• Aerospace Engineering and Technology
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• v.10 no.1
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• pp.45-53
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• 2011

This paper is technical review about Direct Sequence Spread Spectrum(DSSS) to apply in launch vehicle system. First, we introduce communication protocol(carrier frequency, code length, process gain, data rate, chip rate etc) about several application system using DSSS. And then, we survey and summarize the effect of doppler shift to the DSSS. The doppler shift is important error factor for PN code tracking in the fast moving system like launch vehicle. So, spread spectrum code acquisition technique for a direct sequence system in the presence of doppler effect must be investigated.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.181-181
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• 2010

현대 반도체 금속배선 연구에서는 기존에 쓰이던 Al (Aluminium) 금속배선 대신에 Cu (Copper) 금속배선 연구가 진행되고 있다. Cu는 Al 보다 비저항이 낮고, 녹는점도 Al보다 높다는 장점이 있지만 저온에서 기판인 Si (Silicon) 과 반응하고 접착력이 우수하지 못 하다는 단점이 있다. 이런 문제를 해결하기 위하여 확산방지막을 기판과 금속배선 사이에 삽입하는 방법이 제시 되었다. 확산방지막으로는 기존에 쓰이던 Ti (Titanium) 계열의 확산방지막과 W (Tungsten) 계열의 확산방지막이 있다. 이번 연구에서는 W 계열의 확산방지막에 불순물 C (Carbon) 과 N (Nitrogen) 을 첨가한 W-C-N 확산방지막 시편을 제조하였고, N2의 비율을 변화시키며 $600^{\circ}C$, $800^{\circ}C$열처리를 하였다. 본 실험의 결과로, 확산방지막의 $N_2$ 농도가 0, 0.5, 2 sccm으로 증가할수록 고온에서도 Elastic modulus 와 Hardness 값이 시편의 여러 영역에서 비교적 안정적으로 유지된다는 결과를 얻었다. 이 결과로부터 W-C-N 박막의 질소 농도에 따라 고온에서도 비교적 안정적으로 유지된다는 결과를 얻었다. 본 연구에서 시편은 RF magnetron sputtering 방법으로 제작하였고 Elastic modulus와 Hardness의 측정은 Hysitron사의 Triboindenter를 이용하였다. Indenting에 사용된 압입팁은 Berkovich tip을 사용하였다.

• Journal of the Korean Chemical Society
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• v.38 no.6
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• pp.427-434
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• 1994

The retention behaviors of poly(ethylene-co-vinyl acetate)s have been studied by thermal field-flow fractionation(ThFFF) with respect to effective separation and characterization of thermal diffusion coefficients($D_{\tau}$) as one of the physicochemical properties of polymers. The eight copolymers are different in vinyl acetate composition ranging from 25% to 70% and in molecular weight ranging from 110,000 to 285,000. The carrier solvents are THF, toluene and chlorobenzene which have different viscosities and thermal conductivities. It is shown that the retention of a copolymer is dependent on the type of the carrier, the molecular weight and chemical composition of the copolymer. The results show that the retention of a copolymer increases when either vinyl acetate composition or the molecular weight increase. $D_{\tau}$ values measured by experiments vary from 1.36∼5.97 $\cm^2/(s.K)$ depending on the copolymer composition and the type of the carrier solvent. These values increase $(r^2{\geq}0.928)$ with increase of weight % of vinyl acetate. THF is found to be the proper carrier solvent for separation of copolymers employed in this study due to the fact that a $D_{\tau}$ value greatly changes with variation of copolymer composition. From the above results, ThFFF can be used for separation of copolymers with similar molecular sizes but different compositions.

• Journal of Korea Water Resources Association
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• v.39 no.5 s.166
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• pp.395-403
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• 2006

This study suggests the use of a simple method, called the unit concentration response function(UCRF) for predicting travel time and dispersion of pollutants with the minimum information of study area instead of numerical models which are widely used In the Previous studies. However, the numerical models require time-consuming, tedious effort, and many data sets. So we derive the UCRF using some components such as travel time, peak concentration, and passage time of pollutant etc. We use the regression equation for the estimations of components which were developed from the investigations of many river basins in USA. This study used the regression equaiton for the UCRF to the accident of Dichloromethane leak into the Nakdong River occurred on June 30, 1994 and applied the UCRF for the predictions of travel time and dispersion. The predictions were compared with the results by QUAL2E model. The results by the regression equaiton and QUAL2E model had a good agreement between observed and simulated concentrations. Therefore, the regression equation for the UCRF which can simply estimate travel time and concentration of pollutants showed its applicability for the ungaged basin.

• Korean journal of applied entomology
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• v.59 no.4
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• pp.383-391
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• 2020

The vertical distribution and dispersion of the two-spotted spider mite, Tetranychus urticae and its predator, Phytoseiulus persimilis, were investigated within and between green pepper plants. We also tested the effect of an artificial bridge with threads on dispersal of P. persimilis between the plants. The extent of spread of T. urticae depended on its infested density and location. When 10 adults of T. urticae were inoculated on upper leaf, they stayed on the upper leaf until 5 days after inoculation. However, when 100 adults were inoculated on an upper leaf, they dispersed to the lower leaf within a day. In condition that 10 adults of T. urticae were inoculated on the lower leaf, they started to move toward upward within a day. In the absence of T. urticae, P. persimilis tended to move to the leaves where T. urticae was present when both T. urticae and P. persimilis were inoculated together within a plant. An artificial bridge with threads between two plants was helpful to disperse P. persimilis to neighboring plants. Therefore, it would be expected that the dispersal of P. persimilis can be promoted by supplying the artificial bridges among plants and by narrowing the distances between plants.

• Proceedings of the KGS Conference
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• 2004.05a
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• pp.90-90
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• 2004

한인 13가구가 최초로 러시아로 이주한 1863년 이후 그 수는 기하급수적으로 증가하였다. 초기에는 국경지대를 중심으로 한인촌을 형성하였으나 점차 연해주는 물론 동시베리아 지역으로까지 확산되었다. 블라디보스토크에서도 도시의 건설 및 성장과 함께 한인 집단 거주지가 형성되었고, 두 차례 에 걸친 강제 이주와 한 번의 자발적 이주로 위치가 이동하였다. (중략)

• Journal of the Korean Society of Radiology
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• v.2 no.2
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• pp.31-38
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• 2008

Line scan diffusion weighted imaging (LSDI) pulse sequence for 0.32 T magnetic resonance imaging (MRI) system was developed. In the LSDI pulse sequence, the imaging volume is formed by the intersection of the two perpendicular planes selected by the two slice-selective $\pi$/2-pulse and $\pi$-pulse and two diffusion sensitizing gradients placed on the both side of the refocusing $\pi$-pulse and the standard frequency encoding readout was followed. Since the maximum gradient amplitude for the MR system was 15 mT/m the maximum b value was $301.50s/mm^2$. Using the developed LSDI pulse sequence, the diffusion weighted images for the aqueous NaCl solution phantom and triacylglycerol solution phantom calculated from the line scan diffusion weighted images gives the same results within the standard error range (mean diffusivities = $963.90{\pm}79.83({\times}10^{-6}mm^2/s)$ at 0.32 T, $956.77{\pm}4.12({\times}10^{-6}mm^2/s)$ at 1.5 T) and the LSDI images were insensitive to the magnetic susceptibility difference and chemical shift.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.9 no.1
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• pp.33-40
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• 2011

In the compacted bentonite containing $Ag_2O$, the transport of iodide ion was investigated by Through-diffusion method. It is confirmed that Iodide ion is transported by diffusion process in the compacted bentonite containing $Ag_2O$ as well as in the compacted bentonite without $Ag_2O$. However, the lag-time of iodide ion in the compacted bentonite containing $Ag_2O$ is larger than that in the compacted bentonite without $Ag_2O$. The increase of the lag-time was observed in pure iodide ion solution and also in 0.1M NaCl-iodide ion solution. The apparent diffusion coefficient of iodide ion in the compacted bentonite containing $Ag_2O$ has lower value than that in the compacted bentonite without $Ag_2O$. The effect of $Ag_2O$ on the effective diffusion coefficient was not clearly investigated in the compacted bentonite containing $Ag_2O$ while the values of effective diffusion coefficient of iodide ion in the compacted bentonite without $Ag_2O$ obtained in this study were similar to those in the compacted bentonite reported in the literature.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.10 no.4
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• pp.165-173
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• 1998

Analytical solutions to predict the movement rate of submerged mound are derived using the convection coefficient and the joint distribution function of wave heights and periods. Assuming that the sediment is moved onshore due to the velocity asymmetry of Stokes' second order nonlinear wave theory, the micro-scale bedload transport equation is applied to the sediment conservation. The nonlinear convection-diffusion equation can then be obtained which governs the migration of submerged mound. The movement rate decreases exponentially with increasing the water depth, but the movement rate tends to increase as the spectral width parameter, $ u$ increases. In comparison of the analytical solution with the measured data, it is found that the analytical solution overestimates the movement rate. However, the agreement between the analytical solution and the measured data is encouraging since this over-estimation may be due to the inaccuracy of input data and the limitation of sediment transport model. In particular, the movement rates with respect to the water depth predicted by the analytical solution are in very good agreement with the estimated result using the discritization technique with the hindcast wave data.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1990.06a
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• pp.53-56
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• 1990