• Journal of Navigation and Port Research
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• 제31권10호
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• pp.869-877
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• 2007

This paper proposes a realtime scheduling method using local search algorithm for non-crossable yard cranes in automated container terminal. To take into consideration the dynamic property of yard crane operation and satisfy the real time constraint, the proposed method repeatedly builds crane schedule for the jobs in a fixed length look-ahead horizon whenever a new job is requested In addition, the proposed method enables the co-operation between yard cranes through prior re-handling and re-positioning in order to resolve the workload imbalance problem between the two cranes, which is one of the primary causes that lower the performance of yard cranes. Simulation-based experiments have shown that the proposed method outperforms the heuristic based methods, and the cooperation scheme contributes a lot to the performance improvement.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제14권5호
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• pp.1093-1102
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• 2010

Principal component analysis (PCA) is a well-known method for dimension reduction while maintaining most of the variation in data. Although PCA has been applied to many areas successfully, it is sensitive to outliers. Several variants of PCA have been proposed to resolve the problem and, among the variants, robust fuzzy PCA (RF-PCA) demonstrated promising results. RF-PCA uses fuzzy memberships to reduce the noise sensitivity. However, there are also problems in RF-PCA and the convergence property is one of them. RF-PCA uses two different objective functions to update memberships and principal components, which is the main reason of the lack of convergence property. The difference between two functions also slows the convergence and deteriorates the solutions of RF-PCA. In this paper, a variant of RF-PCA, called RF-PCA2, is proposed. RF-PCA2 uses an integrated objective function both for memberships and principal components. By using alternating optimization, RF-PCA2 is guaranteed to converge on a local optimum. Furthermore, RF-PCA2 converges faster than RF-PCA and the solutions found are more similar to the desired solutions than those of RF-PCA. Experimental results also support this.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제18권11호
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• pp.2613-2620
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• 2014

In this paper, we consider a full duplexing (FD) wireless cellular network where a central base station (BS) works in the FD mode while the downlink (DL) and uplink (UL) users work in the time division duplexing (TDD) mode. Since this FD system induces the inter-user interference from UL user to DL user, the main challenge for maximizing the system performances is user scheduling that makes a pair of DL user and UL user to use the same radio resource simultaneously. We formulate an optimization problem for user pairing to maximize the cell capacity and propose a suboptimal user scheduling algorithm with low complexity. This scheduling algorithm is designed in a way where the DL user with a better signal quality has a higher priority to choose its UL user that causes less interference. Simulation results show that the FD system using the proposed user scheduling algorithm achieves the optimal performance and significantly outperforms the conventional TDD system in terms of the cell capacity.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제22권4호
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• pp.602-610
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• 2018

The model predictive control is an effective method to optimize the current control input that predicts the current control state and the future error using the predictive model of the control system when the reference trajectory is known. Since the control input can not have a physically infinitely large value, a predictive controller design with constraints should be considered. In addition, the reference model $A_r$ and the weight matrices Q, R that determine the control performance of the predictive controller are not optimized as arbitrarily designated should be considered in the controller design. In this study, we construct a predictive controller of a mobile robot by transforming it into a quadratic programming problem with constraints, The control performance of the mobile robot can be improved by optimizing the control parameters of the predictive controller that determines the control performance of the mobile robot using genetic algorithm. Through the computer simulation, the superiority of the proposed method is confirmed by comparing with the existing method.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제22권7호
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• pp.943-948
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• 2018

In this paper, we propose a hybrid approach of combining $A^*$ and Genetic algorithm in the path search problem. In $A^*$, the cost from a start node to the intermediate node is optimized in principle but the path from that intermediate node to the goal node is generated and tested based on the cumulated cost and the next node in a priority queue is chosen to be tested. In that process, we adopt the genetic algorithm principle in that the group of nodes to generate the next node from an intermediate node is tested by its fitness function. Top two nodes are selected to use crossover or mutation operation to generate the next generation. If generated nodes are qualified, those nodes are inserted to the priority queue. The proposed method is compared with the original sequential selection and the random selection of the next searching path in $A^*$ algorithm and the result verifies the superiority of the proposed method.

• Journal of KIISE:Computer Systems and Theory
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• 제30권10호
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• pp.595-602
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• 2003

This Paper presents an efficient hybrid techniques for a standard cell placement. The prototype tool adopts a middle-down methodology in which an n${\times}$m grid is imposed over the layout area and cells are assigned to bins forming a global placement. The optimization technique applied in this phase is based on the Relaxation-Based Local Search (RBLS) framework [12］in which a combinatorial search mechanism is driven by an analytical engine. This enables a more global view of the problem and results in complex modifications of the placement in a single search“move.”Details of this approach including a novel placement legalization procedure are presented. When a global placement converges, a detailed placement is formed and further optimized by the optimal interleaving technique[13］. Experimental results on MCNC benchmarking circuits are presented and compared with the Feng Shui's results in［14］. Solution Qualifies are almost the same as the Feng Shui's results.

• Journal of KIISE:Software and Applications
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• 제33권7호
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• pp.624-635
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• 2006

This paper applies simulated annealing algorithm to the problem of generating a plan for intra-block remarshalling with multiple transfer cranes. Intra-block remarshalling refers to the task of rearranging containers scattered around within a block into certain designated target areas of the block so that they can be efficiently loaded onto a ship. In generating a remarshalling plan, the predetermined container loading sequence should be considered carefully to avoid re-handlings that may delay the loading operations. In addition, the required time for the remarshalling operation itself should be minimized. A candidate solution in our search space specifies target locations of the containers to be rearranged. A candidate solution is evaluated by deriving a container moving plan and estimating the time needed to execute the plan using two cranes with minimum interference. Simulation experiments have shown that our method can generate efficient remarshalling plans in various situations.

• Transactions on Electrical and Electronic Materials
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• 제5권1호
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• pp.1-6
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• 2004

Zinc sulfide is a semiconductor with wide band gap and high refractive index and hence promising material to be used as ARC on commercial silicon solar cells. Uniform deposition of zinc sulfide (ZnS) by using chemical bath deposition (CBD) method over a large area of silicon surface is an emerging field of research because ZnS film can be used as a low cost antireflection coating (ARC). The main problem of the CBD bath process is the huge amount of precipitation that occurs during heterogeneous reaction leading to hamper the rate of deposition as well as uniformity and chemical stoichiometry of deposited film. Molar concentration of thiorea plays an important role in varying the percentage of reflectance and refractive index of as-deposited CBD ZnS film. Desirable rate of film deposition (19.6 ${\AA}$ / min), film uniformity (Std. dev. < 1.8), high value of refractive index (2.35), low reflectance (0.655) have been achieved with proper optimization of ZnS bath. Decrease in refractive index of CBD ZnS film due to high temperature treatment in air ambiance has been pointed out in this paper. Solar cells of conversion efficiency 13.8 ％ have been successfully achieved with a large area (103 mm ${\times}$ 103 mm) mono-crystalline silicon wafers by using CBD ZnS antireflection coating in this modified approach.

• The KIPS Transactions:PartD
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• 제15D권1호
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• pp.99-106
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• 2008

Recently developed compilers perform some optimizations in order to speed up the execution time of source program. These optimizations require the reordering of the sequence of program statements. This reordering does not give any problems in a single-threaded program. However, the reordering gives some significant errors in a multi-threaded program. State-of-the-art model checkers such as JavaPathfinder do not consider the reordering resulted in the optimization step in a compiler since they just consider a single memory model. In this paper, we develop a new verification tool to verify Java source program based on Java Memory Model. And our tool is capable of handling the reordering in verifying Java programs. As a result, our tool finds an error in the test program which is not revealed with the traditional model checker JavaPathFinder.

• KIPS Transactions on Computer and Communication Systems
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• 제7권8호
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• pp.203-210
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• 2018

Mobile traffic is increasing consistently, and mobile carriers are becoming more and more hard to meet this ever-increasing mobile traffic demand by means of additional installation of base stations. To overcome this problem, heterogeneous networks, which can reuse space and frequency by installing small cells such as femto cells in existing macro cells, were introduced. However, existing macro cell users are difficult to increase the spectral efficiency without the cooperation of femto owners. Femto owners are also reluctant to accommodate other mobile stations in their femto stations without proper incentive. In this paper, a method of obtaining the optimal incentive is proposed, which adopts a utility function based on the logarithm of throughput of mobile stations, and the incentive is calculated to maximize the utility of the entire network.