• 한국분무공학회지
• /
• 제6권4호
• /
• pp.1-13
• /
• 2001

In the pesticides sprays, spray and atomization technologies to increase the deposition and reduce the drift are briefly reviewed. Further research is needed to deduce a measure of drift risk in sprays with different structures, velocity profiles. For flat fan nozzles, the data of breakup length and thickness of liquid sheet are essential to understand the atomization processes and develop the transport model to target. In the air-assisted spray technology to reduce drift, further works on the effect of application height on drift and air assistance on droplet size should be followed. In addition, methods for quantifying included air in the air inclusion techniques are required. A few researches on the droplet size of fallout can be found in the literature. A combined technology with electrostatic method into one of method for the reduction of drift may be an effective strategy for increasing deposition and reducing drift.

• 대한기계학회논문집B
• /
• 제20권12호
• /
• pp.3960-3969
• /
• 1996

A fluid flow inside a circular cylinder subject to horizontal and circular oscillation is analyzed theoretically. Under the assumption of small-amplitude oscillation, the governing equations take linear forms. The velocity field is obtained in terms of the first kind of Bessel function of order 1. It was found that a particle describes an orbit close to a circle in the central region and an arc near the side wall. We also obtained the Stokes' drift velocity induced by the traveling wave along the circumferential direction. The Eulerian streaming velocities at the edge of the bottom and side boundary layers were also obtained. It was shown that the vertical component of the steady streaming velocity on the side wall is almost proportional to the amplitude of the free surface motion.

• Journal of Advanced Marine Engineering and Technology
• /
• 제23권4호
• /
• pp.559-564
• /
• 1999

A particle image velocimetry is the representative technique for measuring flow velocities at whole field simultaneously. The present study adopted the PTV method for velocity acquisition in a square enclosure with initially isothermal fluid by using a general lamp-based sheet light source. The enclosure was composed of hot and cold vertical wall and was confined by two horizon-tal adiabatic walls. The drift velocities were measured and the drift was visualized by PTV for a rayleigh number of 5.28{\times}10^8.$ Obtained instant simulataneous velocity vectors show flow pattern and the result of horizontal velocity profile agree well with the numerical result.

• 한국농업기계학회:학술대회논문집
• /
• 한국농업기계학회 2000년도 THE THIRD INTERNATIONAL CONFERENCE ON AGRICULTURAL MACHINERY ENGINEERING. V.III
• /
• pp.749-756
• /
• 2000

Chemical application, one of the most important crop management processes happened to cause spray drift, that would threaten farmers in field as well as dwellers in rural region. Spray drift was affected by micro-meteorological parameters. In Korea, a boom sprayer was introduced but good effects of a boom sprayer was not evaluated. A study to evaluate short distance drift characteristics of a boom sprayer in paddy fields has been undergoing and determining wind characteristics in paddy field was the main purpose of this paper. Micro-meteorological information has been pre-requisite information for evaluating drift in both long and short distances or in both theoretical and experimental ways. Wind velocity, Reynolds stresses, turbulence intensity, skewness, kurtosis etc. were evaluated with height from the ground using a 2-dimensional probe and a hot wire anemometer system.

• International Journal of Aeronautical and Space Sciences
• /
• 제15권3호
• /
• pp.293-301
• /
• 2014

We present a study of vertical dynamics control of an electrostatically levitated gyro-accelerometer considering the wobbling effect and propose a tilt stabilization method with newly introduced control electrodes. Typically, a rotor in a vacuum rotates at high velocity, which may create a drift rate and lead to displacement instability due to the tilt angle of the rotor. To analyze this, first we set up a vertical dynamic equation and determined simulation results regarding displacement control. After deriving an equation for drift dynamics, we analyzed the drift rate of the rotor and the wobbling effect for displacement control quantitatively. Then, we designed new sub-electrodes for moment control that will decrease the drift amplitude of wobbling dynamics. Finally, a simulation study demonstrated that the vertical displacement control with the wobbling compensation electrodes mitigated the rotor's drift rate, showing the effectiveness of the newly proposed control electrodes.

• Journal of Advanced Marine Engineering and Technology
• /
• 제27권7호
• /
• pp.914-920
• /
• 2003

In this paper, we deal with two drift compensation algorithms of acceleration sensor for measuring the galloping on power transmission line. Firstly, the block diagram of galloping measurement system is given and a galloping model is presented. Secondly, two compensation algorithms, a simple compensation and a period compensation, are proposed. A simple compensation algorithm uses the drifts of velocity and distance at fixed periods, so it is useful for constant drift case. Next, a period compensation algorithm can compensate a periodic drift. This algorithm uses the previous measured data and compensated data for constant period, where the period is obtained by FFT method. Lastly, the effectiveness of proposed algorithms is verified by comparing between two algorithms in simulation, and its characteristics and the drift error bound are shown, respectively.

• 전기학회논문지P
• /
• 제60권3호
• /
• pp.105-109
• /
• 2011

Drift Velocity of Electrons in pure $CF_4$, $CH_4$ and mixtures of $CF_4$ and Ar. Have been analyzed over a range of the reduced electric field strength between 0.1 and 350[Td] by the two-term approximation of the Boltzmann equation (BEq.) method and the Monte Carlo simulation (MCS). The results of the Boltzmann equation and the Monte Carlo simulation have been compared with the data presented by several workers. The deduced transport coefficients for electrons agree reasonably well with the experimental and simulation data obtained by Nakamura and Hayashi. The energy distribution function of electrons in $CF_4$-Ar mixtures shows the Maxwellian distribution for energy. That is, f(${\varepsilon}$) has the symmetrical shape whose axis of symmetry is a most probably energy. The measured results and the calculated results have been compared each other.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2001년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 연구회
• /
• pp.29-32
• /
• 2001

We measured the electron transport coefficients(the electron drift velocity, W, and the longitudinal diffusion coefficient, $D_L$) in pure $CF_4$ over the E/N range from 0.04 Td to 250 Td by the double shutter drift tube. And these electron transport coefficients in pure $CF_4$ were calculated over the E/N range from 0.01 to 250 Td at 1 Torr by using the two-term approximation of the Boltzmann equation.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2000년도 하계학술대회 논문집
• /
• pp.934-941
• /
• 2000

We measured the electron transport coefficients, the electron drift velocity W and the longitudinal diffusion coefficient $D_{L}$ in the 0.526% and 5.05% $C_{3}F_{8}$-Ar mixtures over the E/N range from 0.01 Td to 100 Td by the double shutter drift tube, and compared the measured results by Hunter et al. with those. We determined the inelastic collision cross sections for the $C_{3}F_{8}$ molecule by the comparison of the present measurements and the calculation of electron transport coefficients in the $C_{3}F_{8}$-Ar mixtures by using a multi-term Boltzmann equation analysis.

• 한국해안해양공학회지
• /
• 제7권4호
• /
• pp.329-339
• /
• 1995

파 운동에 의한 수표면 부유속도를 규명하기 위하여 Stokes 2차 파이론, Stokes 5차 파이론 및 Longuet-Higgins(1953)의 전도해 등에 의한 이론치를 2차원 조파수조에서 실측한 실험치와 비교분석하였다. 실험간 상대수심의 범위는 0.04