• Journal of Korean Institute of Industrial Engineers
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• v.12 no.1
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• pp.43-48
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• 1986

In this paper, the one period multi-item inventory model is considered in which it is required to determine the production quantity and selling price of each item which maximize the probability of realizing predetermined level of profit. The objective function of this model is the sum of weighted probabilities which represent the possibility of obtaining the predetermined level of profit for each item. Budget constraint, inventory site constraint and constraints of price are considered. Finally this paper shows a numerical example in which random demand of each item has exponential distribution.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1863-1871
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• 2016

This paper presents an application of fractional order controller for the control of multi input multi output twin rotor aerodynamic system. Dynamics of the considered system are highly nonlinear and there exists a significant cross-coupling between the horizontal and vertical axes (pitch & yaw). In this paper, a fractional order model of twin rotor aerodynamic system is identified using input output data from nonlinear system. Based upon identified fractional order model, a fractional order PID controller is designed to control the angular position of level bar of twin rotor aerodynamic system. The parameters of controller are tuned using Nelder-Mead optimization and compared with particle swarm optimization techniques. Simulation results on the nonlinear model show a significant improvement in the performance of fractional order PID controller as compared to a classical PID controller.

• IE interfaces
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• v.21 no.4
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• pp.444-455
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• 2008

In the present manufacturing environment, the appropriate decision making strategy has a significance and it should count on the fast-changing demand of customers. This research derives the optimal levels of the decision variables affecting the inventory related performance in multi-stage supply chain by using simulation and genetic algorithm. Simulation model helps analyze the customer service level of the supply chain computationally and the genetic algorithm searches the optimal solutions by interaction with the simulation model. Our experiments show that the integration approach of the genetic algorithm with a simulation model is effective in finding the solutions that achieve predefined target service levels.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.918-922
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• 2006

The purpose of this study is development of operation model for flood control of multi-reservoir in river basin, which can provide the best decision of reservoir release in timely and appropriately manner using CSUDP. For verification and validation of the developed system, the Gum River Basin was selected, which has 82 rainfall gauging stations, 28 water level gauging and 2 multi-purpose reservoirs which can control flood. There was a successful simulation of the developed model and system, using the real-time data from the Han River Basin Flood Forecast Center. Specially, case study for '1995 flood was performed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.11
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• pp.4118-4136
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• 2014

To preserve the spatial consistency of low-level features, generalized Riesz-wavelet transform (GRWT) is adopted for fusing multi-modality images. The proposed method can capture the directional image structure arbitrarily by exploiting a suitable parameterization fusion model and additional structural information. Its fusion patterns are controlled by a heuristic fusion model based on image phase and coherence features. It can explore and keep the structural information efficiently and consistently. A performance analysis of the proposed method applied to real-world images demonstrates that it is competitive with the state-of-art fusion methods, especially in combining structural information.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.5
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• pp.91-98
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• 2012

Since the major cellular data service providers in U.S, Japan as well as in Korea started the LTE (Long Term Evolution) service, there has been more strong need for the methods that can accurately measure the MIMO (Multi Input-Multi Output) OTA (Over The Air) performance of LTE handsets because the performance of the MIMO antenna determines the data throughput in the downlink. In this paper, the hand effect on the MIMO antenna performance is analyzed by numerically and experimentally. The hand effect on the LTE mobile handset is analyzed by measuring the link level performance in the MIMO OTA system.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.4
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• pp.386-394
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• 2012

Recent trends in the flexible manufacturing systems are morphing cell control for the shop-wide production operation system and providing the integrated operation and execution system together with vendor-specific FMC/FMS platform. In these requirements, the shop-floor level operation system plays a role of coordinating the control activity of each cell, and has to provide flexibility for the complexity of mixed operations of various cells. This paper suggests a system architecture for the mixed environments of multi-cells and job shop, its corresponding enabling technologies based on comparative studies with other related studies and commercialized systems. This approach includes a process definition model considering the integration with upper BOM-BOP and external service modules, and reconfigurable device-level interface which provides dynamic interconnections with machine tools and cell controllers. The function modules and their implementation results are also described to provide the feasibility of the proposed approaches as the flexible shop-floor operation system for the multi-cell environments.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.2
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• pp.154-173
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• 2010

Database outsourcing is unavoidable in the near future. In the scenario of data stream outsourcing, the data owner continuously publishes the latest data and associated authentication information through a service provider. Clients may register queries to the service provider and verify the result's correctness, utilizing the additional authentication information. Research on On-line Stream Analytics (OLSA) is motivated by extending the data cube technology for higher multi-level abstraction on the low-level-abstracted data streams. Existing work on OLSA fails to consider the issue of database outsourcing, while previous work on stream authentication does not support OLSA. To close this gap and solve the problem of OLSA query authentication while outsourcing data streams, we propose MDAHRB and MDAHB, two multi-dimensional authentication approaches. They are based on the general data model for OLSA, the stream cube. First, we improve the data structure of the H-tree, which is used to store the stream cube. Then, we design and implement two authentication schemes based on the improved H-trees, the HRB- and HB-trees, in accordance with the main stream query authentication framework for database outsourcing. Along with a cost models analysis, consistent with state-of-the-art cost metrics, an experimental evaluation is performed on a real data set. It exhibits that both MDAHRB and MDAHB are feasible for authenticating OLSA queries, while MDAHRB is more scalable.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.6
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• pp.556-561
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• 2013

Interest in spin-torque oscillators (STOs) has been increasing due to their potential use in communication devices. In particular the magnetic tunnel junction-based STO (MTJ-STO) with high perpendicular anisotropy is gaining attention since it can generate high output power. In this paper, a circuit-level model for an in-plane magnetized MTJ-STO with partial perpendicular anisotropy is proposed. The model includes the perpendicular torque and the shift field for more accurate modeling. The bias voltage dependence of perpendicular torque is represented as quadratic. The model is written in Verilog-A, and simulated using HSPICE simulator with a current-mirror circuit and a multi-stage wideband amplifier. The simulation results show the proposed model can accurately replicate the experimental data such that the power increases and the frequency decreases as the value of the perpendicular anisotropy gets close to the value of the demagnetizing field.

• Computational Structural Engineering : An International Journal
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• v.3 no.1
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• pp.1-7
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• 2003

For system identification of large structures, it is not practical to identify the entire structure due to the prohibitive computational time and difficulty in numerical convergence. This paper explores the possibility of performing system identification at substructure level, taking advantage of reduction in both the number of unknowns and the number of degrees of freedom involved. Another advantage is that different portions (substructures) of a structural system can be identified independently and even concurrently with parallel computing. Two substructural identification methods are formulated on the basis whether substructural approach is used to obtain first-order or second-order model. For substructural first-order model, identification at the substructure level will be performed by means of the Observer/Kalman filter Identification (OKID) and the Eigensystem Realization Algorithm (ERA) whereas identification at the global level will be performed to obtain second-order model in order to evaluate the system's stiffness and mass parameters. In the case of substructural second-order model, identification will be performed at the substructure level throughout the identification process. The efficiency of the proposed technique is shown by numerical examples for multi-storey shear buildings subjected to random forces, taking into consideration the effects of noisy measurement data. The results indicate that both the proposed methods are effective and efficient for damage identification of large structures.