• Title/Summary/Keyword: Numerical Calculation

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The Resonance Frequency of Sound Channel in Shallow Water a Thermocline

  • Yan, Jin;Kim, Bong-Chae
    • The Journal of the Acoustical Society of Korea
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    • v.15 no.4E
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    • pp.65-71
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    • 1996
  • In shallow water with a thermocline, the characteristics of sound propagation strongly depend on the signal frequency. When only one of the source and the receiver is above the themocline, it is known that the intensity of the received signal changes largely and almost periodically as the signal frequency varies. This is the so-called channel resonance. By using the ray-mode approach, the formula relating the resonance frequency and the sound speed profile is obtained, and the resonance phenomenon is analyzed. Also this analysis is verified by numerical calculation.

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Limitation of a levitation system using a superconducting bulk (초전도 벌크를 이용한 자기부상 시스템의 한계)

  • 한승용;한송엽
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • 2001.02a
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    • pp.61-64
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    • 2001
  • Levitation force of a new magnetic levitation system using a super-conducting bulk magnet(SBM) and a permanent magnet(PM) was numerically calculated. The non-linear J-E relation of a SBM was modeled using a critical state model and iteration method, and demagnetization of a PM was considered using a demagnetization curve of a real PM. The maximum limitation of levitation force was found according to increasing the trapped field in a SBM. Finite element method was used for numerical calculation.

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A stability condition of minimal variance control with mismatch of time delay

  • Hashimoto, H.;Takenami, Y.;Akizuki, K.
    • 제어로봇시스템학회:학술대회논문집
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    • 1989.10a
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    • pp.918-923
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    • 1989
  • This paper presents a stability condition for Astrom's minimal variance control(MVC) with mismatch of time delay for a SISO ARMAX model containing time delay. The proof of the condition presented here is based on the characteristic equation in the feedback system and its magnitude. This condition, from easy numerical calculation, is able to find the stability of the feedback system without knowing the real time delay.

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Analysis of Propagation Properties in Junctions between Straight and Bent Waveguides Using Cylindrical Functions of Complex Order

  • Rashid, Mohd-Abdur;Masao Kodama
    • Proceedings of the IEEK Conference
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    • 2002.07b
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    • pp.711-714
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    • 2002
  • This paper presents a method to determine the propagation properties in the junctions between straight and bent waveguides using cylindrical functions of complex order. The proposed method was succeeded by developing the method of numerical calculation of cylindrical functions of complex order. As a result, we numerically calculate the reflection and transmission coefficients in the junctions in various situations, and we compare these results with the results by the perturbation method.

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development of kinematic analysis technique for pantograph structure design (판토그라프 구조설계를 위한 기구해석 기법 개발)

  • 박수홍;김휘준;정경렬;배정찬
    • Proceedings of the KSR Conference
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    • 1999.11a
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    • pp.107-114
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    • 1999
  • Pantograph, which collects current from cartenary system, is one of important parts of high-speed train. Kinematic analysis is basic component of pantograph design. But kinematic analysis is very complex and time-consuming. Therefore numerical calculation of pantograph kinematics is necessary. In this study, pantograph kinematic analysis software was developed and relationship between kinematic parameters and pantograph performance was investigated. The software and relationship between kinematic parameters and pantograph performance are helpful to pantograph designers

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Numerical Calculation of the Relaxation Spectrum from the Correlation Function$^\dag$

  • Lee, Hoo-Sung
    • Bulletin of the Korean Chemical Society
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    • v.8 no.5
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    • pp.406-408
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    • 1987
  • It has been shown that the distribution of relaxation times, H(ln $\tau$), in semi-logarithmic time scale can easily be calculated numerically from the derivative of the relaxation function in semilogarithmic scale. In that, ln$\tau$, the abscissa, is divided into N different segments of equal size, then H is considered to be a linear function of ln $\tau$within each segment. The technique has been applied to a Williams-Watts function as well as to the relaxation function obtained by photon correlation spectroscopy from atactic polystyrene glass. It has been demonstrated that the relaxation functions can be precisely reproduced from the calculated distribution functions.

A Study on the Ethanol Concentration by Osmotic Sink Reverse Osmosis Process (Osmotic Sink Reverse Osmosis Process를 이용한 에탄올의 농축특성에 관한 연구)

  • 이광현;민병렬
    • Membrane Journal
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    • v.2 no.1
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    • pp.33-48
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    • 1992
  • OSRO process was developed and it was confirmed more effective in ethanol concentrating process comparing to reverse osmosis process. It may be industrialized if more effective membrane for OSRO and reverse osmosis, which indicate the value greater than zero, it was shown that OSRO process was more effective than reverse osmosis for the ethanol concentration process. The decrease of feed concentration and flow rate and the increase of applied pressure made more effective operating conditions in OSRO process to concentrate ethanol. From the numerical esults for the multi-plates, theoretical DC values of reverse osmosis and OSRO process was increased as the umber of stages increased. DC values were increased with the increase of applied pressure in same number of stages. The theoretical values of DC by numerical calculation were corresponded to the experimental values within 15% tolerance. DC value was increased proportional to applied pressure and osmotic sink solution flow rate but it was decreased proportional to feed concentration and flow rate. The numerical calculation over the wide ranges inclading experimental condition was proposed in this study.

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Analysis of Creep Effective Stress in Austenitic Heat Resistant Steel (오스테나이트계 내열강의 크리프 유효응력 해석)

  • Nam, Ki-Woo;Park, In-Duck
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.7
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    • pp.1317-1323
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    • 2002
  • This paper describes the comparison of calculated effective stress with experimental one in austenitic heat resistant steels, STS310J1TB and STS310S with and without a small amount of Nb and N. Based on a solute atoms diffusion model, contribution from soluble nitrogen to the high-temperature strength was numerically examined for austenitic heat-resisting Fe-Cr-Ni-N(STS310J1TB) and Fe-Cr-Ni (STS310S) alloys. The solute atmosphere dragging stress of dislocation was calculated in optional dislocation velocity of STS310J1TB and STS310S at $650^{\circ}C$, $675^{\circ}C$ and $700^{\circ}C$. As a result of the numerical calculation, the solute atmosphere dragging stress of STS310J1TB was about 50 times larger than that of STS310S. When the temperature became high, the maximum value of solute atmosphere dragging stress was small and the velocity of moving dislocation was fast. From the relationship between the dislocation rate and the solute atmosphere dragging stress, the relation of both was proportional and the inclination is about 1 in the level with low velocity of moving dislocation. From above results, the mechanism of dislocation movement in STS310J1TB was the solute atmosphere dragging stress. The solute atmosphere dragging stress, which was calculated from the numerical calculation was close to the effect stress in stress relaxation tests.

A Study on Controlling Efflux Sediment Diffusion by Jetty Construction at Small Estuary (소규모 하구에서 토사유출 확산제어에 관한 연구)

  • Park, Sang Kil;Park, Hyun Su;Yoon, Jong Su;Lee, Si Ho
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.5B
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    • pp.483-491
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    • 2009
  • In this study, a jetty construction is taken into account for the reduction of sediment diffusive concentration incoming from the upstream river due to the urbanization and industrial development and to minimize the effects on the coastal ecosystems. The field observation and numerical calculation are conducted to analyze the diffusion zone of sediment concentration in the small estuary and coastal area. The specification of the installed jetty which is able to control the sediment concentration was decided based on the prediction of the dispersion area changes in space and time. The selected size and layout for the jetty design were examined for the dispersion zone by numerical calculation and field observation. As a result, the jetties constructed in the estuary retarded the dispersion rate of sediment concentration, so that the effect area of sediment dispersion was obviously decreased. In addition, the measured field data indicated that the sediment deposition in the inside of dikes could be controlled and the right side area of jetties could be preserved without influx sediment diffusion.

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A Study on the Sensitivity Compensation of Three-dimensional Acoustic Intensity Probe in the Higher Frequency Range (3차원 음향 인텐시티 프로브의 고주파 영역 감도 보상 연구)

  • Kim, Suk-Jae;Hideo, Suzuki;Kim, Chun-Duck
    • The Journal of the Acoustical Society of Korea
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    • v.13 no.5
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    • pp.40-50
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    • 1994
  • In this paper, the sensitivity compensation method for three-dimensional acoustic intensity probe in the higher frequency range has been studied. The measurement error in the higher frequency range is generated from the phase mismatch between microphone's signals of the probe. If the wavelength of sound signal measured is less than those of the distance between microphones of the probe, that is, the higher frequency of the sound signal, the bigger measurement error is generated. In this study, we proposed the compensation methods for one-dimensional acoustic intensity probe with two-microphones, and the efficiency of those methods were investigated by numerical calculation of computer. It was most effective method to compensate the phase mismatch between microphone for the acoustic intensity probe was investigated for the sound estimated. and the efficiency of this method in a three-dimensional probe was investigated for the sound wave travelling in the arbitrary direction by numerical calculation of computer. In this result, the efficiency was proved that, for the measurement error of 1dB or less with the three-dimensional probe of 60mm space, the frequency should be less than 1.2kHz without the error compensation method, but the frequency increased up to 2.8kHz with the error compensation method.

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