• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.51-56
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• 2011

A test range for a 75tf class gas generator cycle liquid propellant rocket engine is defined. The engine system test range is defined by the performance variation during flight, the dispersion after engine calibration, and additional margin. The component development test range includes the operation range corresponding to the engine system test range and the component performance margin.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.51.2-51.2
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• 2020

Luminous blue variables (LBVs) are massive evolved stars that show unpredictable photometric and spectral variation. It is generally assumed that they undergo one or more of large eruptions. We have obtained high dispersion NIR spectra of several LBVs with Immersion GRating INfrared Spectrometer (IGRINS). One notable feature in their IGRINS spectra is the existence of broad lines (~ a few hundred km/s) with unusual boxy profile. They are fluorescent lines of Fe II by Lyman α photons in the stellar wind. However, modeling of these lines with radiative transfer code CMFGEN predicts much weaker line strength. We propose that incorporating broadening of Lyman α line by scattering processes in dense wind can enhance the Fe II fluorescent lines. We further discuss how these Fe II fluorescent lines can be used to characterize massive LBV wind.

• Journal of the Korean GEO-environmental Society
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• v.2 no.3
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• pp.5-15
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• 2001

The purpose of this study is to find sedimentation patterns variation before and after the Saemangeum reclamation. Water circulations before and after the Saemangeum reclamation are calculated diagnostically and prognostically from the water temperature, salinity data, wind data and tidal residual current. Three dimensional movements of injected particles due to currents, turbulence and sinking velocity are tracked by the Euler-lagrange method. The dispersion range of soil grain for one and three day after releasing in the Geum river indicates that the soil grain was sedimented coastal area of Janghang and outer harbor of Kunsan. The soil grain moves a quite distance from the release point when size of soil grain is a small. These results indicate that size of soil grain and residual current is greatly influenced on the dispersion range of soil grain.

• Journal of Korean Society of Transportation
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• v.26 no.1
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• pp.191-201
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• 2008

It has been employed TRANSYT-7F and NETSIM to evaluate the validity and effectiveness of improvement on TSM(Transportation Systems Management). But T7F is hard to describe platoon compression and dispersion in actually, and NETSIM takes a long time for network coding, calibration and have difficulty in setting up saturation flow. While Shockwave Model have advantage which can describe platoon compression and dispersion in actually and shorten hours, convenience of application. But Shockwave Model apply unrealistic traffic flow relation ship(U-K curve) and simplify platoon because of difficulty in calculating shockwave's position and cross. For solving limitation of existing shockwave models, It develop new model with 2-regime linear model, New platoon model, Extended shockwave, etc. For verifying the validity of the proposed model, it was compared with delay of T7F and NETSIM by offset variation. In conclusion, it is thought that proposed model have outstanding performance to simulate traffic phenomenon.

• Composites Research
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• v.18 no.1
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• pp.38-44
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• 2005

In this paper, the group velocity dispersion curves of the $S_o$ symmetric mode in unidirectional CFRP plate was calculated as varying the propagating direction. The group velocity curve was obtained with the group velocities of the $S_o$ symmetric mode corresponding to 0.2 MHz-mm under the first cut-off frequency in the dispersion curves, and corrected by introducing the slowness curve. The velocities of the $S_o$ symmetric mode in the unidirectional CFRP plate were measured as varying the propagating direction and compared with the col?rotted group velocity curve. The measured velocities were good agreement with the corrected group velocity curve except near the fiber direction which was called the cusp region. It implies that the direction of the group velocities incline toward the fiber direction of the unidirectional CFRP plates when the propagation direction is not accorded with the principal axis. It is supposed that this phenomenon rerults from the preferential propagating the energy toward the direction with the faster propagation velocity.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.1
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• pp.49-52
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• 2008

To study the optical transmittance through nickel thin films with various thicknesses. Methods: We measured the optical transmittance through thin nickel film with various thicknesses. Results: The thickness dependence of the optical transmittance through nickel thin films deposited by thermal evaporation had been investigated. The optical transmittance rapidly decreased with the Ni film thickness less than 70 nm while it slightly decreased with the thickness more than 70 nm. In the experiment of optical dispersion, most of the light transmitted in the incidence direction. The result of experiment showed that optical dispersion was negligibly. Conclusions: Optical transmittance exponentially decreased as nickel thin film thickness increased.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.12
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• pp.98-106
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• 2013

The duty-cycle synchronization among mobile sensor nodes with energy-harvesting is very important. The nodes should keep their duty-cycle same to others as much as possible because they have to cooperate each other and to consume energy efficiently. The distribution of node position in network affects not only node connectivity but also the active time of synchronized nodes, and it relates to network life-time finally. In this paper, we introduce a network topology change algorithm (TCA) for energy-harvesting mobile sensor networks based on self-synchronized duty-cycling. The algorithm tries to change a network topology into a balanced topology where the mobile sensor nodes are unified according to the density of the number of nodes. For TCA, both fluid flow algorithm and flock dispersion algorithm are proposed and they are evaluated through the simulation in agent based modeling language. TCA is applied to the energy-harvesting mobile sensor networks to improve the synchronization of duty-cycle and to reduce the variation of energy consumption among nodes.

• Economic and Environmental Geology
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• v.27 no.4
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• pp.387-396
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• 1994

Mineralogical and geochemical studies on gold-bearing quartz veins and wallrock from the Mugeug mine were carried out in order to investigate the variation of mineralogical composition and the geochemical behavior of elements with distance from the gold-bearing quartz veins. Gold-bearing quartz veins occur in early Cretaceous medium- to coarse-grained biotite granite. The unaltered wallrock is composed mainly of quartz, plagioclase, orthoclase, microcline, biotite and hornblende with accessory minerals of sphene and apatite. Mineralogical changes in altered wallrock around the gold-bearing quartz veins were observed as follows; 1) biotite and hornblende altered into chlorite, and next to sericite, 2) plagioclase, orthoclase and microcline altered into sericite, and 3) calcite and quartz introduced into wallrock. Contents of $K_2O$, Rb, Cs, Au, As and Sb in altered wallrock increase, whereas those of $Na_2O$, CaO, Ba, and Sr decrease with proximity to the gold-bearing quartz veins. The loss on ignition also increases with the increase of alteration mineral. The width of primary dispersion increases in order $Au=SiO_2<As=Cs=Rb<K_2O=Sb$ and $MnO<Na_2O=CaO=Ba<Sr$. The sericitization index, $K_2O/(K_2O+Na_2O)$, is an important indicator to interpret the degree of alteration at the Mugeug mine, which is more than 0.8 in strongly and moderately altered granite, 0.5~0.8 in wea altered granite, and less than 0.5 in unaltered granite. Alteration indices for major and trace elements, and the ratio of Rb/Sr are also useful to discriminate alteration zones.

• Polymer(Korea)
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• v.32 no.1
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• pp.1-6
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• 2008

The adhesion behaviors and processability of NBR as a sealing material were investigated. In order to find the optimum formulation, the adhesive properties and processability were observed as the change of the contents of acrylonitrile (ACN) in NBR. Effects of Mooney viscosity, filler, plasticizer and crosslinking agent on the adhesion behaviors were also studied. The contents of ACN in NBR have great effects on adhesion behaviors and processability in NBR sealing. To know the optimum condition of roll mixing, degree of dispersion was investigated. It was confirmed that degree of dispersion was influenced by various factors such as mixing order, time, and temperature. The crosslinking system was studied as the observation of sulfur system, peroxide system, crosslinking density, and structure. From the variation of the dry condition and hexamine contents, the relation between adhesive and NBR was studied. These results show the adhesion properties and processability are dependent on the contents of ACN and crosslinking system.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.933-936
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• 2008

An engineered cementitious composite (Engineered Cementitious Composite) had been developed in previous study. Theoretical prediction of the tensile stress-strain relation of ECC is important in providing the material constitutive relation necessary for designing structural members. But, few studies have been reported with regard to predicting the tensile stress-strain relation of ECC. Prediction of the tensile stress-strain relation of ECC accounting for actual bridging curve, such as fiber dispersion is needed. The present study extends the work as developed by Kanda et al., by modeling the bridging curve, accounting for fiber dispersion, the degree of matrix spalling, and fiber rupture to predict the tensile stress-strain relation of ECC. The role of material variation in the bridging curve, such as number of effective fiber actually involved in the bridging capacity and how it affects the multiple cracking process is discussed. The approach for formulating the tensile stress-strain relation is discussed next, where the procedure for obtaining the necessary parameters, such as the crack spacing, is presented. Finally, the predicted stress-strain relation will be validated with experimental tests results.