• Title/Summary/Keyword: Synthetic method

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New Circular Wave Generation Method for Synthetic Focusing in Ultrasonic Imaging Systems (초음파 영상 시스템에서 합성 집속을 위한 새로운 구면파 발생 방법)

  • Ahn, Young-Bok
    • Journal of Biomedical Engineering Research
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    • v.28 no.6
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    • pp.798-802
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    • 2007
  • The synthetic focusing in the ultrasonic imaging systems has been formed in the way that one element transmits a circular wave and receives an echo signal. The amplitude of the signal transmitted from one element is too small to propagate a long distance so that the SNR(Signal to Noise Ratio) is very low in an image obtained by the synthetic focusing. To solve this problem, a defocusing method which uses several elements has been proposed. In this method, the SNR is improved due to using several elements to transmit the circular wave. But if the number of transmitting elements increases, the phase distortion is severe in the defocusing method. In this paper, we propose a new method that can generate a circular wave using a lot of elements without phase distortion. At first, we generate limited plane waves with different propagation angles and then superpose them to make a circular wave. We show that the circular wave can be used to improve SNR in the real-time 3D ultrasonic imaging as well as the synthetic focusing through computer simulation and experiments.

Efficent Synthetic Method of Obtaining Oligosaccharide Units and Derivatives Utilizing Endoglycosidases

  • Murata, Takeomi;Usui, Taichi
    • Biotechnology and Bioprocess Engineering:BBE
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    • v.7 no.5
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    • pp.263-267
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    • 2002
  • Our purpose is to develop an efficient synthetic method of obtaining oligosaccharide unit in sufficient amounts to study functions of glycans. Many exoglycosidases have been used as tools for the oligosaccharide synthesis. In contrast, a limited number of reports are available on the utilization of endoglycosidases. We describe herewith the efficient synthetic method of useful oligosaccharides and derivatives as biomaterials utilizing lysozyme, cellulase, and lacto-N-biosidase-mediated transglycosyltions.

Detecting location of reinforcing bars in concrete using synthetic aperture radar method (합성개구 레이더법에 의한 콘크리트 내 철근위치 산정)

  • Park, Seok-Kyun
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.05a
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    • pp.602-605
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    • 2006
  • Locating reinforcing bars, in particular to know their accurate depths and horizontal distances, is very important in radar inspection of concrete structures. By the way, it is not easy for an accurate depth and horizontal distance estimation of reinforcing bars in concrete structures by the radar test. This problem can be solved by synthetic aperture radar method. To improve the vertical and horizontal resolution of reinforcing bars in concrete, synthetic aperture radar method was examined in this study.

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FINDING COSMIC SHOCKS: SYNTHETIC X-RAY ANALYSIS OF A COSMOLOGICAL SIMULATION

  • HALLMAN ERIC J.;RYU DONGSU;KANG HYESUNG;JONES T. W.
    • Journal of The Korean Astronomical Society
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    • v.37 no.5
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    • pp.593-596
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    • 2004
  • We introduce a method of identifying evidence of shocks in the X-ray emitting gas in clusters of galaxies. Using information from synthetic observations of simulated clusters, we do a blind search of the synthetic image plane. The locations of likely shocks found using this method closely match those of shocks identified in the simulation hydrodynamic data. Though this method assumes nothing about the geometry of the shocks, the general distribution of shocks as a function of Mach number in the cluster hydrodynamic data can be extracted via this method. Characterization of the cluster shock distribution is critical to understanding production of cosmic rays in clusters and the use of shocks as dynamical tracers.

A STUDY ABOUT FLOW CONTROL CHARACTERISTICS USING A SYNTHETIC JET (Synthetic Jet을 이용한 유동제어 특성연구)

  • Hong, Woo-Ram;Kim, Sang-Hoon;Kim, Woo-Re;Kim, Yu-Shin;Kim, Chong-Am
    • Journal of computational fluids engineering
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    • v.12 no.2
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    • pp.1-7
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    • 2007
  • To develop an aerodynamic performance, two groups of studies have been achieved widely. One is about the geometric design of vehicles and the other is about aerodynamic devices. Geometric design is a credible and stable method. However, it is not flexible and each part is related interactively. Therefore, if one part of geometry is modified, the other part will be required to redesign. On the other hand, the flow control by aerodynamic devices is flexible and modulized method. Even though it needs some energy, a relatively small amount of input makes more advanced aerodynamic performance. Synthetic jet is one of the method in the second group. The device repeats suctions and blowing motions in constant frequency. According to the performance, the adjacent flow to flight surface are served momentum. This mechanism can reduce the aerodynamic loss of boundary layer and separated flow. A synthetic jet actuator has several parameters, which influences the flow control. This study focuses on the parameter effects of synthetic jet - orifice geometry, frequency, jet speed and etc.

STUDY OF FLOW CONTROL CHARACTER USING SYNTHETIC JET (Synthetic jet을 이용한 유동제어 특성연구)

  • Hong, Woo-Ram;Kim, Sang-Hoon;Kim, Woo-Re;Kim, Yu-Shin;Kim, Chong-Am
    • 한국전산유체공학회:학술대회논문집
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    • 2007.04a
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    • pp.72-78
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    • 2007
  • To develop the aerodynamic performance, there are widely two group of studies are achieved. The first one is about design of the vehicles geometry and the second one is about aerodynamic devices. Geometry design is highly credible and stable method. But it is not flexible and each parts are related interactively. So if one part geometry are modified, the other parts are required to be redesigned. The other hand, flow control by aerodynamic device is flexible and modulized method. Though it needs energy, relatively little input makes far advanced aerodynamic performance. Synthetic Jet is one of the second group method. The device repeats suction and blowing motion in constant frequency. According to the performance, the flow which are near the flight surface are served momentum. This mechanism can reduce the aerodynamic loss by boundary layer and separated flow. Synthetic jet actuator has several parameters, that influence the flow control. This study focus the parameters effects of the synthetic jet - orifice geometry, frequency, jet speed and etc.

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Synthetic data generation by probabilistic PCA (주성분 분석을 활용한 재현자료 생성)

  • Min-Jeong Park
    • The Korean Journal of Applied Statistics
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    • v.36 no.4
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    • pp.279-294
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    • 2023
  • It is well known to generate synthetic data sets by the sequential regression multiple imputation (SRMI) method. The R-package synthpop are widely used for generating synthetic data by the SRMI approaches. In this paper, I suggest generating synthetic data based on the probabilistic principal component analysis (PPCA) method. Two simple data sets are used for a simulation study to compare the SRMI and PPCA approaches. Simulation results demonstrate that pairwise coefficients in synthetic data sets by PPCA can be closer to original ones than by SRMI. Furthermore, for the various data types that PPCA applications are well established, such as time series data, the PPCA approach can be extended to generate synthetic data sets.

A computational approach to the simulation of controlled flows by synthetic jets actuators

  • Ferlauto, Michele;Marsilio, Roberto
    • Advances in aircraft and spacecraft science
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    • v.2 no.1
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    • pp.77-94
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    • 2015
  • The paper focuses on the integration of a non-linear one-dimensional model of Synthetic Jet (SJ) actuator in a well-assessed numerical simulation method for turbulent compressible flows. The computational approach is intended to the implementation of a numerical tool suited for flow control simulations with affordable CPU resources. A strong compromise is sought between the use of boundary conditions or zero-dimensional models and the full simulation of the actuator cavity, in view of long-term simulation with multiple synthetic jet actuators. The model is integrated in a multi-domain numerical procedure where the controlled flow field is simulated by a standard CFD method for compressible RANS equations, while flow inside the actuator is reduced to a one-dimensional duct flow with a moving piston. The non-linear matching between the two systems, which ensures conservation of the mass, momentum and energy is explained. The numerical method is successfully tested against three typical test cases: the jet in quiescent air, the SJ in cross flow and the flow control on the NACA0015 airfoil.

A Reduction of Grating Lobe By Using the Multi-element Receive Synthetic Focusing In Ultrasonic Image (초음파 영상에서 Multi-element Receive Synthetic Focusing을 이용한 그레이팅 로브 감축)

  • Lee, J.S.;Ahn, Y.B.
    • Proceedings of the KOSOMBE Conference
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    • v.1997 no.11
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    • pp.559-562
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    • 1997
  • In this paper, we propose the method that reduce the grating lobe in the ultrasound synthetic focusing images. synthetic focusing images have more larger and closer grating lobe than conventional phased array images and more lower signal to noise ratio. so, we represent the method that reduce the grating lobe by using multi element receive focusing. experimental results are showed that the proposed multi element receiving method reduce the grating lobe and increase the signal to noise ratio.

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The Effects of Border Shutdowns on the Spread of COVID-19

  • Kang, Nahae;Kim, Beomsoo
    • Journal of Preventive Medicine and Public Health
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    • v.53 no.5
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    • pp.293-301
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    • 2020
  • Objectives: At the beginning of the coronavirus disease 2019 (COVID-19) pandemic, some countries imposed entry bans against Chinese visitors. We sought to identify the effects of border shutdowns on the spread of the COVID-19 outbreak. Methods: We used the synthetic control method to measure the effects of entry bans against Chinese visitors on the cumulative number of confirmed cases using World Health Organization situation reports as the data source. The synthetic control method constructs a synthetic country that did not shut down its borders, but is similar in all other aspects. Results: Six countries that shut down their borders were evaluated. For Australia, the effects of the policy began to appear 4 days after implementation, and the number of COVID-19 cases dropped by 94.4%. The border shutdown policy took around 13.2 days to show positive effects and lowered COVID-19 cases by 91.7% on average by the end of February. Conclusions: The border shutdowns in early February significantly reduced the spread of the virus. Our findings are informative for future planning of public health policies.