• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.835-841
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• 2013

Modern solid-state gyroscopes (HRG) with hemispherical resonators from high-purity quartz glass and special surface superfinishing and ultrathin gold coating become the best instruments for precise-grade inertial reference units (IRU) targeting long-term space missions. Designing of these sensors could be a notable contribution into development of Korea as a space nation. In participial, 40mm diameter thin-shell resonator from high-purity fused quartz, fabricated as a single-piece with its supporting stem has been designed, machined, etched, tuned, tested, and delivered by STM Co. (ATS of Ukraine) several years ago; an extremely-high Q-factor (upto 10~20 millions) has been shown. Understanding of the best way how to match such a unique sensor with inner glass assembly of the gyro means how to use the high potential in a maximal extent; and this has become the urgent task. Inner quartz glass assembly has a very thin indium (In) layer soldered the resonator and its silica base (case), but effects of internal resonances between operational modal pair of the shell-cup and its side (parasitic) modes can notable degrade the potential of the sensor as a whole, instead of so low level of resonator's intrinsic losses. Unfortunately, there are special combinations of dimensions of the parts (so-called, "resonant sizes"), when intensive losses of energy occurs. The authors proposed to use the length of stem's fixture as an additional design parameter to avoid such cases. So-called, a cyclic scheme of finite element method (FEM) and ANSYS software were employed to estimate different combinations of gyro assembly parameters. This variant has no mismatches of numerical origin due to FEM's discrete mesh. The optimum length and dangerous "resonant lengths" have been found. The special attention has been paid to analyses of 3D effects in a cup-stem transient zone, including determination of a difference between the positions of geometrical Pole of the resonant hemisphere and of its "dynamical Pole", i.e., its real zone of oscillation node. Boundary effects between the shell (cup) and 3D short "beams" (inner and outer stems) have been ranged. The results of the numerical experiments have been compared with the classic model of a quasi-hemispherical shell band with inextensional midsurface, and the solution using Rayleigh's functions of the $1^{st}$ and $2^{nd}$ kinds. To guarantee the truth of the recommended sizes to a designer of the real device, the analytical and FEM results have been compared with experimental data for a party of real resonators. The consistency of the results obtained by different means has been shown with errors less than 5%. The results notably differ from the data published earlier by different researchers.

• Macromolecular Research
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• v.10 no.3
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• pp.158-167
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• 2002

In order to endow with new bioactive functionality from small intestine submucosa (SIS) powder as natural source to poly (L-lactide) (PLA) and poly (lactide-co-glycolide) (PLGA) synthetic biodegradable polymer, porous SIS/PLA and SIS/PLGA as natural/synthetic composite scaffolds were prepared by means of the solvent casting/salt leaching methods for the possibility of the application of tissue engineered bone and cartilage. A uniform distribution of good interconnected pores from the surface to core region was observed the pore size of 40~500 ${\mu}{\textrm}{m}$ independent with SIS amount using the solvent casting/salt leaching method. Porosities, specific pore areas as well as pore size distribution also were almost same. After the fabrication of SIS/PLA hybrid scaffolds, the wetting properties was greatly enhanced resulting in more uniform cell seeding and distribution. Five groups as PGA non-woven mesh without glutaraldehyde (GA) treatment, PLA scaffold without or with GA treatment, and SIS/PLA (Code No.3 ; 1 : 12 of salt content, (0.4 : 1 of SIS content, and 144 ${\mu}{\textrm}{m}$ of median pore size) without or with GA treatment were implanted into the back of nude mouse to observe the effect of SIS on the induction of cells proliferation by hematoxylin and eosin, and von Kossa staining for 8 weeks. It was observed that the effect of SIS/PLA scaffolds with GA treatment on bone induction are stronger than PLA scaffolds, that is to say, in the order of PLA/SIS scaffolds with GA treatment > PLA/SIS scaffolds without GA treatment > PGA nonwoven > PLA scaffolds only with GA treatment = PLA scaffolds only without GA treatment for the osteoinduction activity. The possible explanations are (1) many kinds of secreted, circulating, and extracellular matrix-bound growth factors from SIS to significantly affect critical processes of tissue development and differentiation, (2) the exposure of SIS to GA resulted in significantly calcification, and (3) peri-implant fibrosis due to covalent bonding between collagen molecule by crosslinking reaction. In conclusion, it seems that SIS plays an important role for bone induction in SIS/PLA scaffolds for the application of tissue engineering area.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.7
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• pp.441-448
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• 2016

The thrust force created by a propeller depends on the incoming flow velocity and the rotational velocity of the propeller. The performance of the propeller can be described by dimensionless variables, advanced ratio, thrust coefficient, and power coefficient. This study included the application of the immersed boundary lattice Boltzmann method (IBLBM) with the stereo lithography (STL) file of the rotating object for performance analysis. The immersed boundary method included the addition of the external force term to the LB equation defined by the velocity difference between the lattice points of the propeller and the grid points in the domain. The flow by rotating a 4-blade propeller was simulated with various Reynolds numbers (Re) (including 100, 500 and 1000), with advanced ratios in the range of 0.2~1.4 to verify the suggested method. The typical tendency of the thrust efficiency of the propeller was obtained from the simulation results of different advanced ratios. It was also necessary to keep the maximum mesh size ratio of the propeller surface to a grid size below 3. Additionally, a sufficient length of the downstream region in the domain was maintained to ensure the numerical stability of the higher Re and advanced ratio flow.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.6
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• pp.95-101
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• 2002

There are many effective parameters to high concentration ozone generation. These parameters became very important elements should be considered before designing ozone generator. After designing, there are many peripheral parameters to greatly affect to high concentration ozone generation also. In this study, of many effective peripheral parameters on high concentration ozone generation, the effects of flow rate of inlet oxygen gas and some kinds of additional gases on ozone concentration were investigated As a result, when inlet oxygen gas was introduced at the range of 0.75［LPM］～2.00［LPM］ the highest ozone concentration of 71145［ppm］ was obtained at 1.25［LPM］. When the additional nitrogen gas was mixed to oxygen gas at the range of 0.0［vol%]～6.4［vol%］ the highest ozone concentration of 73135［ppm］ was obtained at 0.8［vol%］ of nitrogen gas. This showed 3［%］ increasing compared to the case of pure oxygen gas inlet. When the additional argon gas was mixed to oxygen gas at the range of 0.0［vol%］～6.4［vol%］ the highest concentration of 67288［ppm］was obtained at 0.8［vol%］of argon gas. This is decreased value compared to that of introducing the pure oxygen.

• Proceedings of the Mineralogical Society of Korea Conference
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• 2003.05a
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• pp.66-66
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• 2003

King George island, Antarctica, is mostly covered by ice sheet and glaciers, but the land area is focally exposed for several thousand years after deglaciation. For a mineralogical study of chemical weathering in the polar environment, glacial debris was sampled at the well-developed patterned ground which was formed by long periglaclal process. As fresh equivalents, recently exposed tills were sampled at the base of ice cliff of outlet glaciers and at the melting margin of ice cap together with fresh bedrock samples. Fresh tills are mostly composed of quartz, plagioclase, chlorite, and illite, but those derived from hydrothermal alteration zone contain smectite and illite-smectite. In bedrocks, chlorite was the major clay minerals in most samples with minor illite near hydrothermal alteration zone and interstratified chlorite-smectite in some samples. Smectite closely associated with eolian volcanic glass was assigned to alteration in their source region. Blocks with rough surface due to chemical disintegration showed weathering rinds of several millimeter thick. Comparision between inner fresh and outer altered zones did not show notable change in clay mineralogy except dissolution of calcite and some plagioclase. Most significant weathering was observed in the biotite flakes, eolian volcanic glass, sulfides, and carbonates in the debris. Biotite flakes derived from granodiorite were altered to hydrobiotite and vermiculite of yellow brown color. Minor epitactic kaolinite and gibbsite were formed in the cleaved flakes of weathered biotite. Pyrite was replaced by iron oxides. Calcite was congruently dissolved. Volcanic glass of basaltic andesite composition showed alteration rim of several micrometer thick or completely dissolved leaving mesh of plagioclase laths. In the alteration rim, Si, Na, Mg, and Ca were depleted, whereas Al, Ti, and Fe were relatively enriched. Mineralization of lichen and moss debris is of much interest. They are rich of A3 and Si roughly in the ratio of 2:1 to 3:1 typical of allophane. In some case, Fe and Ti are enriched in addition to Al and Si. Transmission electron microscopy of the samples rich of volcanic glass showed abundant amorphous aluminosilicates, which are interpreted as allophane. Chemical weathering in the King George Island is dominated by the leaching of primary phyllosilicates, carbonates, eolian volcanic glass, and minor sulfides. Authigenesls of clay minerals is less active. Absence of a positive evidence of significant authigenic smectite formation suggests that its contribution to the clay mineralogy of marine sediments are doubtful even near the maritime Antarctica undergoing a more rapid and intenser chemical weathering under more humid and milder climate.

• Journal of Korea Water Resources Association
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• v.52 no.10
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• pp.697-706
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• 2019

A multiphase flow modeling approach equipped with a hybrid turbulence modeling method is applied to compute the gravity currents in a rectangular channel. The present multiphase solver considers the dense fluid, the less-dense ambient fluid and the air above free surface as three phases with separate flow equations for each phase. The turbulent effect is simulated by the IDDES (improved delayed detach eddy simulation), a hybrid RANS/LES, approach which resolves the turbulent flow away from the wall in the LES mode and models the near wall flow in RANS mode on moderately fine computational meshes. The numerical results show that the present model can successfully reproduce the gravity currents in terms of the propagation speed of the current heads and the emergence of large-scale Kelvin-Helmholtz type interfacial billows and their three dimensional break down into smaller turbulent structures, even on the relatively coarse mesh for wall-modeled RANS computation with low-Reynolds number turbulence model. The present solutions reveal that the modeling approach can capture the large-scale three dimensional behaviors of gravity current head accompanied by the lobe-and-cleft instability at affordable computational resources, which is comparable to the LES results obtained on much fine meshes. It demonstrates that the multiphase modeling method using the hybrid turbulence model can be a promising engineering solver for predicting the physical behaviors of gravity currents in natural environmental configurations.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.323-328
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• 2019

In order to construct 3D geospatial information about the terrain, current measurement using a total station, remote sensing, GNSS(Global Navigation Satellite System) have been used. However, ground survey and GNSS survey have time and economic disadvantages because they have to be surveyed directly in the field. In case of using aerial photographs and satellite images, these methods have the disadvantage that it is difficult to obtain the three-dimensional shape of the terrain. The terrestrial LiDAR can acquire 3D information of X, Y, Z coordinate and shape obtained by scanning innumerable laser pulses at densely spaced intervals on the surface of the object to be observed at high density, and the processing can also be automated. In this study, terrestrial LiDAR was used to analyze slope displacement. Study area slopes were selected and data were acquired using LiDAR in 2016 and 2017. Data processing has been used to generate slope cross section and slope data, and the overlay analysis of the generated data identifies slope displacements within 0.1 m and suggests the possibility of using slope LiDAR on land to manage slopes. If periodic data acquisition and analysis is performed in the future, the method using the terrestrial lidar will contribute to effective risk slope management.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.2
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• pp.138-144
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• 2023

In this study, the effect of electrochemical treatment in mitigating alkali leaching into an aquatic environment was investigated. To modify the surface of cement paste, 1000 mA/m² of the direct current was passed through anodic graphite to the external mesh for 4 weeks. Then, the cement paste specimen was exposed to still water in air-tight condition to prevent natural healing of alkali leaching in the water. For 100 days of monitoring in water, the pH value was marginally increased at the electrochemical treatment, while control specimen ranked to the even higher pH accounting for 13.2 in the pH. Moreover, after the pH monitoring, the pH profile for the paste specimen indicated that the electrochemical treatment was effective in securing the higher alkalinity of cement matrix. The water obtained from alkali leaching process, was used to ecological test for Daphnia magna. It was evident that the electrochemical treatment had minimal adverse effect on ecological impact, while control specimen mostly immobilized the standard Daphnia magna.

• Fisheries and Aquatic Sciences
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• v.27 no.4
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• pp.240-255
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• 2024

Widas Reservoir is situated in an area of 570 ha in the Pajaran Village, Madiun Regency, East Java Province, Indonesia, playing an essential role in fisheries, with the average fish catch per year of about 283 tons/year. This study explores the standing stock, growth parameters, mortality, and exploitation rates of several dominant fishes in Widas Reservoir. This study was carried out from February to November 2019. Fish stocks were estimated using acoustic tools, fish catch records, and sizes collected by local enumerators. Fish length frequency sampling was conducted on several dominant fish species, such as Oreochromis niloticus, Barbonymus gonionotus, and Osteochilus vittatus. Based on the length-frequency data, estimating fish population dynamics, the fish population dynamics (infinitive length (L_∞) and growth coefficient (K)) estimation was run in a time series using the Fish Sock Analysis Tool, II (FISAT II) program package. Moreover, the estimation of natural mortality parameters, the fishing mortality parameter, and the exploitation rate was also performed. The approximated overall fish stock in the Widas Reservoir was about 79,848 kg, which lowered with the increase in water depth. Of particular concern, in the surface layer at a depth between 1-5 m, the fish stock reached 58,813 kg, while in the deeper zone (> 15 m), the value significantly lowered by about 98%, reaching 1,219 kg. These results indicate an overfishing in the Widas Reservoir. The value of the exploitation rate (E) of B. gonionotus was 0.748, O. niloticus 0.8, and O. vittatus 0.7, respectively, proving the overfishing states occurred in the study area. Therefore, regulations governing the number of catches and the use of fishing gear are crucial in Widas Reservoir, particularly the use of lift and gill nets with a mesh size of less than 2 cm.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.5 no.3
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• pp.245-254
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• 2000

This study was conducted to investigate the community structure and distributional pattern of meiobenthos in the deep sea bottoms of northeastern Pacific during July 1998. The faunal samples were collected using the multiple corer at ten stations; eight stations along the transects from 5$^{\circ}$N to 12$^{\circ}$N, and two stations in the Preservation Zone and Impact Zone of the KODOS (Korea Deep Ocean Study) area. The organic carbon content in sediments ranged from 0.79 to 1.76 mg cm$^{-3}$, and higher concentration appeared at stations in lower latitudes than 8$^{\circ}$N. The most abundant meiobenthos was nematodes and followed by foraminiferans; these two taxa comprised more than 70% of the total abundance at all stations. The most abundant meiobenthos occurred with mesh size of 0.063 nm. The maximum density of meiobenthos was 442 ind./10 cm$^2$ at station N5, and the density gradually decreased toward station N8 where the minimum density of 92 md./10 cm$^2$ was found. More than 60% of meiobenthos were distributed at surface sediment layer within 1.0 cm, and the peak abundance was found at 0-0.25 cm layer. The latitudinal distribution pattern of meiobenthos in the study area seemed to be related with the primary productivity of the surface water that is also connected to the water circulation pattern of the Pacific Ocean near the Equator, diverging at latitude of 8$^{\circ}$N and conversing at 5$^{\circ}$N.