• Annals of Clinical Neurophysiology
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• 제1권2호
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• pp.173-181
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• 1999

Eye movements serve vision by placing the image of an object on the fovea of each retina, and by preventing slippage of images on the retina. The brain employs two modes of ocular motor control, fast eye movements (saccades) and smooth eye movements. Saccades bring the fovea to a target, and smooth eye movements prevent retinal image slip. Smooth eye movements comprise smooth pursuit, the optokinetic reflex, the vestibulo-ocular reflex (VOR), vergence, and fixation. Saccades achieve rapid refixation of targets that fall on the extrafoveal retina by moving the eyes at peak velocities that can exceed $700^{\circ}/s$. Various brain lesions can affect saccadic latency, velocity, or accuracy. Smooth pursuit maintains fixation of a slowly moving target. The pursuit system responds to slippage of an image near the fovea in order to accelerate the eyes to a velocity that matches that of the target. When smooth eye movements velocity fails to match target velocity, catch-up saccades are used to compensate for limited smooth pursuit velocities. The VOR subserves vision by generating conjugate eye movements that are equal and opposite to head movements. If the VOR gain (the ratio of eye velocity to head velocity) is too high or too low, the target image is off the fovea, and head motion causes oscillopsia, an illusory to-and-fro movement of the environment.

• 한국정밀공학회지
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• 제32권10호
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• pp.885-890
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• 2015

Walking on split-belt treadmill has been applied to study walking disabilities, such as osteoarthritis (OA), to show asymmetric walking characteristics. In this study, we compared asymmetric walking in OA patients with healthy subjects under split-belt conditions and examined the reproduction of walking asymmetry in OA. Seven OA patients were instructed to walk at four frequencies, while four healthy subjects walked on a treadmill with tied-belt and split-belt conditions. To compare walking asymmetries, kinetic and kinematic measurements were made using force-plates and motion capture cameras, and subsequently center of mass (CoM) velocity, mechanical work and potential energy were calculated. Horizontal velocity change during split-belt walking of healthy subjects was similar to OA patients. Difference of mechanical work during single support phase occurred due to fall of CoM in fast belt. OA walking asymmetry could be reproduced by reducing differences of belt speeds to prevent rapid fall of CoM.

• 대기
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• 제26권3호
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• pp.435-444
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• 2016

In spite of considerable progress in the recent decades, there still remain large uncertainties in numerical cloud models. In this study, effects of uncertainty in terminal velocity of graupel on cloud simulation are investigated. For this, a two-dimensional bin microphysics cloud model is employed, and deep convective clouds are simulated under idealized environmental conditions. In the sensitivity experiments, the terminal velocity of graupel is changed to twice and half the velocity in the control experiment. In the experiment with fast graupel terminal velocity, a large amount of graupel mass is present in the lower layer. On the other hand, in the experiment with slow graupel terminal velocity, almost all graupel mass remains in the upper layer. The graupel size distribution exhibits that as graupel terminal velocity increases, in the lower layer, the number of graupel particles increases and the peak radius in the graupel mass size distribution decreases. In the experiment with fast graupel terminal velocity, the vertical velocity is decreased mainly due to a decrease in riming that leads to a decrease in latent heat release and an increase in evaporative cooling via evaporation, sublimation, and melting that leads to more stable atmosphere. This decrease in vertical velocity causes graupel particles to fall toward the ground easier. By the changes in graupel terminal velocity, the accumulated surface precipitation amount differs up to about two times. This study reveals that the terminal velocity of graupel should be estimated more accurately than it is now.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2001년도 학술발표회 발표논문집
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• pp.435-440
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• 2001

The purpose of this study was to evaluate mesh size and water velocity for the growth of filamentous periphytic algae(FPA). The growth experiment was carried out in the constructed pilot waterway system with nutrient-rich treated wastewater. Growth rate of FPA was highest at water velocity about 10 cm/s. The maximum standing crop of FPA was $253\;{\mu}g\;chl.a/cm^{3}$, and an average of the net productivity was $3.92\;mgDW/cm^{2}/day\;or\;25.3\;{\mu}g\;chl.a/cm^{2}/day$. Biomass development and growth rates of FPA were highest at the net with 20mm mesh size during the fall season and 10mm mesh size during the winter season.

• Journal of Advanced Marine Engineering and Technology
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• 제23권5호
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• pp.662-670
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• 1999

A numerical prediction was performed to clarify the air motion in the cylinder of an axisymmet-ric four-stroke reciprocating engine at its intake and compression stage. A scheme of finite volume method is used for the calculation. Modified $k-{\varepsilon}$ turbulence model is adopted and wall function is applied to the grids near the wall. The predicted mean velocity and rms velocity profiles showed a reasonable agreement with an available experimental data at its intake and compression stage. The predicted in-cylinder flow fields show that a strong turbulent twin vortex structure is pro-duced during induction but it commences to decay rapidly around inlet valve closure. The mean velocity continues to fall to a low level during compression but the turbulence intensity attains an approximate constant level.

• 센서학회지
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• 제22권1호
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• pp.54-64
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• 2013

In this study, we developed a falling recognition system to transmit SMS data through CDMA communication using a three axises acceleration sensor and a two axises gyro sensor. 5 healthy men were selected into a control group, and the fall recognition system using the three axises acceleration sensor and the two axises gyro sensor was devised to conduct an experiment. The system was attached to the upper of their sternum. According to the experiment protocol, the experiment was carried out 3 times repeatedly divided into 3 specific protocols: falling during gait, falling in stopped state, and falling in everyday life. Data obtained in the falling recognition system and LabVIEW 8.5 were used to decide if falling corresponds to that regulated in an analysis program applying an algorithm proposed in this study. In addition, results from falling recognition were transmitted to designated cellular phone in a SMS (Shot Message Service) form. These research results show that an erroneous detection rate of falling reached 19% in applying an acceleration signal only; 6% in applying an angular velocity; and 2% in applying a proposed algorithm. Such finding suggests that an erroneous detection rate of falling is improved when the proposed algorithm is applied incorporated with acceleration and angular velocity. In this study therefore, we proposed that a falling recognition system implemented in this study can make a contribution to the recognition of falling of the aged or the disabled.

• 한국컴퓨터정보학회논문지
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• 제17권10호
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• pp.55-60
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• 2012

자유 낙하하는 물체가 받는 힘은 중력뿐이다. 우리는 중력만을 받아서 운동하는 것을 자유 낙하 운동이라고 하고 자유 낙하하는 물체를 자유낙체라 한다. 즉, 자유낙체란 물체의 초기 운동 상태와 무관하게 중력의 영향으로만 자유롭게 낙하하는 물체를 말하는 것이다. 본 논문에서는 공기의 저항을 무시하고, 수직방향으로 짧은 거리의 범위내에서 고도에 의한 자유낙하 가속도의 변화가 없다는 가정을 한다. 이러한 가정 하에서 자동차가 수직 상 방향으로 도약하여 최고점에 도달하는 시간, 최대높이, 자동차가 출발 위치로 돌아오는 시간과 자동차의 속도, 자동차가 땅에 떨어질 때의 시간 및 속도에 대해 알 수 있다. 이는 텔레매틱스에서 자동차나 오토바이가 도약하는 정도와 사고의 위험을 측정할 수 있다.

• Journal of information and communication convergence engineering
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• 제10권2호
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• pp.181-186
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• 2012

Telematics services include automatic location tracking for emergency rescue, which is available for use in case of a car accident due to falling off roadways. This paper presents a simulation study on how far a car will fall before it hits the ground if it drops off of a roadway due to an accident or a natural disaster. The greatest horizontal distance the falling car can travel is presented in this paper, based on the assumption that air resistance as well as the direction and degree of acceleration due to gravity is negligible. This paper also presents the depth of the dent caused by the car sinking into the ground, the time it took for the car to fall free, and the velocity at which it travelled and horizontal distance it traveled. In this paper, the damage done to cars that crash into the ground and the dangers thereof are graphically represented.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2002년도 추계학술발표논문집
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• pp.253-257
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• 2002

본 논문에서는 아이스크림용 아이스 콘에서 콘 부분을 만들기 위한 금형의 제작시 필요한 구조적 안정성을 평가할 수 있는 유동해석을 수행하였다. 유동해석을 수행하기 위하여 상용 유한요소해석 코드인 ANSYS클 활용하였으며 내압조건, 경계조건, 구속조건 등을 고려하여 아이스 콘 금형내부의 유동 흐름을 압력조건의 변화에 따라 구하였다.

• 천문학논총
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• 제17권1호
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• pp.11-14
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• 2002

Our examination of the relations of spherically symmetric accretion on a massive point object to viscous drag, neglecting gas pressure and using self-similar transformation, shows the behaviors of the asymptotic solutions? in the regions near to and far from the center. The viscosity reduces the free-fall velocity by the factor $(1\;+\;\zeta) ^{-1}$, and causes flattening in the density distribution. Therefore, the viscosity leads to the reduction of the mass accretion rate.