• Composites Research
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• v.35 no.4
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• pp.277-282
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• 2022

In this study, a smart material applicable to speed bumps was developed using low-cost starch and waterbased suspensions, and their properties were investigated. Viscosity and shear stress according to the shear rate was measured by a rheometer to observe shear thickening behavior according to starch concentration. The shear thickening phenomenon and applicability to speed bumps were identified macroscopically via drop weight test and bike driving test, measuring the vibration after impact with a driving speed of 5-25 km/h. As a result of the viscosity measurement, shear thickening occurred after the shear thinning region at the beginning, and the critical strain causing the shear thickening phenomenon decreased as the concentration of starch increased. Also, the viscosity and shear stress increased significantly with the increase of the starch concentration. As a result of the drop weight test and the bike driving test, the suspension was changed to a solid-like state in a short time, and the impact energy was absorbed in the fluid. The shear thickening phenomenon easily occurred as the concentration of the fluid and the applied impact (velocity) increased. Therefore, it can be proposed the development of a smart speed bump material that operates in the range of 5-25 km/h with a Non-Newtonian fluid based on water and starch.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.656-660
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• 2009

Various dynamic models of seated posture human body have been developed because the importance about the ride comfort assessment of vehicles is highly emphasized from day to day. The dynamic models of human body make possible the simulation of ride comfort assessment by applied to the vehicle dynamic model. Recently, the importance of ride comfort is also regarded to working vehicles such as excavators and the research of the ride comfort assessment for working vehicle is required. Only vertical vibration dominantly occurs on the seat of the private car driving with constant velocity. In contrast, vertical/fore-and-aft/pitch vibration seriously occurs on the seat of the working excavator. So, the dynamic models of seated human body applied to working vehicles should describe the dynamic characteristics for vertical/fore-and-aft/pitch direction. In this paper, the dynamic characteristics of seated human body are represented as apparent inertia matrix. The apparent inertia matrix is obtained by the vertical/fore-and-aft/pitch excitation of seated human body. 6 resonance frequencies are observed in apparent inertia matrix. This result can be applied to develop the dynamic model for seated posture human body.

• Journal of Positioning, Navigation, and Timing
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• v.4 no.3
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• pp.141-150
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• 2015

In this study, a Global Navigation Satellite System (GNSS) / Inertial Navigation System (INS) / odometer / barometer integrated navigation system that uses a commercial navigation device including Micro Electro Mechanical Systems (MEMS) accelerometer and gyroscope in addition to GNSS, odometer information obtained from a vehicle, and a separate MEMS barometer sensor was implemented, and the performance was verified. In the case of GNSS and GNSS/INS integrated navigation system that are generally used in a navigation device, the performance would deteriorate in areas where GNSS signals are not available. Therefore, an integrated navigation system that calculates a better navigation solution in areas where GNSS signals are not available compared to general GNSS/INS by correcting the velocity error of GNSS/INS using an odometer and by correcting the cumulative altitude error of GNSS/INS using a barometer was suggested. To verify the performance of the navigation system, a commercial navigation device (Softman, Hyundai Mnsoft, http://www.hyundai-mnsoft.com) and a barometer sensor (ST Company) were installed at a vehicle, and an actual driving test was performed. To examine the performance of the algorithm, the navigation solutions of general GNSS/INS and the GNSS/INS/odometer/barometer integrated navigation system were compared in an area where GNSS signals are not available. As a result, a navigation solution that has a smaller position error than that of GNSS/INS could be obtained in the area where GNSS signals are not available.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.7
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• pp.649-657
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• 2004

A windshield wiper system plays a key part in assurance of driver's safety at rainfall. However, because quantity of rain and snow vary irregularly according to time and velocity of automotive, a driver changes speed and operation period of a wiper from time to time in order to secure enough visual field in the traditional windshield wiper system. Because a manual operation of wiper distracts driver's sensitivity and causes inadvertent driving, this is becoming direct cause of traffic accident. Therefore, this paper presents the basic architecture of vision-based smart wiper system and the rain sensing algorithm that regulate speed and interval of wiper automatically according to quantity of rain or snow. Also, this paper introduces the fuzzy wiper control algorithm based on human's expertise, and evaluates performance of suggested algorithm in the simulator model. Especially the vision sensor can measure wider area relatively than the optical rain sensor, hence, this grasps rainfall state more exactly in case disturbance occurs.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.6
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• pp.225-231
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• 2008

For an aspect ratio (transport length-to-width) of 5, Pr=1.13, Le=1.91, Pe=4.3, Cv=1.01, $P_B=20\;Torr$, the effects of addition of inert gas Ne on thermally buoyancy-driven convection ($Gr=2.44{\times}10^3$) are numerically investigated for further understanding and insight into essence of transport phenomena in two dimensional horizontal enclosures. For $10K{\leq}{\Delta}T{\leq}50\;K$, the crystal growth rate increases from 10 K up to 20 K, and then is slowly decreased until ${\Delat}T=50\;K$, which is likely to be due to the effects of thermo-physical properties stronger than the temperature gradient corresponding to driving force for thermal convection. The dimensional maximum velocity gratitude reflecting the intensity of thermal convection is directly and linearly proportional to the temperature difference between the source and crystal regions. The rate is first order-exponentially decreased for $2{\leq}Ar{\leq}5$. This is related to the finding that the effects of side walls tend to stabilize convection in the growth reactor. In addition, the rate is first order exponentially decayed for $10{\leq}P_B{\leq}200\;Torr$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.3
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• pp.117-124
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• 2010

For Ar=5, Pr=1.18, Le=0.15, Pe=2.89, Cv=1.06, $P_B$=20 Torr, the effects of impurity $(N_2)$ on thermally and solutally buoyancy-driven convection ($Gr_t=3.46{\times}10^4$ and $Gr_s=6.02{\times}10^5$, respectively) are theoretically investigated for further understanding and insight into an essence of thermo-solutal convection occurring in the vapor phase during the physical vapor transport. For $10K{\leq}{\Delta}T{\leq}50K$, the crystal growth rates are intimately related and linearly proportional to a temperature difference between the source and crystal region which is a driving force for thermally buoyancy-driven convection. Moreover, both the dimensionless Peclet number (Pe) and dimensional maximum velocity magnitudes are directly and linearly proportional to ${\Delta}T$. The growth rate is second order-exponentially decayed for $2{\leq}Ar{\leq}5$. This is related to a finding that the effects of side walls tend to stabilize the thermo-solutal convection in the growth reactor. Finally, the growth rate is found to be first order exponentially decayed for $10{\leq}P_B{\leq}200$ Torr.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.2
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• pp.251-259
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• 2000

The ionic wind formed in a nonuniform electric field has been recognized to have a significant effect on particle collection in an electrostatic precipitator(ESP). Under normal operating conditions the effect of ionic wind is not pronounced. However, as the flow velocity becomes smaller, the ionic wind becomes pronounced and induces secondary flow, which has a significant influence on the flow field and the particle collecting efficiency. In this paper, experiments for investigating the effect of secondary flow on collection efficiencies were carried out by changing the flow velocities in 0.2-0.7m/s and the applied voltages in 9-11kV/cm. The particle size distributions and concentrations are measured by DMA and CNC. To analyze the experimental results, numerical analysis of electric filed in ESP was carried out. It shows that particle collection is influenced by two independent dimensionless numbers, $Re_{ehd}\;and\;Re_{flow}$ not by $N_{ehd}$ alone. When $Re_{flow}$, decreases for constant $Re_{ehd}$, the secondary flow prohibits the particle collection. But when $Re_{ehd}$ increases for constant $Re_{flow}$, it enhances the particle collection by driving the particles into the collection region.

• Journal of the Korean Society for Railway
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• v.11 no.2
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• pp.203-210
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• 2008

Since hub wheel BLDC Motor consisted of wheel and BLDCM (Brushless DC Motor) without gear reducer has high efficiency and low operation noise, it can be utilized to a driving wheel at some light rail systems. However, installing sensors for speedometer on a Hub-Wheel motor is not easy, so it requires a different speed control mechanism method for speed measurement. This paper introduces a speed control method based on simple mathematical model which uses discrete Kalman Filter to estimate and control the speed of the motor.

• Journal of ILASS-Korea
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• v.1 no.2
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• pp.16-23
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• 1996

In case of a high-speed D.I. diesel engine. the injected fuel spray is unavoidable that the impinging on the wall of piston cavity and in this case the geometry of piston cavity has a great influence on the atomization structure and air flow fields. In the field of combustion and in many other spray applications, there are clear evidence of correlation between spray structure and emission of pollutants. Ordinary, the combustion chamber of driving engine have unsteady turbulent flow be attendant on such as the change of temperature, velocity and pressure. So the analysis of spray behavior is difficult. In this study, a single spray was impinged on each cavity wall at indicated angle in a quiescent atmosphere at room temperature and pressure, as being the simplest case, and 3 types of piston cavity such as Dish, Toroidal and Re-entrant type was tested for analyzing the influence of cavity geometry. And hot wire probe was used for analyze non-steady flow characteristics of impinging spray, and to investigate the behavior of spray, the aspects of concentration c(t), standard deviation $\sigma(t)$ and variation factor (v.f.) was measured with the lapse of time.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.6
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• pp.120-127
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• 2007

This paper describes the development of a nonlinear observer for four wheel steer (4WS) vehicle. An observer is designed to estimate the vehicle variables difficult to measure directly. A brake yaw motion controller (BYMC), which uses a PID control method, is also proposed for controlling the brake pressure of the rear and inner wheels to enhance lateral stability. It induces the yaw rate to track the reference yaw rate, and it reduces a slip angle on a slippery road. The braking and steering performances of the anti-lock brake system (ABS) and BYMC are evaluated for various driving conditions, including straight, J-turn, and sinusoidal maneuvers. The simulation results show that developed ABS reduces the stopping distance and increases the longitudinal stability. The observer estimates velocity, slip angle, and yaw rate of 4WS vehicle very well. The results also reveal that the BYMC improves vehicle lateral stability and controllability when various steering inputs are applied.