials with fractured rock are used may have a discontinuous section under the concrete slab track. The discontinuous section influences the propagation of waves generated from train operation. When the bottom of a tunnel is filled with only concrete material, the bottom of the tunnel can be considered as a continuous section, in which the waves generated from a train may propagate without reflection waves. However, a discontinuous section filled with mixed granular materials may reflect waves, which can cause resonance of vibration. The filled materials and vibration propagation characteristics are studied in this research. Tunnel bottom filling materials that have ratios of granular material to concrete of 5.0 %, 11.5 %, and 18.0 % are investigated. Samples were made and tested to determine their material properties. Static numerical analyses were performed using the FEM program under train operation load; test results were found to satisfy the stability requirements. However, dynamic analysis results show that some mixed ratios may generate resonance vibration from train operation at certain speeds.

• The Journal of the Petrological Society of Korea
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• v.16 no.2 s.48
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• pp.82-99
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• 2007

The Paleogene dikes intruding into the late Cretaceous granodiorite are pervasively observed in the Irun-myeon, eastern Geoje Island. They are classified into three groups: NW-trending acidic dike swarm and WNW- (A-Group) and $NS{\sim}NNE-trending$ (B-Group) basic dike swarms. Based on their cross-cutting relationships, the earliest is the acidic dike group and fellowed by A- and B-Groups in succession. The acidic dikes seem to have intruded into tension gashes induced by the sinistral strike-slip faulting of the Yangsan fault system during the late $Cretaceous{\sim}early$ Paleogene. In terms of rock-type, orientation, age, and geochemistry, A-Group and B-Group are intimately correlated with the intermediate and basic dike swarms in the Gyeongju-Gampo area, respectively. These results significantly suggest that the corresponding dike swarms are genetically related. Based on the K-Ar and Ar-Ar age data, A- and B- Groups were intruded during $64{\sim}52\;Ma$ and $51{\sim}44\;Ma$, respectively. The result means that the direction of tensional stress in and around the SE Korean peninsula was changed abruptly from NNE-SSW to $EW{\sim}WNW-ESE$ at about 51 Ma. Considering the tectonic environments during the Paleogene, it is interpreted that A-Group was injected along the WNW-trending tensional fractures developed under an regional sinistral simple shear regime which was caused by the north-northwestward oblique subduction of the Pacific plate beneath the Eurasian plate. Meanwhile, the regional stress caused by the collision of India and Eurasia continents at about 55 Ma was likely propagated to the East Asia at about 51 Ma, and then the East Asia including the Korean peninsula was extruded eastwards as a trench-rollback and the dip of downgoing slab of the Pacific plate was abruptly steepened. As a result, the strong suction-force along the plate boundary produced a tensional stress field trending EW or WNW-ESE in and around the Korean peninsula, which resultantly induced B-Group to intrude passively into the study area.

• Economic and Environmental Geology
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• v.42 no.5
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• pp.403-412
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• 2009

The objective of this study is to investigate the geochemical change of feldspar minerals by supercritical $CO_2$, which exists at $CO_2$ sequestration sites. High pressurized cell system (100 bar and $50^{\circ}C$) was designed to create supercritical $CO_2$ in the cell and the surface change and the dissolution of plagioclase and orthoclase were observed when the mineral surface reacted with supercritical $CO_2$ and water (or without water) for 30 days. The polished slab surface of feldspar was contacted with supercritical $CO_2$ and an artificial brine water (pH 8) in the experiments. The experiments for the reaction of feldspar with only supercritical $CO_2$ (without brine water) were also conducted. Results from the first experiment showed that the average roughness value of the plagioclase surface was 0.118 nm before the reaction, but it considerably increased to 2.493 nm after 30 days. For the orthoclase, the average roughness increased from 0.246 nm to 1.916 nm, suggesting that the dissolution of feldspar occurs in active when the feldspars contact with supercritical $CO_2$ and brine water at $CO_2$ sequestration site. The dissolution of $Ca^{2+}$ and $Na^+$ from the plagioclase occurred and a certain part of them precipitated inside of the high pressurized cell as the form of amorphous silicate mineral. For the orthoclase, $Al^{3+}$, $K^+$, and $Si^{+4}$ were dissolved in order and the kaolinite was precipitated. In the experiments without water, the change of the average roughness value and the dissolution of feldspar scarcely occurred, suggesting that the geochemical reaction of feldspars contacted with supercritical $CO_2$ at the environment without the brine water is not active.

• Journal of Korean Society of Steel Construction
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• v.23 no.4
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• pp.503-514
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• 2011

In this research, the seismic connection details for two concrete-filled U-shape steel beam-to-H columns were proposed and cyclically tested under a full-scale cruciform configuration. The key connecting components included the U-shape steel section (450 and 550 mm deep for specimens A and B, respectively), a concrete floor slab with a ribbed deck (165 mm deep for both specimens), welded couplers and rebars for negative moment transfer, and shear studs for full composite action and strengthening plates. Considering the unique constructional nature of the proposed connection, the critical limit states, such as the weld fracture, anchorage failure of the welded coupler, local buckling, concrete crushing, and rebar buckling, were carefully addressed in the specimen design. The test results showed that the connection details and design methods proposed in this study can well control the critical limit states mentioned above. Especially, the proposed connection according to the strengthening strategy successfully pushed the plastic hinge to the tip of the strengthened zone, as intended in the design, and was very effective in protecting the more vulnerable beam-to-column welded joint. The maximum story drift capacities of 6.0 and 6.8% radians were achieved in specimens A and B, respectively, thus far exceeding the minimumlimit of 4% radians required of special moment frames. Low-cycle fatigue fracture across the beam bottom flange at a 6% drift level was the final failure mode of specimen A. Specimen B failed through the fracture of the top splice plate of the bolted splice at a very high drift ratio of 8.0% radian.