• Environmental and Resource Economics Review
• /
• v.22 no.2
• /
• pp.393-410
• /
• 2013

We employ a threshold vector error correction models (TVECM) to investigate the nonlinear dynamic adjustment of gasoline prices in Korea. We consider 10 regional gasoline markets including Seoul, Busan, Daegu, Incheon, Kwangju, Daejeon, Ulsan, Kangwon, Chungbuk, Jeonbuk and construct 9 price differences against Seoul. We use the bootstrap procedure suggested by Hansen (1999) and generalized by Lo and Zivot (2001) to show that three-regime TVECM is suitable for our analysis. Results indicate the gasoline price adjustment processes are nonlinear. Our estimation shows that Seoul-Daejeon, Seoul-Daegu and Seoul-Ulsan have bigger transaction costs than other market pairs and thus gasoline prices of these three regional markets are lower than that of Seoul. Gasoline prices of the other 6 regional markets are close to Seoul's price. One interesting finding is that the transaction costs are not proportional to geographical distances. This implies that transportation costs are not the main factor of the transaction costs. The transaction costs may depends on the competition intensity of gasoline markets in supply side.

• Journal of Institute of Control, Robotics and Systems
• /
• v.12 no.4
• /
• pp.358-363
• /
• 2006

This paper demonstrates a new non-contact electronic joystick using single hall sensor which detects a horizontal vector of the magnetic field. Furthermore, in this paper, it is mathematically modeled that nonlinear characteristics between the output of hall sensor and the movement of joystick bar. The dynamic horizontal vector of magnetic flux is detected by the hall sensor while a permanent magnet is rotated with the joystick bar, which has two dimension detecting area. Using the nonlinear adjustment equations, the output signals of hall sensor have been linearized to give higher accuracy in the two dimension movement. Finally, through the real experiments, it is showed that the single hall sensor structure mechanism is superior to the dual sensor structure in sensing the two-dimensional motion without offset.

• Journal of Power Electronics
• /
• v.16 no.6
• /
• pp.2150-2161
• /
• 2016

Mechanical and electrical parameter uncertainties cause dynamic and static estimation errors of the rotor speed and position, resulting in performance deterioration of sensorless control systems. This paper applies an extended nonlinear observer to interior permanent magnet synchronous motors (IPMSM) for the simultaneous estimation of the rotor speed and position. Two compensation methods are proposed to improve the observer performance against parameter uncertainties: an on-line rotational inertia adjustment approach that employs the gradient descent algorithm to suppress dynamic estimation errors, and an equivalent flux error compensation approach to eliminate static estimation errors caused by inaccurate electrical parameters. The effectiveness of the proposed control strategy is demonstrated by experimental tests.

• Smart Structures and Systems
• /
• v.16 no.1
• /
• pp.27-46
• /
• 2015

Active surface adjustment of cable net structures is becoming significant when large-size cable net structures are widely applied in various fields, especially in satellite antennas. A general-duty adjustment method based on active cables is proposed to achieve active surface adjustment or surface profile reconfiguration of cable net structures. Piezoelectric actuators and voice coil actuators are selected for constructing active cable structures and their simplified mechanical models are proposed. A bilevel optimization model of active surface adjustment is proposed based on the nonlinear static model established by the direct stiffness method. A pattern search algorithm combined with the trust region method is developed to solve this optimization problem. Numerical examples of a parabolic cable net reflector are analyzed and different distribution types of active cables are compared.

• Journal of applied mathematics & informatics
• /
• v.26 no.3_4
• /
• pp.739-750
• /
• 2008

A phenomenon which is seen in some of the manufacturing systems and production planning is chaos and the butterfly effect. The butterfly effect points out that in case of the presence of nonlinear relations in system and incorrect estimation of initial values of variables, the error in the estimates of system state will be intensified, and after a while there will be a large distance between available state of system and reality. Using mathematical means and computer simulation, we have tried to demonstrate that in a production system the numerical combination of Cycle Time (CT), Adjustment Time between existing and desired Work In Progress (WIP), and Adjustment Time between current and desired inventory can lead to chaos and butterfly effect in the behavior of the inventory state variable. Our paper concludes with a discussion of a hypothesis that emerged from this research.

• Journal of the Optical Society of Korea
• /
• v.14 no.4
• /
• pp.357-362
• /
• 2010

The joint transform correlator (JTC) has been the best known technique for pattern recognition and identification. This paper proposes a new technique of fringe adjustment by adopting a sinusoidal amplitude-modulated iterative filter convolved with an interference fringe pattern in the joint power spectrum (JPS) domain. The comparison of our new technique and other techniques is presented to show that the newly proposed technique can successfully improve both the correlation peaks and the peak signal-to-noise ratio (PSNR). Simulated results of enhanced interference fringes are also presented.

• Structural Engineering and Mechanics
• /
• v.83 no.2
• /
• pp.135-151
• /
• 2022

The generalized displacement method is a nonlinear solution scheme that follows the equilibrium path of the structure based on the development of the generalized displacement. This method traces the path uniformly with a constant amount of generalized displacement. In this article, we first develop higher-order generalized displacement methods based on multi-point techniques. According to the concept of generalized stiffness, a relation is proposed to adjust the generalized displacement during the path-following. This formulation provides the possibility to change the amount of generalized displacement along the path due to changes in generalized stiffness. We, then, introduce higher-order algorithms of variable generalized displacement method using multi-point methods. Finally, we demonstrate with numerical examples that the presented algorithms, including multi-point generalized displacement methods and multi-point variable generalized displacement methods, are capable of following the equilibrium path. A comparison with the arc length method, generalized displacement method, and multi-point arc-length methods illustrates that the adjustment of generalized displacement significantly reduces the number of steps during the path-following. We also demonstrate that the application of multi-point methods reduces the number of iterations.

• 제어로봇시스템학회:학술대회논문집
• /
• 1997.10a
• /
• pp.1473-1476
• /
• 1997

This paper presents a scheme for continuous-time fuzzy modelling of nonlinear systems, based on the adjustment technique and the genetic algorithm technque. The fuzzy model is characterized by fuzzy "If-then" rules whcih represent locally linear input-output relations whose consequence part is defined as subsystem of a nonlinear system. To compute the final output and deal with the initialization and unmeasurable signal problems in on-line estimatio of the fuzzy model, a discrete-time model is obtaned. Then the parameters of both the premis and consequence of the fuzzy model are adjusted on-line by a genetic algorithm. A simulation work is carried out to demonstrate the effectiveness of the proposed method.ed method.

• Journal of Institute of Control, Robotics and Systems
• /
• v.2 no.4
• /
• pp.318-323
• /
• 1996

The speed of SR(Switched Reluctance) motor can be controlled by switching angle. However, since the relation between speed and switching is nonlinear, it is difficult for simple adjustment schemes to achieve the desired performances. In this paper, an error.feedback nonlinear compensator with robustness is proposed for improving the performances of the switching angle controlled SR motor. The proposed controller consists of integral type control and relay type control. The integral type controller which operates regulation, is derived by the steady.state I/O(input/output) map and the relay type controller which works tracking, is designed by Lyapunov stability theory. The validities of the proposed controller are confirmed with the experimental results.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.30 no.6
• /
• pp.1044-1055
• /
• 1997

To find out generating mechanism of eddies in the polar frontal zone of the East Sea, we carried out a series of numerical experiments using the nonlinear $1^{1/2}-layer$ model allowing the effect of the polar front. We assumed the polar front at about $39^{\circ}N$ in zonal direction with the cold water region in the northern part and the warm water region in the southern part of the model ocean. To examine the effect of the frontal motion without the influence of the Tsushima Current from the beginning of the geostrophic adjustment, the initial state of the model ocean was assumed motionless. Eastward current was caused by the geostrophic adjustment process in the polar frontal zone that induced a steady northward coastal current along the Korean coast to satisfy the mass continuity. The overshooting of this coastal current acted as an initial disturbance of the zonal flow field which caused meanders and eddies. The spatial scales of eddies were in good agreement with the baroclinic instability theory.