• Title/Summary/Keyword: line source model

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Kinematic Approximation of Partial Derivative Seismogram with respect to Velocity and Density (편미분 파동장을 이용한 탄성파 주시 곡선의 평가)

  • Shin, Chang-Soo;Shin, Sung-Ryul
    • Geophysics and Geophysical Exploration
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    • v.1 no.1
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    • pp.8-18
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    • 1998
  • In exploration seismology, the Kirchhoff hyperbola has been successfully used to migrate reflection seismo-grams. The mathematical basis of Kirchhoff hyperbola has not been clearly defined and understood for the application of prestack or poststack migration. The travel time from the scatterer in the subsurface to the receivers (exploding reflector model) on the surface can be a kinematic approximation of Green's function when the source is excited at position of the scatterer. If we add the travel time from the source to the scatterer in the subsurface to the travel time of exploding reflector model, we can view this travel time as a kinematic approximation of the partial derivative wavefield with respect to the velocity or the density in the subsurface. The summation of reflection seismogram along the Kirchhoff hyperbola can be evaluated as an inner product between the partial derivative wavefield and the field reflection seismogram. In addition to this kinematic interpretation of Kirchhoff hyperbola, when we extend this concept to shallow refraction seismic data, the stacking of refraction data along the straight line can be interpreted as a measurement of an inner product between the first arrival waveform of the partial derivative wavefield and the field refraction data. We evaluated the Kirchhoff hyperbola and the straight line for stacking the refraction data in terms of the first arrival waveform of the partial derivative wavefield with respect to the velocity or the density in the subsurface. This evaluation provides a firm and solid basis for the conventional Kirchhoff migration and the straight line stacking of the refraction data.

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Enhancement of Interface Flow Limit using Static Synchronous Series Compensators

  • Kim Seul-Ki;Song Hwa-Chang;Lee Byoung-Jun;Kwon Sae-Hyuk
    • Journal of Electrical Engineering and Technology
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    • v.1 no.3
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    • pp.313-319
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    • 2006
  • This paper addresses improving the voltage stability limit of interface flow between two different regions in an electric power system using the Static Synchronous Series Compensator (SSSC). The paper presents a power flow analysis model of a SSSC, which is obtained from the injection model of a series voltage source inverter by adding the condition that the SSSC injection voltage is in quadrature with the current of the SSSC-installed transmission line. This model is implemented into the modified continuation power flow (MCPF) to investigate the effect of SSSCs on the interface flow. A methodology for determining the interface flow margin is simply briefed. As a case study, a 771-bus actual system is used to verify that SSSCs enhance the voltage stability limit of interface flow.

Digital Active Noise Control System Used Inverse Model (역모델을 이용한 디지털 능동 소음제어 시스템)

  • 정찬수;이강욱;정양응
    • The Journal of the Acoustical Society of Korea
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    • v.11 no.1E
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    • pp.56-63
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    • 1992
  • The poblem of active oise control has been analysed using a adaptive signal processing technique. In this methods, the adaptive signal processor or model predicts the primary sound wave travelling along the acoustic plant and generates the secondary source 180° out of phase which attempts to attempts to attenuate the undesired noise by destructive interference. In the solutions presented here, acoustic propagation delay is considered as a part of the model which used the FIR filter. The effects of error path and auxiliary path transfer functioin are anayzed and a new on=-line technique for error path modeling, adaptive delayed inverse modeling is presented. In this study, using these new concepts, our system can more reduce the noise level in duct to 5dB-15dB than only using LMS algorithm system.

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A Study on Clutch-disc Characteristics for the Torsional Vibration Reduction of the Drive-Line at Creeping (최저속주행시 동력전달계의 비틀림진동 저감을 위한 클러치특성 연구)

  • Chung, T.J.;Hong, D.P.;Kim, S.S.;Kim, S.S.
    • Transactions of the Korean Society of Automotive Engineers
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    • v.3 no.2
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    • pp.102-111
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    • 1995
  • The non-periodic fluctuation of the engine torque appears to be the major source of the torsional vibration of the automotive driveline. The reduction of this torsional vibration has become a significant problem along with the requirements of higher performance. The torsional vibration of the automotive driveline can be reduced by smoothing the fluctuation by adjusting the torsional characteristics of the clutch-disc. Computer simulation of the driveline is a useful investigative tool on studying the torsional characteristics of the clutch-disc. In this paper, a dynamic model for the automotive driveline was developed, and the engine torque of the model were evaluated with experimental data. By executing a simulation using the model, it has become possible to obtain the clutch-disc torsional characteristics for reducting the torsional vibration at creeping.

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Analysis of a Harmonics Neutralized 48-Pulse STATCOM with GTO Based Voltage Source Converters

  • Singh, Bhim;Saha, Radheshyam
    • Journal of Electrical Engineering and Technology
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    • v.3 no.3
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    • pp.391-400
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    • 2008
  • Multi-pulse topology of converters using elementary six-pulse GTO - VSC (gate turn off based voltage source converter) operated under fundamental frequency switching (FFS) control is widely adopted in high power rating static synchronous compensators (STATCOM). Practically, a 48-pulse ($6{\times}8$ pulse) configuration is used with the phase angle control algorithm employing proportional and integral (PI) control methodology. These kinds of controllers, for example the ${\pm}80MVAR$ compensator at Inuyama switching station, KEPCO, Japan, employs two stages of magnetics viz. intermediate transformers (as many as VSCs) and a main coupling transformer to minimize harmonics distortion in the line and to achieve a desired operational efficiency. The magnetic circuit needs altogether nine transformers of which eight are phase shifting transformers (PST) used in the intermediate stage, each rating equal to or more than one eighth of the compensator rating, and the other one is the main coupling transformer having a power rating equal to that of the compensator. In this paper, a two-level 48-pulse ${\pm}100MVAR$ STATCOM is proposed where eight, six-pulse GTO-VSC are employed and magnetics is simplified to single-stage using four transformers of which three are PSTs and the other is a normal transformer. Thus, it reduces the magnetics to half of the value needed in the commercially available compensator. By adopting the simple PI-controllers, the model is simulated in a MATLAB environment by SimPowerSystems toolbox for voltage regulation in the transmission system. The simulation results show that the THD levels in line voltage and current are well below the limiting values specified in the IEEE Std 519-1992 for harmonic control in electrical power systems. The controller performance is observed reasonably well during capacitive and inductive modes of operation.

Emission Characteristics of Elemental Constituents in Fine Particulate Matter Using a Semi-continuous Measurement System (준 실시간 측정시스템을 이용한 미세입자 원소성분 배출특성 조사)

  • Park, Seung-Shik;Ondov, John M.
    • Journal of Korean Society for Atmospheric Environment
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    • v.26 no.2
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    • pp.190-201
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    • 2010
  • Fine particulate matter < $1.8{\mu}m$ was collected as a slurry using the Semicontinuous Elements in Aerosol Sampler with time resolution of 30-min between May 23 and 27, 2002 at the Sydney Supersite, Florida, USA. Concentrations of 11 elements, i.e., Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Se, and Zn, in the collected slurry samples were determined off-line by simultaneous multi-element graphite furnace atomic absorption spectrometry. Temporal profiles of $SO_2$ and elemental concentrations combined with meteorological parameters such as wind direction and wind speed indicate that some transient events in their concentrations are highly correlated with the periods when the plume from an animal feed supplement processing facility influenced the Sydney sampling site. The peaking concentrations of the elemental species during the transient events varied clearly as the plume intensity varied, but the relative concentrations for As, Cr, Pb, and Zn with respect to Cd showed almost consistent values. During the transient events, metal concentrations increased by factors of >10~100 due to the influence of consistent plumes from an individual stationary source. Also the multi-variate air dispersion receptor model, which was previously developed by Park et al. (2005), was applied to ambient $SO_2$ and 8 elements (Al, As, Cd, Cr, Cu, Fe, Pb, and Zn) measurements between 20:00 May 23 and 09:30 May 24 when winds blew from between 70 and $85^{\circ}$, in which animal feed processing plant is situated, to determine emission and ambient source contributions rates of $SO_2$ and elements from one animal feed processing plant. Agreement between observed and predicted $SO_2$ concentrations was excellent (R of 0.99; and their ratio, $1.09{\pm}0.35$) when one emission source was used in the model. Average ratios of observed and predicted concentrations for As, Cd, Cr, Pb, and Zn varied from $0.83{\pm}0.26$ for Pb to $1.12{\pm}0.53$ for Cd.

The Analysis of the effects of the platform screen door on the fire driven flow in The Deeply Underground Subway Station (대심도 지하역사에서의 화재시 플랫폼 스크린 도어에 의한 열, 연기 거동 영향 분석)

  • Jang, Y.J.;Kim, H.B.;Lee, C.H.;Jung, W.S.
    • Proceedings of the KSME Conference
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    • 2008.11b
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    • pp.1984-1989
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    • 2008
  • In this study, fire simulations were performed to analyze the characteristics of the fire driven flow and the effects of the platform screen door on the smoke flow in the station, when the fire occurred in the center of the platform. Soongsil Univ. station (line number 7, 47m in depth underground) was chosen which was the one of the deepest underground subway stations in the Seoul metro, SMRT. The parallel computational method was employed to compute the heat and mass transfer eqn's with 6 CPUs of the linux clustering machine. The fire driven flow was simulated with using FDS code in which LES method was applied. The Heat release rate was 10MW and The Ultrafast model was applied for the growing model of the fire source. The 10,000,000 structured grids were used.

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A Study of Seam Tracking by Arc Sensor Using Current Area Difference Method (전류 면적차를 이용한 아크 센서의 용접선 추적에 관한 연구)

  • 김용재;이세헌;엄기원
    • Journal of Welding and Joining
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    • v.14 no.6
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    • pp.131-139
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    • 1996
  • The response of the arc sensor using the welding current and/or welding voltage as its outputs has been obtained by the analysis and/or experiments of the static characteristics of arc sensor. But in order to improve the reliability of arc sensor, it is necessary to know its dynamic characteristics. So in this paper, it is presented the dynamic model of arc sensor including the power source, arc voltage, electrode burnoff rate, and wire feed rate. A numerical simulation of the dynamic model of arc sensor was implemented, computing the welding current with input of CTWD. The results of computer simulations and experiments of $CO_2$arc welding showed that a linear relationship between weaving center - weld line distance and current area difference was established. Additionally, a real-time weld seam tracking system interfaced with industrial welding robot was constructed, the result of the weld seam tracking experiment for weld line with an initial offset error of 5$^{\circ}$was good.

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Modeling of Piano Sound Using Method of Line-Segment Approximation and Curve Fitting (선분 근사법과 곡선의 적합성을 이용한 피아노 음의 모델링)

  • Lim, Hun;Chong, Ui-Pil
    • The Journal of the Acoustical Society of Korea
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    • v.19 no.3
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    • pp.86-91
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    • 2000
  • In this paper, we will discuss the characteristics of the magnitude and the phase of the piano sound in frequency domain by using the FFT(Fast Fourier Transform). The method deciding the parameters representing those sounds through the mathematical model is described. We used the curve fitting method for the modeling of the harmonic part of the sound including the fundamental frequency in order to minimize the errors between original sounds and modeled sounds. furthermore, we used the line segment approximation method for the modeling of the noise part around fundamental frequency. We also applied the same method for the phase model and could get the modeled sound to be similar to the original sound using the parameters. Therefore the high compression ratio comparing the modeled sound to the original sound is achieved.

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A Comparative Study on the Effect of SSSC and UPFC in Static Analysis of Power Systems (전력계통의 정태해석에 미치는 SSSC와 UPFC의 영향에 대한 비교 연구)

  • Kim, Deok-Young;Cho, Eon-Jung;Lee, Kun-Jae;Lee, Ji-Yeol
    • Proceedings of the KIEE Conference
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    • 2001.07a
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    • pp.155-157
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    • 2001
  • This paper presents an comparative study on the effect of SSSC and UPFC to the power system static analysis. SSSC is used to control active power flow in transmission lines by controlling the phase angle of the injected voltage source which is in rectangular to the line current. UPFC is used to control the magnitude and phase of the injected voltage sources which are connected both in series and in parallel with the transmission line to control power flow and bus voltage. To compare the effect of SSSC and UPFC in power system static analysis, the PSS/E simulation program is used. As the FACTS device model such as SSSC and UPFC is not provided in PSS/E yet, an equivalent load model is used. This procedure is implemented by IPLAN which is an external macro program of PSS/E. The simulation results show that UPFC is more effective to improve bus voltage than SSSC in power system static analysis.

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