• Title/Summary/Keyword: Simulation-X$^{(R)}$

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On the computation of low-subsonic turbulent pipe flow noise with a hybrid LES/LPCE method

  • Hwang, Seungtae;Moon, Young J.
    • International Journal of Aeronautical and Space Sciences
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    • v.18 no.1
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    • pp.48-55
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    • 2017
  • Aeroacoustic computation of a fully-developed turbulent pipe flow at $Re_{\tau}=175$ and M = 0.1 is conducted by LES/LPCE hybrid method. The generation and propagation of acoustic waves are computed by solving the linearized perturbed compressible equations (LPCE), with acoustic source DP(x,t)/Dt attained by the incompressible large eddy simulation (LES). The computed acoustic power spectral density is closely compared with the wall shear-stress dipole source of a turbulent channel flow at $Re_{\tau}=175$. A constant decaying rate of the acoustic power spectrum, $f^{-8/5}$ is found to be related to the turbulent bursts of the correlated longitudinal structures such as hairpin vortex and their merged structures (or hairpin packets). The power spectra of the streamwise velocity fluctuations across the turbulent boundary layer indicate that the most intensive noise at ${\omega}^+$ < 0.1 is produced in the buffer layer with fluctuations of the longitudinal structures ($k_zR$ < 1.5).

A Comparative Study on Tests of Correlation (상관계수에 대한 검정법 비교)

  • Cho, Hyun-Joo;Song, Myung-Unn;Jeong, Dong-Myung;Song, Jae-Kee
    • Journal of the Korean Data and Information Science Society
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    • v.7 no.2
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    • pp.235-245
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    • 1996
  • In this paper, we studied about several methods of testing hypothesis of correlation, specially Approximate method, Empirical method and Bootstrap method. The Approximate method is based on the Fisher's Z-transformation and the Empirical and Bootstrap methods approximate the distribution of the sample correlation coefficient by Monte Carlo simulation and Bootstrap technique, respectively. In order to compare how good these tests are, we computed powers under various alternatives. Consequently, we see that the Approximate test performs very well even if in small sample and all tests have almost the same power in large sample.

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Kinetic Studies of Alkaline Protease from Bacillus licheniformis NCIM-2042

  • Bhunia, Biswanath;Basak, Bikram;Bhattacharya, Pinaki;Dey, Apurba
    • Journal of Microbiology and Biotechnology
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    • v.22 no.12
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    • pp.1758-1766
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    • 2012
  • An extensive investigation was carried out to describe the kinetics of cell growth, substrate consumption, and product formation in the batch fermentation using starch as substrate. Evaluation of intrinsic kinetic parameters was carried out using a best-fit unstructured model. A nonlinear regression technique was applied for computational purpose. The Andrew's model showed a comparatively better $R^2$ value among all tested models. The values of specific growth rate (${\mu}_{max}$), saturation constant ($K_S$), inhibition constant ($K_I$), and $Y_{X/S}$ were found to be 0.109 $h^{-1}$, 11.1 g/l, 0.012 g/l, and 1.003, respectively. The Leudeking-Piret model was used to study the product formation kinetics and the process was found to be growth-associated. The growth-associated constant (${\alpha}$) for protease production was sensitive to substrate concentration. Its value was fairly constant up to a substrate concentration of 30.8 g/l, and then decreased.

Study of the Design of Data Acquisition and Analysis Systems for Multi-purpose Regional Energy Systems

  • Lee, Han-Sang;Yoon, Dong-Hee;Jang, Gil-Soo;Park, Jong-Keun;Park, Goon-Cherl
    • Journal of Electrical Engineering and Technology
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    • v.5 no.1
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    • pp.16-20
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    • 2010
  • Recently, the smart grid has become a hot issue and interest in related power sources have increased accordingly. The implementation of a smart grid can enable many generation resources to be linked to the power system, including small-scale reactors for the purpose of co-generation. Research on small-scale reactors is being carried out all over the world. Similarly, Korea is also conducting research on multi-purpose regional energy systems using nuclear energy. This paper proposes a real-time data acquisition and analysis system for small-scale reactors, and is known as the REX-10 (Regional Energy rX 10 MVA). This analysis requires real-time simulations for the power system since it needs data communication with a remote REX-10. A RTDS (Real Time Digital Simulator) has been used for the simulation, and a SCADA/HMI system interfaced with the RTDS is proposed for the purpose of monitoring and control of the regional energy system.

Improving Hydraulic System Design by Analysis Model of a Self-propelled Spinach Harvester (자주식 시금치 수확장치 해석모델을 활용한 유압시스템 개선 설계 제안)

  • Noh, Dae Kyung;Lee, Dong Won;Lee, Jong Su;Jang, Joo Sup
    • Journal of Drive and Control
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    • v.19 no.1
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    • pp.69-75
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    • 2022
  • This study aimed to develop solutions for the intermittent performance deterioration of self-propelled spinach harvesters through analysis model. The study was conducted in the following manner. First, changes in performance deterioration and surplus flow, which result from oil temperature changes, were analyzed by simulating actual sequential harvesting movements, which involve driving with actuators operated simultaneously, by analysis model developed in a previous study. Second, fundamental solutions for surplus flow problems were presented. Third, the solutions were applied to a virtual environment to present their practicality and quantitative effects. The two solutions based on the study results were as follows. First, a closed center-type directional control valve was applied to the hydraulic circuit. Second, an unloading system was set up through an on-off solenoid valve.

Design for Increasing Displacement Volume of Gerotor Pumps using Virtual Design Environment (가상 설계 환경을 활용한 지로터 펌프의 배제용적 증량 설계 사례)

  • Dae Kyung Noh;Dong Won Lee;Jeong Bae Jeon;Joo Sup Jang
    • Journal of Drive and Control
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    • v.21 no.2
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    • pp.15-22
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    • 2024
  • The objective of this study was to examine whether a gerotor pump used in a transmission could be converted into an electric vehicle thermal management system pump using a virtual design environment. To achieve this objective, we first built an environment that could analyze the performance of a gerotor pump in heat transfer fluid. Flow rate, pressure, and volumetric efficiency were then analyzed when using heat transfer fluid in a gerotor pump. Finally, how large the displacement volume of the pump should be designed when using a heat transfer fluid other than oil was determined. Based on results of this study, it is expected that gerotor pumps will be applied to new business fields such as electric vehicle cooling systems.

VRc Photometry of Dwarf Cepheids

  • Kim, Chulhee-;Michael-D.Joner
    • Bulletin of the Korean Space Science Society
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    • 1993.10a
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    • pp.15-15
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    • 1993
  • Revised Yale Isochrone(Green et al, 1987)과 Lee의 HB simulation data(LEE '||'&'||' Demarque 1990)을 이용하여 Park이 만든 CMD simulation program(Park 1983).에 쌍성을 첨가하면 CMD에 어느 정도의 영향을 나타내게 되는가를 조사하였다. MS, SGB와 RGB는 큰 변화가 없었으나, HB에서는 많은 변화를 나타내었다. 193919 S02401193919 ^x We have observed the emission of HC3N J= 4-3, 5-4 10-9 and 12-11 transitions toward the Sgr B2 central region in an area of 150"XISO" with resolutions of16"-48". The intensities and central velocities of line profiles show significant variations with positions. In contrast to the in tensities of the low J-level transitions which gradually increase from the central source toward the outside region the HC3N emission of the high J-level transition become stronger toward the central radio continuum source MO5. Systematic chainge in the radial velocity of each line profile occurs along north-south direction there are a few peaks in most line profiles, and these indicate that there not multiple velocity components along the line of sight. Distributions of excitation temperah at and column density which were estimated from the excitation calculations show the existence of a small(IxEpc),hot(Tex> SOK) core which contains two tempegatlue peaks at -15" east and north of MDS. The column density of HCaN is (1-3):n1014cm-2. Column density at distant position from MD5 is larger than that in the (:entral region. We have deduced that this hot-core has a mass of 10sR1 which i:s about an order of magnitude larger those obtained by previous studies.previous studies.

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Effect of nonlinear FG-CNT distribution on mechanical properties of functionally graded nano-composite beam

  • Zerrouki, Rachid;Karas, Abdelkader;Zidour, Mohamed;Bousahla, Abdelmoumen Anis;Tounsi, Abdelouahed;Bourada, Fouad;Tounsi, Abdeldjebbar;Benrahou, Kouider Halim;Mahmoud, S.R.
    • Structural Engineering and Mechanics
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    • v.78 no.2
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    • pp.117-124
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    • 2021
  • This work focused on the novel numerical tool for the bending responses of carbon nanotube reinforced composites (CNTRC) beams. The higher order shear deformation beam theory (HSDT) is used to determine strain-displacement relationships. A new exponential function was introduced into the carbon nanotube (CNT) volume fraction equation to show the effect of the CNT distribution on the CNTRC beams through displacements and stresses. To determine the mechanical properties of CNTRCs, the rule of the mixture was employed by assuming that the single-walled carbon nanotubes (SWCNTs)are aligned and distributed in the matrix. The governing equations were derived by Hamilton's principle, and the mathematical models presented in this work are numerically provided to verify the accuracy of the present theory. The effects of aspect ratio (l/d), CNT volume fraction (Vcnt), and the order of exponent (n) on the displacement and stresses are presented and discussed in detail. Based on the analytical results. It turns out that the increase of the exponent degree (n) makes the X-beam stiffer and the exponential CNTs distribution plays an indispensable role to improve the mechanical properties of the CNTRC beams.

Development of an MCNP-Based Cone-Beam CT Simulator (MCNP 기반의 CBCT 전산모사 시스템 개발)

  • Lim, Chang-Hwy;Cho, Min-Kook;Han, Jong-Chul;Youn, Han-Bean;Yun, Seung-Man;Cheong, Min-Ho;Kim, Ho-Kyung
    • Journal of the Korean Society for Nondestructive Testing
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    • v.29 no.4
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    • pp.351-359
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    • 2009
  • We have developed a computer simulator fur cone-beam computed tomography (CBCT) based on the commercial Monte Carlo code, MCNP. All the functions to generate input files, run MCNP, convert output files to image data, reconstruct tomographs were realized in graphical user-interface form. The performance of the simulator was demonstrated by comparing with the experimental data. Although some discrepancies were observed due to the ignorance of the detailed physics in the simulation, such as scattered X-rays and noise in image sensors, the overall tendency was well agreed between the measured and simulated data. The developed simulator will be very useful for understanding the operation and the better design of CT systems.

Bioelectrical Impedance Analysis at Popliteal Regions of Human Body using BIMS

  • Kim, J.H.;Kim, S.S.;Kim, S.H.;Baik, S.W.;Jeon, G.R.
    • Journal of Sensor Science and Technology
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    • v.25 no.1
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    • pp.1-7
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    • 2016
  • Bioelectrical impedance (BI) at popliteal regions was measured using a bioelectrical impedance measurement system (BIMS), which employs the multi-frequency and the two-electrode method. Experiments were performed as follows. First, a constant AC current of $800{\mu}A$ was applied to the popliteal regions (left and right) and the BI was measured at eight different frequencies from 10 to 500 kHz. When the applied frequency greater than 50 kHz was applied to human's popliteal regions, the BI was decreased significantly. Logarithmic plot of impedance vs. frequency indicated two different mechanisms in the impedance phenomena before and after 50 kHz. Second, the relationship between resistance and reactance was obtained with respect to the applied frequency using BI (resistance and reactance) acquired from the popliteal regions. The phase angle (PA) was found to be strongly dependent on frequency. At 50 kHz, the PA at the right popliteal region was $7.8^{\circ}$ slightly larger than $7.6^{\circ}$ at the left popliteal region. Third, BI values of extracellular fluid (ECF) and intracellular fluid (ICF) were calculated using BIMS. At 10 kHz, the BI values of ECF at the left and right popliteal regions were $1664.14{\Omega}$ and $1614.08{\Omega}$, respectively. The BI values of ECF and ICF decreased sharply in the frequency range of 10 to 50 kHz, and gradually decreased up to 500 kHz. Logarithmic plot of BI vs. frequency shows that the BI of ICF decreased noticeably at high frequency above 300 kHz because of a large decrease in the capacitance of the cell membrane.