• Title/Summary/Keyword: 2-D DF

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Temperature Dependence of the Vibration-Vibration Energy Transfer for HF(v = n) + $H_2$(v = 0) and DF(v = n) + $D_2$(v = 0)

  • Lee, Chang-Soon;Kim, Yoo-Hang
    • Bulletin of the Korean Chemical Society
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    • v.13 no.1
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    • pp.11-17
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    • 1992
  • Vibration-to-vibration energy transfer probabilities for $HF(v=n)+H_2(v=0){\to}HF(v=n-1)+H_2(v=1)$ and $DF(v=n)+D_2(v=0){\to}DF(v=n-1)+D_2(v=1)$ including both the vibration-to-vibration and translation (V-V, T) and vibration-to-vibration and rotation (V-V, R) energy transfer paths have been calculated semiclassically using a simplified collision model and Morse-type intermolecular interaction potential. The calculated results are in reasonably good agreement with those obtained by experimental studies. They also show that the transition processes for $HF(v=1-3)+H_2(v=0){\to}HF(v=0-2)+H_2(v=1)$ and $DF(v=1,\;4)+D_2(v=0){\to}DF(v=0,\;3)+D_2(v=1)$ are strongly dependent on the V-V, T path at low temperature but occur predominantly via the V-V, R path with rising temperature. The vibration-to-vibration energy transfer for $HF(v=4)+H_2(v=0){\to}HF(v=3)+H_2(v=1)$ and $DF(v=2-3)+D_2(v=0){\to}DF(v=1-2)+D_2(v=1)$ occur predominantly via V-V, R path and V-V, T path through whole temperatures, respectively.

Effects of Pressure Ratio on Population Inversion in a DF Chemical Laser with Concurrent Lasing

  • Park, Jun-Sung;Baek, Seung-Wook
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.03a
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    • pp.287-293
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    • 2004
  • A numerical simulation is presented for investigating the effects of pressure ratio of $D_2$ injector to supersonic nozzle on the population inversion in the DF chemical laser cavity, while a lasing concurrently takes place. The laser beam is generated between the mirrors in the cavity and it is important to obtain stronger population inversion and more uniform distribution of the excited molecules in the laser cavity in order to produce high power laser beam with good quality. In this study, these phenomena are investigated by means of analyzing the distributions of the DF excited molecules and the F atom used as an oxidant, while simultaneously estimating the maximum small signal and saturated gains and power in the DF chemical laser cavity. For the numerical solution, an 11-species (including DF molecules in various excited states of energies), 32-step chemistry model is adopted for the chemical reaction of the DF chemical laser system. The results are discussed by comparison with two $D_2$injector pressure cases; 192 torr and 388.64 torr. Major results reveal that in the resonator, stronger population inversions occur in the all transitions except DF(1)-DF(0), when the $D_2$injection pressure is lower. But, the higher $D_2$injection pressure provides a favorable condition for DF(1)-DF(0) transition to generate the higher power laser beam. In other words, as the pressure of $D_2$injector increases, the maximum small signal gain in the $V_{1-0}$ transition, which is in charge of generating most of laser power, becomes higher. Therefore, the total laser beam power becomes higher.r.

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Numerical Analysis of Variations of Laser Parameters in DF Chemical Laser According to Pressure Ratio (불화중수소 화학레이저의 연료 및 산화제 분사 압력비에 따른 레이저 발진 성능 특성 변화에 관한 수치적 연구)

  • Park Jun Sung;Baek Seung Wook
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.10a
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    • pp.9-12
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    • 2004
  • A numerical simulation is presented for investigating the effects of pressure ratio of $D_2$ injector to supersonic nozzle on the Population inversion in the DF chemical laser cavity, while a latins concurrently takes place. In this study, these phenomena are investigated by means of analyzing the distributions of the DF excited molecules, while simultaneously estimating the maximum small signal gains and power in the DF chemical laser cavity. Major results reveal that the higher $D_2$ injection pressure provides a favorable condition for $DF^{(1)}$-$DF^{(0)}$ transition to generate the higher power laser beam.

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Output characteristics of a continuous wave deuterium fluoride chemical laser (연속발진 불화중수소 화학 레이저 출력특성)

  • 이정환;박병서;김재기
    • Korean Journal of Optics and Photonics
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    • v.13 no.1
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    • pp.65-69
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    • 2002
  • A continuous wave deuterium fluoride (DF) chemical laser was designed and manufactured, and we have achieved DF laser beam generation with the maximum output power of 101 W. The gain medium is vibration-rotationally excited DF molecules produced by F+D$_2$ cold reaction through supersonic diffusion mixing in an optical cavity. F atoms are produced in a combustor by F$_2$+ H$_2$ reaction and injected into the cavity through a supersonic nozzle. The optimal chemical efficiency was measured to be 5.12% and specific power to be 96.5 J/g.

Numerical Model Simulation of DF-CO$_2$ Transfer Chemical Laser

  • Kim, Sung-Ho;Cho, Ung-In
    • Bulletin of the Korean Chemical Society
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    • v.10 no.3
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    • pp.282-288
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    • 1989
  • Theoretical analysis of DF-$CO_2$ transfer chemical laser is performed through simple kinetic model consisting of 30 chemical reactions. In this model, we calculate the power theoretically by solving the rate equations, which are related to the $D_2\;+\;F_2$ chain reaction and the DF-$CO_2$ resonance energy transfer, combined with both the gain processes and the stimulated emission processes. The calculated powers are verified with previously reported results in good agreements. The output energy rises linearly with the increase in pressure, and the duration time of output pulse show the inverse dependence on pressure. Through the detailed calculation of temperature and concentrations of reactants as a function of time, it is found that the deactivation processes of DF(v) can be neglected in low pressure, but they have to be considered in high pressure. From the parametric study for the variation on [$D_2]/[F_2$] and [$CO_2]/[D_2\;+\;F_2$] at several constant total pressure, the optimum lasing conditions are found to be in a range of 1/3 to 1 and 2 to 4, respectively.

Low-Complexity Detection Techniques for Run-Length Limited Codes with d=2 (RLL(2,10) 변조 부호를 고려한 저복잡도 검출 기법)

  • 조한규;이보형;손희기;강창언;홍대식
    • Proceedings of the IEEK Conference
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    • 2000.11a
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    • pp.141-144
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    • 2000
  • PRML (partial response maximum-likelihood) 과 FDTS/DF (fixed-delay tree search with decision feedback)는 기록 저장 시스템에서 준최적의 성능을 보임이 잘 알려져 있다. 그러나, 위와 같은 정보열 검출 기법은 피할 수 없는 복잡도 문제를 가지고 있다. 본 논문은 최소 run 길이 제한조건 d=2를 가진 광기록 채널을 위한 다양한 저복잡도 검출 기법을 다룬다. 우선, 결정 궤환 기법을 이용한 이산 정합 여파기 (discrete matched filter with decision feedback:DMF/DF)가 기존의 PRML로부터 유도된다. 유도된 시스템은 PRML보다 결정 궤환에 의한 성능 이득을 갖는다. 또한, 메트릭 계산을 사용하지 않는 저복잡도 FDTS/DF가 유도된다. 모의실험 결과에 의하면, 유도된 저복잡도 검출 기법들은 기록 밀도 S>=5.5에서 P(D)=1+D+D/sup 2/+D/sup 3/의 target을 갖는 PRML보다 우수한 성능을 보인다.

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A NONEXISTENCE THEOREM FOR STABLE EXPONENTIALLY HARMONIC MAPS

  • Koh, Sung-Eun
    • Bulletin of the Korean Mathematical Society
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    • v.32 no.2
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    • pp.211-214
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    • 1995
  • Let M and N be compact Riemannian manifolds and $f : M \to N$ be a smooth map. Following J. Eells, f is exponentially harmonic if it represents a critical point of the exponential energy integral $$ E(f) = \int_{M} exp(\left\$\mid$ df \right\$\mid$^2) dM $$ where $(\left\ df $\mid$\right\$\mid$^2$ is the energy density defined as $\sum_{i=1}^{m} \left\$\mid$ df(e_i) \right\$\mid$^2$, m = dimM, for orthonormal frame $e_i$ of M. The Euler- Lagrange equation of the exponential energy functional E can be written $$ exp(\left\$\mid$ df \right\$\mid$^2)(\tau(f) + df(\nabla\left\$\mid$ df \right\$\mid$^2)) = 0 $$ where $\tau(f)$ is the tension field along f. Hence, if the energy density is constant, every harmonic map is exponentially harmonic and vice versa.

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Flow interference between two tripped cylinders

  • Alam, Md. Mahbub;Kim, Sangil;Maiti, Dilip Kumar
    • Wind and Structures
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    • v.23 no.2
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    • pp.109-125
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    • 2016
  • Flow interference is investigated between two tripped cylinders of identical diameter D at stagger angle ${\alpha}=0^{\circ}{\sim}180^{\circ}$ and gap spacing ratio $P^*$ (= P/D) = 0.1 ~ 5, where ${\alpha}$ is the angle between the freestream velocity and the line connecting the cylinder centers, and P is the gap width between the cylinders. Two tripwires, each of diameter 0.1D, were attached on each cylinder at azimuthal angle ${\beta}={\pm}30^{\circ}$, respectively. Time-mean drag coefficient ($C_D$) and fluctuating drag ($C_{Df}$) and lift ($C_{Lf}$) coefficients on the two tripped cylinders were measured and compared with those on plain cylinders. We also conducted surface pressure measurements to assimilate the fluid dynamics around the cylinders. $C_D$, $C_{Df}$ and $C_{Lf}$ all for the plain cylinders are strong function of ${\alpha}$ and $P^*$ due to strong mutual interference between the cylinders, connected to six interactions (Alam and Meyer 2011), namely boundary layer and cylinder, shear-layer/wake and cylinder, shear layer and shear layer, vortex and cylinder, vortex and shear layer, and vortex and vortex interactions. $C_D$, $C_{Df}$ and $C_{Lf}$ are very large for vortex and cylinder, vortex and shear layer, and vortex and vortex interactions, i.e., the interactions where vortex is involved. On the other hand, the interference as well as the strong interactions involving vortices is suppressed for the tripped cylinders, resulting in insignificant variations in $C_D$, $C_{Df}$ and $C_{Lf}$ with ${\alpha}$ and $P^*$. In most of the (${\alpha}$, $P^*$ ) region, the suppressions in $C_D$, $C_{Df}$ and $C_{Lf}$ are about 58%, 65% and 85%, respectively, with maximum suppressions 60%, 80% and 90%.

Soybean Growth and Yield as Affected by Spacing of Drainage Furrows in Paddy Field

  • Cho, Jin-Woong;Lee, Jung-June;Oh, Young-Jin;So, Jung-D.;Won, Jun-Yeon;Kim, Chang-Ho
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.51 no.1
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    • pp.26-31
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    • 2006
  • This study was conducted to determine the optimum number of inter-rows according to distance of drainage furrow (DF) for running-off excessive-water stress (EWS) in paddy field. The most soil water potential was shown in high ridge (distance of DF by 70 cm) cultivation and the soil water potential showed increasing tendency in over four inter-rows cultivation by DF. The growth of soybean reduced by extended inter-row and its reducing level was high, especially, over four inter-rows (DF distance by 2.8 m) because of EWS. The photosynthetic rate decreased in the more extensive field by distance of DF at V5 and R2 stages, especially, in over four interrows cultivation. Also, root activity decreased at wider DF. The yield was reduced with wider distance of DF more extensively, the highest yield of 270 g per $m^2$ at the every row, but yield showed decreasing tendency at over the $4^{th}$ row (2.8 m) cultivation. Soybean cultivation in paddy field could be founded with DF of every other or $4^{th}$ row.

Disfunctional Factors of R&D Information Retrieval Utilization: the Case of Environmental Science Database & Networks (환경.에너지 과학 R&D 정보 역기능 요인 분석: 디지털 네트워크 정보검색(NIR) 환경 적응사례)

  • 유사라
    • Journal of the Korean Society for information Management
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    • v.19 no.2
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    • pp.5-29
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    • 2002
  • This study explored the Dis-Functional(DF) factors associated with the information and utilization of the R&D outcomes which has been left behind in the environmental & energy science research field. Of the total of 225 sample surveyed, exactly 66.2% responded to the questions about DF factors. The major factors that have been experienced by the respondents included the followings : the shortage of manpower and budget, inadequate network utilities of resource sharing, unstable policies of digitalization of R&D databases and of presenting a specimen copy(not only report itself but also experimental data), deficient knowledge resource system for the specialized sub-research areas, absence of the process of TLO and commercialization of R&D results, and underestimation of the significance of quality control (evaluation) of academic and research information. Some recommendations for utilization of the R&D outcomes were suggested according to the DF factors investigated.