• 제어로봇시스템학회논문지
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• 제4권6호
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• pp.713-721
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• 1998

In this paper a new modeling and an optimal pole-placement control for the suspension system of Macpherson type are investigated. The rotational motion of the unsprung mass is emphasized in the new modeling. The two generalized coordinates selected in the new model are the vortical displacement of sprung mass and the angular displacement of control arm. Both variables are measured from their static equilibrium points. It is shown that the conventional model is a special case of the new model since the transfer function of the new model coincides with that of the conventional one if the lower support point of the shock absorber is located at the mass center of the unsprung mass. It is also shown that the resonance frequencies of the new model agree better with experimental results. Therefore, the new model is more general in the sense that it Provides an extra degree of freedom in determining the plant model for control system design. An optimal pole-placement control which combines LQ control and pole-placement technique is applied to the new model. Simulations are provided.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 춘계학술대회 논문집 반도체 재료 센서 박막재료 전자세라믹스
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• pp.30-33
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• 2004

Shallow p+-n junctions were formed by low-energy ion implantation and dual-step annealing processes The dopant implantation was performed into the crystalline substrates using $BF_2$ ions. The annealing was performed with a rapid thermal processor and a furnace. FA+RTA annealing sequence exhibited better junction characteristics than RTA+FA thermal cycle from the viewpoint of junction depth. A new simulator is designed to model boron diffusion in silicon, which is especially useful for analyzing the annealing process subsequent to ion implantation. The model which is used in this simulator takes into account nonequilibrium diffusion, reactions of point defects, and defect-dopant pairs considering their charge states, and the dopant inactivation by introducing a boron clustering reaction. Using a resonable parameter values, the simulator covers not only the equilibrium diffusion conditions but also the nonequilibrium post-implantation diffusion. Using initial conditions and boundary conditions, coupled diffusion equation is solved successfully. The simulator reproduced experimental data successfully.

• Industrial Engineering and Management Systems
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• 제12권3호
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• pp.207-223
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• 2013

Revenue management (RM) has been widely used to model products characterized as perishable. Classical RM model assumed that price is the sole factor in the model. Thus price adjustment becomes a crucial and costly factor in business. In this paper, an optimal pricing model is developed based on minimization of soft customer cost, one kind of price adjustment cost and is solved by Lagrange multiplier method. It is formed by expected discounted revenue/bid price integrating quantity-based RM and pricing-based RM. Quantity-based RM consists of two capacity models, namely, booking limit and overbooking. Booking limit, built by assuming uncertain customer arrival, decides the optimal capacity allocation for two market segments. Overbooking determines the level of accepted order exceeding capacity to anticipate probability of cancellation. Furthermore, pricing-based RM models occupancy/demand rate influenced by internal and competitor price changes. In this paper, a mathematical model based on game theoretic approach is developed for two conditions of deterministic and stochastic demand. Based on the equilibrium point, the best strategy for both hotels can be determined.

• 한국멀티미디어학회논문지
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• 제3권4호
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• pp.416-423
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• 2000

기존 Kohonen의 자기조직화 지도(self-organizing feature map)는 학습시 많은 입력 패턴이 필요하며 이에 따른 학습 시간 역시 증가하는 단점이 있다. 이러한 단점을 보완하기 위해 B. Bavarian은 위상학적 위치에 따라 각기 다른 학습률(learning rate)을 갖도록 하였으나 자기조직화가 정밀하게 되지 않는 단점을 갖고 있다. 본 논문에서는 자기조직화 지도의 학습시 계산량이 많은 가우시안 함수를 근사곡선(approximate curve)으로 변형하여 수렴속도를 향상시켰고 학습 횟수에 따라 근사곡선의 폭을 동적으로 변화시킴으로써 자기조직화지도의 수렴도를 개선하였다.

• 한국지능시스템학회논문지
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• 제9권6호
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• pp.598-604
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• 1999

본 논문에서는 능동형자기베어링(Active Magnetic Bearing AMB)시스템의 제어를 위한 새로운 퍼지제어 알고리즘을 제안한다. 이 방법은 AMB 시스템의 비선형 특성을 효과적으로 다루기 위하여 Joh등[4,5]이 제안한 LMI에 근거한 PDC 알고리즘과 퍼지 싱글톤을 사용하는 Mamdani형의 퍼지제어기를 복합한다. 이들은 각각 fine mode control과 coarse mode control이라고 구분하였다. coarse mode control은 회전축의 위치에러가 큰 경우 빠른 중심복귀 응답특성을 보이며 fine mode control은 회전축의 위치에러가 작을 때 요구되는 과도응답특성을 제공한다. 본 논에서 제안된 방법은 그성능을 입증하기 위하여 AMB 시스템의 제어에 적용되었으며 선형제어기와 일반적인 PDC 알고리즘으로 제어된 결과와의 비교를 통해 제안된 방법의 우수성을 보인다.

• Bulletin of the Korean Chemical Society
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• 제26권1호
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• pp.119-126
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• 2005

The geometrical parameters, vibrational frequencies, and relative energies of H$_2$(A$_{n+1}$X$_{2n}$)H$_2$ (A=C or Si, X=O or S, n = 1-2) oligomers have been investigated using high level ab initio quantum mechanical techniques with large basis sets. The equilibrium geometries have been optimized at the self-consistent field (SCF), the coupled cluster with single and double excitation (CCSD), and the CCSD with connected triple excitations [CCSD(T)] levels of theory. The highest level of theory employed in this study is cc-pVTZ CCSD(T). Harmonic vibrational frequencies and IR intensities are also determined at the SCF level of theory with various basis sets and confirm that all the optimized geometries are true minima. Also zero-point vibrational energies have been considered to predict the dimerization and the relative energies.

• 한국자동차공학회논문집
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• 제22권3호
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• pp.130-135
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• 2014

In this paper, a new estimation method is proposed to calculate steering rack axial force using a 3 dimensional tire mesh model when a car is standing on the road. This model is established by considering changes of camber angle and contact patch between the tires and the ground according to steering angle. The steering rack bar axial force is estimated based on the static equilibrium equations of forces and moments. A tire friction force is supposed to act on the center point of the contact patch, and the proportional coefficient of friction depending on contact patch is suggested. Using the proposed estimation method, rack axial force sensitivity analysis is evaluated according to changes of suspension geometry. Then optimal motor power of Motor Driven Power Steering(MDPS) is evaluated using suggested rack forces.

• Tribology and Lubricants
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• 제24권6호
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• pp.378-385
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• 2008

In foil bearings, the friction between bumps and their mating surfaces is the major factor which exerts great influence on the bearing performance. From this point of view, many efforts have been made to improve the understanding of the influence of the friction on the foil bearing performance by developing a number of analytical models. However, most of them did not consider the hysteretic behavior of the foil structure resulting from the friction. The present work developed the static structural model in which hysteretic behavior of the friction was considered. The foil structure was modeled using finite element method and the algorithm which determines the conditions of the contact nodes and the directions of the friction forces was used to take into account the friction. The developed model was integrated into the foil bearing prediction code to investigate the effects of the friction on the static performance of the bearing. The results of analysis show that multiple static equilibrium positions are presented for the one static load under the influence of the friction, inferring its great effects on the dynamic performance. However, the effect of friction on the minimum film thickness which determines load capacity of the bearing is negligible.

• 한국소음진동공학회논문집
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• 제13권12호
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• pp.903-910
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• 2003

A two-degree-of-freedom model is suggested to describe basic dynamical behaviors of the interaction between the pad and the disc of a disc brake system. Although a pad (and a disc) has many modes of vibration in practice, only one mode of each component Is considered. In this paper, a linear analysis is performed by means of the stability analysis to show various conditions for the system to become unstable, and is based on the assumption that the existence of limit cycle (this corresponds to an unstable equilibrium point inside the limit cycle) represents the squeal state of the disc brake system. The results of the stability analysis show that the damping of the disc is as much Important as that of the pad, whereas the damping of the pad only is considered In most practical situations.

• 한국산업융합학회 논문집
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• 제2권2호
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• pp.35-39
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• 1999

Results of two-part wedge analysis and centrifuge test executed by Zornberg et al. were compared for geotextile-reinforced slope stability. For two-part wedge analysis results of two cases, a frictional case considering internal friction of soil as interwedge friction and a nonfrictional case not considering, were also compared and evaluated. The analysis was based on limit equilibrium and two-part wedge was divided into slices as many as the number of geotextiles to obtain a maximum tension distribution mobilized in reinforcements. A significant observation was that the distribution was a triangular shape with maximum tension of geotextile at a transit point of interwedge. The number of geotextiles and failure surface of frictional case were reasonable and more comparable to results of the centrifuge tests than those of nonfrictional case. Therefore it can be said that two-part wedge analysis is recommendable for design analysis of reinforced slopes if an interwedge angle is regarded to be an angle of internal friction in soil.