• 한국수자원학회논문집
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• 제38권10호
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• pp.811-824
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• 2005

ADCP는 음파의 도플러 효과를 이용하여 하천을 횡단하면서 단시간에 유속과 유량을 측정할 수 있는 장비이다. 본 연구는 현장 하천에서 ADCP를 이동식으로 운용하여 측정한 유속, 유량 자료를 동일한 지점에서 측정한 유속-면적법과 비교하여 ADCP를 이용한 유속, 유량 자료의 특성을 살펴볼 목적으로 수행되었다. ADCP에 의해 측정된 수심 분포는 직접 측심에 의해 측정한 수심 분포와 거의 일치하였다. ADCP로 측정한 유속은 순간적이므로 개별 연직유속분포는 시간평균한 유속-면적법 자료와 차이가 있었으나 유속 측선의 좌우에 근접한 자료를 공간적으로 평균할 경우 그 차이는 감소하고 유사한 유속 패턴을 나타내었으며, 왕복하여 반복한 측정 자료를 평균할 경우에도 시간평균한 자료와 비슷한 연직유속분포를 나타내었다. 수평유속분포의 경우 ADCP의 개별 자료 및 이를 중간단면적법에 해당하는 구간 하폭만큼 평균한 자료 역시 유속-면적법 자료와 잘 일치하는 양상을 나타내었다. 유량의 경우 한 지점에서 수 회 이상 평균한 값은 유속-면적법과 비교하여 $0.1\%{\~}9.3\%$의 차이가 나는 것으로 조사되었으며, 반복 측정 횟수를 늘릴 경우 유속-면적법 대비 오차가 감소하는 것으로 나타났다.

• 한국지반공학회논문집
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• 제38권8호
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• pp.17-27
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• 2022

김해평야 퇴적층의 동적 특성을 결정하기 위해 6개의 위치에서 상시미동 수평-수직비(HVSR)법으로 지반 고유진동수(f₀)를 도출하고 High frequency f-k방법과 Modified Spatial Autocorrelation 방법을 적용하여 상시미동 기반 표면파 분석을 수행하였다. 레일리파 분산곡선과 지반 고유진동수를 바탕으로 역해석을 실시하여 전단파 속도 주상도를 도출하였다. 분석 결과에 의하면 김해평야 퇴적층 지역은 1hz 이상의 진동수 대역에서 상당한 규모의 지반운동 증폭이 예상된다. 천부 퇴적층은 대체로 200m/s 내외의 전단파 속도를 보이고 60m~100m 사이의 깊이에서 기반암이 존재할 것으로 추정되며, 다수의 위치에서 천부 퇴적층과 기반암 사이에 V_s=400m/s 가량의 하성 퇴적층이 존재하는 것으로 나타났다. 역해석 결과를 바탕으로 김해평야 퇴적층의 전단파 속도-깊이 모델을 도출하였으며, 본 연구에 따르면 김해평야 퇴적층 지역에서 내진설계일반(KDS 17 10 00)의 S6지반에 해당하는 위치의 면적은 상당할 것으로 예상된다.

• 천문학회보
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• 제46권2호
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• pp.70.1-70.1
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• 2021

We examine the HI gas kinematics and distributions of galaxy pairs in group or cluster environments from high-resolution Australian Square Kilometer Array Pathfinder (ASKAP) WALLABY pilot observations. We use 32 well-resolved close pair galaxies from the Hydra, Norma, and NGC 4636, two clusters and a group of which are identified by their spectroscopy information and additional visual inspection. We perform profile decomposition of HI velocity profiles of the galaxies using a new tool, BAYGAUD which allows us to separate a line-of-sight velocity profile into an optimal number of Gaussian components based on Bayesian MCMC techniques. Then, we construct super profiles via stacking of individual HI velocity profiles after aligning their central velocities. We fit a model which consists of double Gaussian components to the super profiles, and classify them as kinematically cold and warm HI gas components with respect to their velocity dispersions, narrower or wider 𝜎, respectively. The kinematically cold HI gas reservoir (M_cold/M_HI) of the paired galaxies is found to be relatively higher than that of unpaired control samples in the clusters and the group, showing a positive correlation with the HI mass in general. Additionally, we quantify the gravitational instability of the HI gas disk of the sample galaxies using their Toomre Q parameters and HI morphological disturbances. While no significant difference is found for the Q parameter values between the paired and unpaired galaxies, the paired galaxies tend to have larger HI asymmetry values which are derived using their moment0 map compared to those of the non-paired control sample galaxies in the distribution.

• 한국군사과학기술학회지
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• 제14권1호
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• pp.147-153
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• 2011

A series of nonequilibrium molecular dynamics(NEMD) simulations are performed to investigate the kinetic energy and velocity distributions of molecules in shock waves. In the simulations, argon molecules are used as a medium gas through which shock waves are propagating. The kinetic energy distribution profiles reveals that as a strong shock wave whose Mach number is 27.1 is applied, 39.6% of argon molecules inside the shock wave have larger kinetic energy than molecular ionization energy. This indicates that an application of a strong shock wave to argon gas can give rise to an intense light. The velocity distribution profiles in z direction along which shock waves propagate clearly represent two Maxwell-Boltzmann distributions of molecular velocities in two equilibrium regions and one bimodal velocity distribution profile that is attributed to a nonequilibrium region. The peak appearing in the directional temperature in z direction is discussed on a basis of the bimodal velocity distribution in the nonequilibrium region.

• 천문학회지
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• 제30권1호
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• pp.13-25
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• 1997

Sobolev approximation can be adopted to a macroscopic supersonic motion comparatively larger than a random (thermal) one. It has recently been applied not only to the winds of hot early type stars, but also to envelopes of late type giants and/or supergiants. However, since the ratio of wind velocity to stochastic one is comparatively small in the winds of these stars, the condition for applying the Sobolev approximation is not fulfilled any more. Therefore the validity of the Sobolev approximation must be checked. We have calculated exact P Cygni profiles with various velocity ratios, $V_\infty/V_{sto}$, using the accelerated lambda iteration method, comparing with those obtained by the Sobolev approximation. While the velocity ratio decrease, serious deviations have been occured over the whole line profile. When the gradual increase in the velocity structure happens near the surface of star, the amount of deviations become more serious even at the high velocity ratios. The investigations have been applied to observed UV line profile of CIV in the Copernicus spectrums $of\;\zeta\;Puppis\;and\;NV\;of\;\tau\;Sco$. In case of $\tau$ Sco which has an expanding envelope with the gradual velocity increase in the inner region, The Sobolev approximation has given the serious deviations in the line profiles.

• 설비공학논문집
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• 제27권7호
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• pp.344-353
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• 2015

In the present study the characteristics of turbulent oscillatory flows in a square-sectional $180^{\circ}$curved duct were investigated experimentally. A series of experiments for air flow were conducted to measure axial velocity profiles, secondary flow velocity profiles and pressure distributions. The measurements were made by a Laser Doppler Velocimeter (LDV) system with a data acquisition and processing system which includes Rotating Machinery Resolve (RMR) and PHASE software. The results from the experiment are summarized as follows. (1) The maximum velocity moved toward the outer wall from the region of a bend angle of $30^{\circ}$. The velocity distribution had a positive value extended over the total phase in the region of a bend angle of $150^{\circ}$. (2) Secondary flows were generally proportional to the velocity of the main flow. The intensity of the secondary flow was about 25% as much as that in the axial direction. (3) Pressure distributions were effects of the oscillatory Dean number and respective region.

• International Journal of Fluid Machinery and Systems
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• 제2권4호
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• pp.363-374
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• 2009

The 2D flow around 13 similar stay-vane profiles with different trailing edge geometries is investigated to determinate the main characteristics of the excitation forces for each one of them and their respective dynamic behaviors when modeled as a free-oscillating system. The main goal is avoid problems with cracks of hydraulic turbines components. A stay vane profile with a history of cracks was selected as the basis for this work. The commercial finite-volume code $FLUENT^{(R)}$ was employed in the simulations of the stationary profiles and, then, modified to take into account the transversal motion of elastically mounted profiles with equivalent structural stiffness and damping. The k-$\omega$ SST turbulence model is employed in all simulations and a deforming mesh technique used for models with profile motion. The static-model simulations were carried out for each one of the 13 geometries using a constant far field flow velocity value in order to determine the lift force oscillating frequency and amplitude as a function of the geometry. The free-oscillating stay-vane simulations were run with a low mass-damping parameter ($m^*{\xi}=0.0072$) and a single mean flow velocity value (5m/s). The structural bending stiffness of the stay-vane is defined by the Reduced Velocity parameter (Vr). The dynamic analyses were divided into two sets. The first set of simulations was carried out only for one profile with $2{\leq}Vr{\leq}12$. The second set of simulations focused on determining the behavior of each one of the 13 profiles in resonance.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1022-1027
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• 2003

The Motion controllers provide the sophisticated performance and enhanced capabilities we can see in the movements of robotic systems. Several types of motion controllers are available, some based on the kind of overall control system in use. PLC (Programmable Logic Controller)-based motion controllers still predominate. The many peoples use MCU (Micro Controller Unit)-based board level motion controllers and will continue to in the near-term future. These motion controllers control a variety motor system like robotic systems. Generally, They consist of large and complex circuits. PLC-based motion controller consists of high performance PLC, development tool, and application specific software. It can be cause to generate several problems that are large size and space, much cabling, and additional high coasts. MCU-based motion controller consists of memories like ROM and RAM, I/O interface ports, and decoder in order to operate MCU. Additionally, it needs DPRAM to communicate with host PC, counter to get position information of motor by using encoder signal, additional circuits to control servo, and application specific software to generate a various velocity profiles. It can be causes to generate several problems that are overall system complexity, large size and space, much cabling, large power consumption and additional high costs. Also, it needs much times to calculate velocity profile because of generating by software method and don't generate various velocity profiles like arbitrary velocity profile. Therefore, It is hard to generate expected various velocity profiles. And further, to embed real-time OS (Operating System) is considered for more reliable motion control. In this paper, the structure of chip-based precision motion controller is proposed to solve above-mentioned problems of control systems. This proposed motion controller is designed with a FPGA (Field Programmable Gate Arrays) by using the VHDL (Very high speed integrated circuit Hardware Description Language) and Handel-C that is program language for deign hardware. This motion controller consists of Velocity Profile Generator (VPG) part to generate expected various velocity profiles, PCI Interface part to communicate with host PC, Feedback Counter part to get position information by using encoder signal, Clock Generator to generate expected various clock signal, Controller part to control position of motor with generated velocity profile and position information, and Data Converter part to convert and transmit compatible data to D/A converter.

• 한국결정성장학회지
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• 제15권4호
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• pp.129-134
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• 2005

초크랄스키 단결정장치내 실리콘 유동의 자기장효과에 대한 수치해석을 하였다. 8" 단결정 성장과정에서 난류 모형을 사용하여 수송현상을 계산하였다. 도가니 회전수가 작으면 자연대류가 지배적이었다. 도가니 회전수가 증가할수록 강제대류가 증가되며 온도 분포는 더 넓어진다. cusp 자기장을 인가하면 도가니근처의 유동이 크게 감소하며 온도분포는 전도의 경우와 비슷해진다.

• Journal of Astronomy and Space Sciences
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• 제9권1호
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• pp.120-125
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• 1992

쌍성계인 VV Cep에 대해 복사 전달 방정식을 수치적분하여 선 윤곽을 구하였다. Sobolcv 이론을 이용하여 원천함수를 구하고, 초거성의 항성풍의 속도분포는 V(r) = V$\infty(1-R_c/r)^{1/2}$으로 가정하였다. 연속선으로 정규화한 선 윤곽이 공전궤도 위상 0.06에서는 등속도면이 최종속도의 1/2이 되는 곳에서 최대값을 나타냈으며 공전궤도 위상 0.80에서는 속도가 0인 곳에서 나타났다.