• Title/Summary/Keyword: Reducing Parameter

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BER Performance of OFDM Combined with TDM Using Frequency-Domain Equalization

  • Gacanin, Haris;Takaoka, Shinsuke;Adachi, Fumiyuki
    • Journal of Communications and Networks
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    • v.9 no.1
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    • pp.34-42
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    • 2007
  • Orthogonal frequency division multiplexing (OFDM) combined with time division multiplexing (TDM), in this paper called OFDM/TDM, can overcome the high peak-to-average-power ratio (PAPR) problem of the conventional OFDM and improve the robustness against long time delays. In this paper, the bit error rate (BER) performance of OFDM/FDM in a frequency-selective Rayleigh fading. channel is evaluated by computer simulation. It is shown that the use of frequency-domain equalization based on minimum mean square error criterion (MMSE-FDE) can significantly improve the BER performance, compared to the conventional OFDM, by exploiting the channel frequency-selectivity while reducing the PAPR or improving the robustness against long time delays. It is also shown that the performance of OFDM/FDM designed to reduce the PAPR can bridge the conventional OFDM and single-carrier (SC) transmission by changing the design parameter.

Affect of Flow Condition on Formation of Flameless Combustion (무화염 형성에 영향을 미치는 유동조건에 대한연구)

  • Hong, Seong Weon;Lee, Pil Hyong;Cha, Chun Loon;Song, Ki Jong;Im, Hyun Jin;Hwang, Sang Soon
    • 한국연소학회:학술대회논문집
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    • 2012.04a
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    • pp.189-192
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    • 2012
  • The flameless combustion has been considered as one of the promising combustion technology for high energy efficiency and reducing NOx and CO emissions. To investigate the effects of fluid conditions on the formation of flameless combustion, a numerical approach was performed. The flameless combustion possesses lower temperature region and more uniform temperature distribution than conventional flame. The results show that the flow rate of the system which mainly influence on recirculation ratio is the most important parameter for flameless combustion.

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Modulation of Impedance Parameters for a Teleoperator Using Distance Measurement (거리센서를 이용한 원격 조종 장치의 임피던스 변조)

  • 송지혁;박종현;김상철
    • 제어로봇시스템학회:학술대회논문집
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    • 2000.10a
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    • pp.84-84
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    • 2000
  • This paper proposes a new impedance control scheme based on a variable stiffness matrix for a bilateraL teleoperation. In this scheme, stiffness matrix of the impedance model in the slave is modulated based on the distance, measured by an ultrasonic sensor, between the slave and environment. At the same time, the stiffness matrix of the master is also changed accordingly in order for the impedance parameters of the combined system to remain constant The proposed scheme is implemented on a 1-dof master/slave system to perform a simple task. In the experiments, the teleoperator with the impedance parameter modulation shows better performance than one with fixed impedance parameters, especially in reducing task execution time and in avoiding excessive external forces.

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Resolution Enhancement of Ultrasonic B-scan Images by Modified Wiener Filter (변형된 Wiener 필터를 이용한 초음파 B스캔영상의 해상력 향상)

  • 정준영;진영민
    • Journal of Biomedical Engineering Research
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    • v.11 no.1
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    • pp.113-120
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    • 1990
  • In this paper, the deconvolution method utilizing a modified Wiener filter is applied for the enhancement of lateral resolution of ultrasonic B-scan Images. For this purpose, a phantom composed of wires which are 0.6mm of diameter and apart in the range between 3 to 9mm is constructed. The modified Wiener filter with optimal parameter is applied to the phantom for the analysis of ultrasonic image. The results obtained are as follows'When all parameters of the modified Wiener filter are optimal, the resolution of B-scan images is enhanced by 50 percent : Othenrise, the images are blurred, spilt at peak points, or noises are strengthened severely. When the point-spread function representing the characteristic function of the system is determined, the selection ranges of op- timum parameters may be narrowed. It is expected that the proposed method may be able to apply to clinic situations for more accurate image analysis by means of reducing the loss of important information.

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The MMAP/M/c System with Heterogeneous Servers and Retrial

  • Kim Che Soong;Kim Ji Seung
    • Proceedings of the Korean Society for Quality Management Conference
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    • 2004.04a
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    • pp.499-502
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    • 2004
  • Multi-server Markovian retrial model with heterogeneous servers is analyzed. Arriving customers constitute the MMAP(Marked Markovian Arrival Process). Distribution of the primary customers among the servers is performed randomly depending on the type of a customer and the number of the server. Customers from the orbit have the exponential service time distribution with a parameter depending on the server only. The choice of the server for a retrial is made randomly as well. Multidimensional continuous time Markov chain describing operation of the model is investigated by means of reducing to asymptotically quasi-toeplitz Markov chaius.

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Friction Characteristics of Micro-scale Dimple Pattern under Mixed and Hydrodynamic Lubrication Condition (혼합 및 유체윤활하에서 Micro-Scale Dimple Pattern의 마찰특성)

  • Chae Young-Hun;Kim Seock-Sam
    • Journal of the Korean Society for Precision Engineering
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    • v.22 no.2
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    • pp.188-193
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    • 2005
  • Surface texturing of tribological application is another attractive technology of friction reducing. Also, reduction of friction is therefore considered to be a necessary requirement for improved efficiency of machine. In this paper attempts to investigate the effect of density for micro-scale dimple pattern on bearing steel flat mated with pin-on-disk. We demonstrated the lubrication mechanism for a Stribeck curve, which has a relationship between the friction coefficient and a dimensionless parameter for lubrication condition. It is found that friction coefficient is depended on the density of surface pattern. It was thus verified that micro-scale dimple could affect the friction reduction considerably under mixed and hydrodynamic lubrication conditions from based on friction map. Lubrication condition regime has an influence on the friction coefficient induced the density of micro dimple.

Finite Element analysis of Acoustic Behavior of Absorbent Materials with experimental Verification (유한요소법에 의한 흡음재 음향특성 연구 및 검증)

  • 정환익;김관주;박진규;김상헌
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.11a
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    • pp.874-878
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    • 2003
  • Acoustic materials are used for the purpose of absorbing noise and reducing transmission of sound into the receiving room. The purpose of this research is to predict the performance of absorbent materials with respect to absorbing behavior and transmission loss as possible as accurately. The performance of the absorbent materials are carried out systematically as follows: The Biot parameter are measured, first. Then using above parameters as input, LMS's SYSNOISE and VIOLINS programs are used to predict absorption coefficient and transmission loss values, which magnitudes are compared with experimental results. As an sample acoustic material, SK SKY VIVA and PET are selected.

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DESIGN OF ADAPTIVE CONTROLLER OF DC SERVO MOTOR (직류전동기의 적응 제어기 설계에 관한 연구)

  • Chang, S.G.;Won, J.S.
    • Proceedings of the KIEE Conference
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    • 1987.11a
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    • pp.25-28
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    • 1987
  • Design procedure of adaptive controller with variable load condition is present and applied to velocity control of small, permanent magnet DC servo motor. The state feedback control scheme is adopted and Recursive Least Squares algorithm is used for parameter estimation. In order to reduce the time consuming. In the procedure of adaptation-gain tuning of state feedback controller, approximate curve fitting technique is applied to the relations between load condition and poles of the system, load condition and feedback gains. With this method, fast adaptation can be accomplished. It is shown that this procedure can be applied not only to variable load condition but also to variation of other system constants, for example variation of resistance and inductance etc.. Simulation results is present for both cases - variable inertia load, variable motor resistance to verify performance improvements. This design procedure produces an adaptive con troller which is feasible for implementation with microprocessor by reducing calculation time.

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New Density-Independent Model for Measurement of Grain Moisture Content using Microwave Techniques

  • Kim, Jong-Heon;Kim, Ki-Bok;Noh, Sang-Ha
    • Journal of Electrical Engineering and information Science
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    • v.2 no.4
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    • pp.72-78
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    • 1997
  • A free space transmission method using standard gain horn antennas in the frequency range from 9.0 to 10.5GHz is applied to determine the dielectric properties of grain such as rough rice ,brown rice and barley. The dielectric constant and loss factor, which depend on the moisture content of the wetted grain are obtained from the measured attenuation and phase shift by vector network analyzer. The moisture content of grain varied from 11 to 25% based on this wetted condition. The measured values of dielectric constants as a function of moisture density are compared with values of those obtained using he predicted model for estimating dielectric constants of grain. The effect of density fluctuation, high is an important parameter governing the dielectric properties of grain, on the dielectric constant and loss factor is presented. A new density-independent model in terms of measured attenuation an moisture density is proposed of reducing the effects of density fluctuation on the moisture content measurement.

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Calculation of Force Density in Linear Motor Using Equivalent Magnetic Circuit (등가자기회로를 이용한 리니어모터의 추력밀도계산)

  • Hong, Jung-Pyo;Kang, Do-Hyun;Joo, Soo-Won;Hahn, Sung-Chin
    • Proceedings of the KIEE Conference
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    • 2001.04a
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    • pp.96-98
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    • 2001
  • In this paper, the equivalent magnetic circuit and FEM are used to calculate force density of linear BLDC motor. The equivalent magnetic circuit is hard to exact compose for analysis model and it is just applied to linear system. To flexible design and reducing the calculated and analyzed time, magnetic circuit has to be used for designing the linear BLDC motor and deducing equation of force density. Force density as parameter of permanent magnet and coil-side width that are important to determined force density can be estimated using equation of force density. FEM is used to prove reliability of equation of force density and to consider the nonlinear system. Equivalent magnetic circuit and result of FEM are similar, but it is little different by friction loss at the experiment.

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