• Journal of the Korea Safety Management & Science
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• v.16 no.4
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• pp.323-330
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• 2014

Various inventory control theories have tried to modelling and analyzing supply chains by using quantitative methods and characterization of optimal control policies. However, despite of various efforts in this research filed, the existing models cannot afford to be applied to the realistic problems. The most unrealistic assumption for these models is customer demand. Most of previous researches assume that the customer demand is stationary with a known distribution, whereas, in reality, the customer demand is not known a priori and changes over time. In this paper, we propose a reinforcement learning based adaptive echelon base-stock inventory control policy for a multi-stage, serial supply chain with non-stationary customer demand under the service level constraint. Using various simulation experiments, we prove that the proposed inventory control policy can meet the target service level quite well under various experimental environments.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.04a
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• pp.233-240
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• 2001

Artificial neural networks(ANN) have been exploited where the relationship among information is very complicated and nonlinear. It is appropriate to computerize the information and knowledge used in the preliminary design stage where it lacks of formality of representation of designers' experience and intuition. However, most designers start the preliminary design stage with very little information. Therefore, the ANN model for this stage must be designed to have input much less than output. This case usually causes big troubles such as in learning time, convergence and reliability of solutions. To address this problem, this paper proposes multi-level neural networks for progressive structural design considering that all the design information can not be obtained at a time but are growing gradually. The use of multi-level networks developed in this paper has been proved its validity by applying it to the preliminary design of cable-stayed bridges.

• Journal of Korea Society of Digital Industry and Information Management
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• v.5 no.4
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• pp.179-187
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• 2009

In this paper, an efficient multi-level successive elimination algorithm using the locality in block was proposed for motion estimation. If SAD(sum of absolute difference) is calculated from large absolute difference values to small absolute difference values, SAD is increased rapidly. So, partial distortion elimination in SAD calculation can be done very early. Hence, the computations of SAD calculation can be reduced. In this paper, an efficient algorithm to calculate SAD from large absolute difference values to small absolute difference values by using the locality in block. Experimental results show that the proposed algorithm is an efficient algorithm with 100% motion estimation accuracy for the motion estimation of motion vectors.

• Korean Management Science Review
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• v.24 no.2
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• pp.73-80
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• 2007

Robust Design(RD) is a cost-effective methodology to determine the optimal settings of control factors that make a product performance insensitive to the influence of noise factors. To better facilitate the robust design optimization, a dual response surface approach, which models both the process mean and standard deviation as separate response surfaces, has been successfully accepted by researchers and practitioners. However, the construction of response surface approximations has been limited to problems with only a few variables, mainly due to an excessive number of experimental runs necessary to fit sufficiently accurate models. In this regard, an innovative response surface approach has been proposed to investigate robust design optimization problems with larger number of variables. Response surfaces for process mean and standard deviation are partitioned and estimated based on the multi-level approximation method, which may reduce the number of experimental runs necessary for fitting response surface models to a great extent. The applicability and usefulness of proposed approach have been demonstrated through an illustrative example.

• Journal of the Korea Safety Management & Science
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• v.11 no.3
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• pp.139-148
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• 2009

In a real-life supply chain environment, demand forecasting is usually represented by probabilistic distributions due to the uncertainty inherent in customer demands. However, the customer demand used for an actual supply chain planning is a single deterministic value for each of periods. In this paper we study the choice of single demand value among of the given customer demand distribution for a period to be used in the supply chain planning. This paper considers distributed multi-echelon supply chain and the objective function of this paper is to minimize the total costs, that is the sum of holding and backorder costs over the distribution network under the service level constraint, by using demand selection scheme. Some useful findings are derived from various simulation-based experiments.

• Journal of the Microelectronics and Packaging Society
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• v.9 no.3
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• pp.1-6
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• 2002

A low temperature process technology of copper thin films has been developed by a chemical vapor deposition technology for multi-level metallzations in ULSI fabrication. The copper films were deposited on TiN/Si substrates in helium atmosphere with the substrate temperature between $130^{\circ}C$ and $250^{\circ}C$. In order to get more reliable metallizations, effects on the post-annealing treatment to the electrical properties of the copper films have been investigated. The Cu films were annealed at the $5 \times10^{-6}$ Torr vacuum condition and the electrical resistivity and the nano-structures were measured for the Cu films. The electrical resistivity of Cu films shown to be reduced by the post-annealing. The electrical resistivity of 2.0 $\mu \Omega \cdot \textrm{cm}$ was obtained for the sample deposited at the substrate temperature of $180^{\circ}C$ after vacuum annealed at $300^{\circ}C$. The resistivity variations of the films was not exactly matched with the size of the nano-structures of the copper grains, but more depended on the contamination of the copper films.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.114-119
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• 2004

Floating marina has been interests as an alternative to the facilities for recreational boats because of its cost effectivenes and less environmental conflicts. For tile present research, a square floating marina with a length of 400m and draft of 5m was used. This marina can be extended to 800m by putting anotjer one together. Tidal field around tile marina was simulated using a multi-level finite difference method. Tidal motion was assumed sinusoidal in a closed rectangular bay. Velocities and residual current were investigated for two cases of single marina and two marinas installed in tile bay. It was found that the horizontal velocity fields from the water surface to the structure bottom around tile marina were affected. In the marina basin, magnitude of velocity was reduced considerably but overall quality of water circulation was preserved even after two marina were installed.

• Proceedings of the IEEK Conference
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• 2003.11c
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• pp.281-284
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• 2003

Multi-code CDMA is an appropriate scheme for transmitting high rate data. However, dynamic range of the signal is large, and power amplifier with good linearity is required. Code select CDMA (CS/CDMA) is a variation of multi-code CDMA scheme that ensures constant amplitude transmission. In CS/CDMA input data selects multiple orthogonal codes, and sum of these selected codes are MPSK modulated to convert multi-level symbol into different carrier phases. CS/CDMA system employs level clipping to limit the number of levels at the output symbol to avoid hish density of signal constellation. In our previous work we showed that by encoding input data of CS/CDMA amplitude of the output symbol can be made constant. With this coding scheme, level clipping is not necessary and the output signal can be BPSK modulated for transmission. In this paper we show that the constant amplitude coded(CA-) CS/CDMA transmitter can be implemented using only logic gates, and the hardware complexity is very low. In the proposed transmitter architecture there is no apparent redundant encoder block which plays a major role in the constant amplitude coded CS/CDMA.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.11a
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• pp.256-257
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• 2018

This paper deals with the path-following control for marine surface vehicles with underactuated characteristics. In consideration of practical limitations of actuators, an improved DVS(dynamic virtual ship) guidance algorithm is proposed with the multi-level DVS optionally selected to be tracked. To address the output-feedback control issue, an adaptive FLS(fuzzy logical systems) is devised to online approximate the kinematic states. Based on that observing framework, the path-following control law is thereafter derived. Simulations testify effectiveness of the proposed scheme

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.742-745
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• 2005

This paper describes a simple pseudo-random carrier modulation technique for the acoustic noise reduction of the three phase multi-level inverter based motor drives. The proposed method generates a new pseudo-random carrier by randomly synthesizing a carrier with fixed frequency and a carrier with opposition phase. To confirm the validity of the proposed method, a 130v three-phase multi-level inverter was Implemented and tested. The experimental results show that the output line voltage and acoustic noise harmonics spectra of an inverter have broadening effect of harmonics, as only simple synthesis of fixed frequency carries.