• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.8
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• pp.2062-2072
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• 1994

This paper presents the development of a fuzzy controller for driving camera pan/tilt device so that the camera's viewing direction can automatically track a moving object. To achieve computational efficiency a non-contact type displacement follower is used as a feedback sensor instead of a vision camera. The displacement follower, however, is extremely sensitive to object's lighting condition and results in unstable response at high speed. To this end, a fuzzy controller is developed in such a way to provide stable tracking performance at high speed where the sensory signal is subjected to intermittant disturbances of large magnitude. The test result shows stable tracking response even for high speed and non-uniform lighting condition. The resulting camera autotracking system can be adopted as an effective tool for visual transfer in the context of teleoperation and autonomous robotics.

• Journal of Environmental Science International
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• v.3 no.1
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• pp.31-38
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• 1994

The diffusion of the pollutants released into atmosphere is dependent on its chemical reaction, topography and micrometeorological characteristics. The purpose of the study is to investigate how much micrometeorological characteristics such as stability, wind speed and mixing height affect the diffusion of the air pollutants. For this purpose, this paper let 1) the basic theory be K-theory, 2) eddy diffusivity and wind speed be dependent on mixing height and stability, and 3) Grout method be used for numeric calculation. The result was 1) the more unstable condition, the higher mixing height and the higher wind speed we, the lower pollutants concentration appears, 2) the most intensive effect on the distribution of the pollutant concentration is the atmospheric stability.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.5
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• pp.191-197
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• 2007

Inclined surface milling in the mould and die industries is one of the most commonly needed cutting process. For the variety and complexity of cutting characteristics in various cutting condition, it is difficult to select a optimal tool path orientation. Especially, when the cutting process becomes unstable, it induces self-exited vibrations, a frequent cause of poor tool life, rough surface finish, damage to the workpiece and the machine tool itself, and excessive down time. The comparative results through FFT analysis in this study provide a guideline for the selection tool path orientation.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.206-209
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• 2011

During landing approach, an airplane could experience dynamic unstable motion by the combination of a gust and elevator control to cancel the disturbances. This situation is dangerous and could lead to a loss of an airplane. In this paper, numerical analysis was used to study the effect of pitch oscillating 2-D high lift devices in a landing condition. Experimental data on a pitching naca0012 airfoil was used for code validation. Dynamic characteristics of an airfoil, single slotted flap for mid-class passenger aircraft were analyzed. Unsteady Navier-Stokes analysis was performed with Spalart-Allmaras turbulence model for separation dominant low speed flow. As a result, flow hysteresis of a flapped airfoil was more complex than that of an oscillating airfoil. So, dynamic analysis of a flap in a landing condition is very important for operational safety.

• Tribology and Lubricants
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• v.18 no.1
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• pp.55-60
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• 2002

In many dynamic systems, there are unwanted oscillation which may arise the reduction of performance. Especially in low sliding speed condition, the stick-slip is an important issue because it because unstable motion as well as inaccurate position control in the system. Most previous works on the stick-slip are, however, only concerned with simple modeling under the condition of constant normal force. The normal force and the amount of hydraulic oil are variable with a cylinder stroke in the telescopic boom. This paper presents the pressure variations during stick-slip with the cylinder of telescope boom. Pressure variations by stick-slip has a similar pattern to that of single mass-spring model. The stick-slip is gradually decreased by means of increased flow rate.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1151-1152
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• 2006

In this paper, we examined 10 domestic samples of three different model using thermal, humidity freeze, thermal-endurance and damp heat test under IEC61215 photovoltaic module environmental endurance test condition. Three was almost no changes on power generation. Insulation resistance capacity was much higher than judgement standard but, showed unstable results depending on environmental test items. On external appearance test, there were two models which showed bubble, humidity penetration, seal melted frame phenomenon. From this results, the degree of aging under the external environment is a main cause that shortens photovoltaic module life time. So it is considered that the efforts for finding optimum condition of manufacturing process should be needed.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.541-548
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• 2002

Membrane, cable structure and membrane-cable structural system are more lighter than another common structural system, and these are able to be effectively build Lip spatial structures using axial stiffness. However when the load reach at critical load level, it might be happened snap-through or bifurcation according to the structure's shape, and these collapse mechanism should be very important in the design of structures. So, In this paper we study static instability of Zetlin-type cable dome, one of the hybrid cable dome. Moreover, as the unstable behavior of shell structures are very sensitive to the initial condition, we seek to find the effect of initial condition.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.6
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• pp.873-879
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• 2009

The steady breakers at an infant stage are investigated through the numerical simulation. The appearing condition and characteristics of the sub-breaking waves are reviewed by analysing bow waves. The instability analysis is possibly done through the relationship between the free-surface curvature and circumferential force, which is obtained from the momentum equations. Navier-Stokes equations are solved by a finite difference method where the body-fitted coordinate system, the wall function and the advanced mesh system are invoked. The numerical result shows that the gradient of M/$U_s$ is greatly influenced by the Froude number and the decrease of M/$U_s$ indicates that the flows are unstable. Additionally flows with plunging or spilling are simulated successfully, but the application of breakers to the severely broken wave still remains to be settled in the future.

• Korean Journal of Organic Agriculture
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• v.25 no.1
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• pp.1-22
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• 2017

The purpose of this research is to analysis actual condition of promoting complex industrialization and changes after promoting, and then to classify organic farmer using cluster analysis based on delineated organic farmer's changes factors. This study also aims to investigate differences in socioeconomic characteristics and behavioral intentions among classified groups of organic farmer's changes. Data were obtained by questionnaire. From the factor analysis, four factors were derived as "Economics", "Public benefit", "Environment and philosophical values" and "Establishing management and the regional bedrock". From the cluster analysis, three cluster were derived as "group that has a positive awareness of promoting complex industry", "group that has a negative awareness of promoting complex industry" and "unstable management and a regional base". And the three classifications were significantly different in the satisfaction and behavioral intentions.

• Progress in Superconductivity and Cryogenics
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• v.21 no.3
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• pp.1-5
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• 2019

The superconductor stability theories are consistently described by the integral formula. If the defined stability function is a simple decreasing function, it becomes a cryogenic stability condition. If the stability function has a maximum value and a minimum value, and the maximum value is less than 0, then it is a cold-end recovery condition. If the maximum value is more than 0, it can be shown that the unstable equilibrium temperature, that is, the MPZ (minimum propagation zone) temperature distribution can exist. The MPZ region is divided into two regions according to the current ratio. At the low current ratio, the maximum dimensionless temperature is greater than 1, and at the relatively high current ratio, the maximum dimensionless temperature is less than 1. In order to predict the minimum quench energy, the dimensionless energy was obtained for the MPZ temperature distribution. In particular, it was shown that the dimensionless energy can be obtained even when the MPZ maximum temperature is 1 or more.