• 제목/요약/키워드: wave-energy

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Minimization of Crosstalk by Optimum Synthesis of Profiles of Multiple Coupled Data Transmission Lines on Microstrip (다중결합된 마이크로스트립 데이터 전송로 자태의 최적합성을 통한 누화 최소화)

  • 박의준
    • Journal of the Korean Institute of Telematics and Electronics D
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    • v.35D no.12
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    • pp.1-11
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    • 1998
  • A line profile synthesis method is presented that minimizes the nearest-neighbor crosstalk peak level for high-speed pulse transmission in multi-coupled microstrip signal buses. We adopted the optimization technique for the reflected wave control on bus lines resulting in increasing the average spacing between strip conductors, since in a parallel-conductor bus the crosstalk energy is concentrated at the nearest neighbors of the driven line. The generalized S-matrix technique is applied for the input and output waveform prediction, and crosstalk characteristics of various nonuniform lines synthesized for increasing the average spacing are analyzed by comparing each other. Simulation results demonstrate that the Chebyshev taper with dips is adequate to significantly minimize the crosstalk peak level under the satisfactory waveform integrity since the profile is oriented to evenly reflect significant pulse spectra within the frequency range of pulse.

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3D Simulation of Earthquake Ground Motion Using Locally Variable Time-Step Finite-Difference Method

  • Kang, Tae-Seob;Baag, Chang-Eob
    • Proceedings of the International Union of Geodesy And Geophysics Korea Journal of Geophysical Research Conference
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    • 2003.05a
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    • pp.18-18
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    • 2003
  • Three-dimensional finite-difference simulation of earthquake ground motion is performed using a locally variable time-step (LVTS) scheme matching with discontinuous grids. Discontinuous grids in three directions and extension of the discontinuous grids' boundary to the free-surface in the LVTS scheme minimize the cost of both the computational memory and the CPU time for models like the localized sedimentary basin. A simplified model of sedimentary basin is dealt to show the feasibility and efficiency of the LVTS scheme. The basin parameters are examined to understand the main characteristics on ground-motion response in the basin. The results show that the seismic energy is concentrated on a marginal area of the basin far from the source. This focusing effect is mainly due to the constructive interference of the direct S-wave with the basin-edge induced surface waves. The ground-motion amplification over the deepest part of the basin is relatively lower than that above the shallow basin edge. Therefore the ground-motion amplification may be more related to the source azimuth or the direction of the incident waves into the basin rather than the depth of it.

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HOW TO DEAL WITH RADIO ASTRONOMY INTERFERENCE

  • UMAR, ROSLAN;HAZMIN, SABRI NOR;ABIDIN, ZAMRI ZAINAL;IBRAHIM, ZAINOL ABIDIN
    • Publications of The Korean Astronomical Society
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    • v.30 no.2
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    • pp.691-693
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    • 2015
  • Radio sources are very weak, as they can travel through large distances. Radio sources also have photons with low energies compared to others electromagnetic waves (EM). Microwave photons have a little more energy than radio waves, infrared photons have still more, then visible, ultraviolet, X-rays, and the most energetic electromagnetic wave is gamma-rays. Radio astronomy studies are restricted due to radio frequency interference (RFI) produced by people. If this disturbance is not minimized, it poses critical problems for astrophysical studies. The purpose of this paper is to profile RFI maps in Peninsular Malaysia with a minimum mapping technique for RFI interference. Decision-making processes using GIS (Geographical Information System) for the selection requires gathering information for a variety of parameters. These factors affecting the selection process are also taken into account. In this study, various factors or parameters are involved, such as the availability of telecommunications transmission (including radio and television), rainfall, water lines and human activity. This mapping step must be followed by RFI site testing in order to identify areas of low RFI. This study will benefit radio astronomy research, especially regarding the RFI profile.

Position Estimation of Underwater Acoustic Source Using Pulsed CW Signal (Pulsed CW 신호를 사용하는 수중 음원의 위치 추정을 위한 시간지연차 추정법)

  • 최영근;손권;도경철;김기만
    • The Journal of the Acoustical Society of Korea
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    • v.23 no.7
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    • pp.514-520
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    • 2004
  • There are many techniques for underwater source localization. These are the methods based on TDOA (Time Difference Of Arrival) estimation. beamforming techniques and high resolution techniques, etc. In this Paper we estimate the underwater source position using MCPSP (Modified Cross Power Spectrum Phase) function that is calculated on frequency domain using sensors of small number. However, the performances of the localizing method based on MCPSP function drops greatly in the case of CW (Continuous Wave) signal . In this Paper we proposed the TDOA estimation method for pulsed CW signal. In the Proposed method we composed of new segment including a edge of ping. This segment was computed by short-time energy detection. With theoretical representation the performances of the proposed method were analyzed under various environment.

Numerical investigation on the performance of the aluminized HMX with varying aluminum concentration (알루미늄 함유량 변화에 따른 알루미늄 입자가 함유된 HMX 성능에 관한 수치 연구)

  • Kim, Wuhyun;Gwak, Min-cheol;Yoh, Jai-ick
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2017.05a
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    • pp.617-621
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    • 2017
  • The performance characteristics of aluminized high explosive are considered by varying the aluminum(Al) concentration in a two-phase model. Since the time scales of the characteristic combustion process of high explosives and Al particles differ, the process of energy release behind the leading detonation wave front occurs over an extended period of time. Two cardinal observations are reported: a decrease in detonation velocity with an increase in Al concentration and a double front detonation (DFD) feature when anaerobic Al reaction occurs behind the front. In the current study, a series of confined rate sticks are considered for characterizing the performance of aluminized HMX with a maximum Al concentration of 50%. The simulated results are compared with the experimental data for 5%-25% concentrations.

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Characteristics of Temperature Variation to the Piezoelectric Bimorph for Vortex Flowmeter (와류 유량센서용 압전 바이몰프의 온도변화에 따른 특성)

  • Lee, Guen-Taek;Kim, Hyung-Sun;Im, Jong-In
    • Korean Journal of Materials Research
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    • v.17 no.5
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    • pp.289-292
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    • 2007
  • Although piezoelectric bimorph that is using as the sensor in medical and industrial measurement has large displacement, it has problems including efficiency in generating force, energy convergence, and response. Its application is being limited based on the change in resonance frequency with temperature. In this study, to overcome the disadvantages, PZT piezoelectric ceramics was prepared and produced a parallel type piezoelectric bimorphs. In addition, by using the finite element method. the configuration of piezoelectric bimorph was designed and the displacement of the bimorph based on applied electric pressure and the wave pattern were measured. By analyzing the resonance characteristics of the bimorph in the temperature range of $-60{\sim}80^{\circ}C$, an attempt was made to study the operational characteristics and temperature reliability of vortex flowmeter sensor. As a result, the resonance frequency of the bimorph was gradually increased with the temperature from $-60{\sim}80^{\circ}C$. The deflection of the bimorph was found to strongly depend on both the applied electric field waveform and the environmental temperature.

Electronic States Calculation of Fe4N by DV-Xα cluster calculation (DV-Xα 클러스터 계산법에 의한 Fe4N의 전자상태계산)

  • Song, Dong-Won;Lee, In-Seop;Bae, Dong-Su
    • Korean Journal of Materials Research
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    • v.12 no.1
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    • pp.44-47
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    • 2002
  • DV(Discrete Variation)-X${\alpha}$ cluster calculation was employed to calculate the electronic states of ${\gamma}'- Fe_4N$ which was one of iron nitride phases synthesized from plasma ion nitriding to improve surface hardness and wear resistance. The result of calculated electron density of states for Fe was similar to the result of band calculation. The cluster used for calculation of electronic states of ${\gamma}'-Fe_4N$ was based on $Fe_{14}N$ cluster which comprises 15 atoms. Finally the electronic states of ${\gamma}'- Fe_4N$ such as net-charge, band order, energy level, electron wave-function, and contour map for electron density were derived by the calculation.

Simulation of Two-Dimensional Intervalley Scattering Rate in HEMT Device (HEMT 소자의 2차원 계곡간 산란율 시뮬레이션)

  • 이준하;이흥주
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.5 no.4
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    • pp.336-339
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    • 2004
  • In this paper the two-dimensional scattering rates were calculated in pseudomorphic Al/sub x//Ga/sub 1-x//As/Ga/sub y/In/sub l -y//As/GaAs heterostructure systems. The electronic states of the square quantum well were determined by the numerical self-consistent solution of Poisson's and Schrodinger's equations. The numerically obtained wave functions and energy levels were used to obtain the major two-dimensional scattering rates in this structure. Polar optical- and acoustic-phonon scattering, piezoelectric, ionized impurity and alloy scattering were considered for the first two sub-bands. The results were compared to the three-dimensional scattering rates also calculated in the same region.

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Brightness Characteristics by Applied Frequency for External Electrode Fluorescent Lamp (외부전극형 형광램프의 입력 주파수에 따른 휘도 특성)

  • Choi, Yong-Sung;Cha, Jae-Chea;Lee, Kyung-Sup
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2006.12a
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    • pp.75-78
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    • 2006
  • An external electrode fluorescent lamps (EEFLs) have the advantage of a long lifetime in the early stages of the study on plasma discharge, interest in the lamp continues. Studies on the operation of external electrode fluorescent lamps have focused mainlyon its use of a type of high frequency (MHz). By performing high brightness using a square wave operation method with the low frequency below 100kHz, which is applied to a narrowed tube type lamp that has several mm of lamp diameter, an EEFL presented the possibility of using it as a light source for backlights. However, because an EEFL generates plasma using wall charges, which considers the impedance characteristics of glass based on the structural principle in discharge, it can be significantly affected by frequency. Thus, this study verifies the change in the characteristics of electromagnetic fields according to the change in frequency through a Maxwell's electromagnetic field simulation and examines the relationship between the change in the EEFL frequency and brightness by measuring the optical. characteristics. In addition, the characteristics of the transformation of energy orbits were verified by investigating the characteristics of the wavelength according to the change in frequency through the OES.

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A Study on Degradation Pattern of GIS Using Clustering Methode (군집화 기법을 이용한 GIS 열화 패턴 연구)

  • Lee, Deok Jin
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.31 no.4
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    • pp.255-260
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    • 2018
  • In recent years, increasing electricity use has led to considerable interest in green energy. In order to effectively supply, cut off, and operate an electric power system, many electric power facilities such as gas insulation switch (GIS), cable, and large substation facilities with higher densities are being developed to meet demand. However, because of the increased use of aging electric power facilities, safety problems are emerging. Electromagnetic wave and leakage current detection are mainly used as sensing methods to detect live-line partial discharges. Although electromagnetic sensors are excellent at providing an initial diagnosis and very reliable, it is difficult to precisely determine the fault point, while leakage current sensors require a connection to the ground line and are very vulnerable to line noise. The partial discharge characteristic in particular is accompanied by statistical irregularity, and it has been reported that proper statistical processing of data is very important. Therefore, in this paper, we present the results of analyzing ${\Phi}-q-n$ cluster distributions of partial discharge characteristics by using K-means clustering to develop an expert partial discharge diagnosis system generated in a GIS facility.