• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.12
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• pp.5212-5230
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• 2016

How to determine the right number of small base stations to activate in multi-cell uplinks to match traffic from a fixed quantity of K users is an open question. This paper analyses the uplink cooperative that jointly receives base stations activation to explore this question. This paper is different from existing works only consider transmitting power as optimization objective function. The global objective function is formulated as a summation of two terms: transmitting power for data and coordinated overhead for control. Then, the joint base stations activation and beamforming problem is formulated as a mixed integer second order cone optimization. To solve this problem, we develop two polynomial-time distributed methods. Method one is a two-stage solution which activates no more than K small base stations (SBSs). Method two is a heuristic algorithm by dual decomposition to MI-SOCP that activates more SBSs to obtain multiple-antennae diversity gains. Thanks to the parallel computation for each node, our methods are more computationally efficient. The strengths and weaknesses of these two proposed two algorithms are also compared using numerical results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.717-720
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• 2000

Event-driven communication protocols such as CAN(Controller Area Network) have inherent packet delays due to the contention process for the use of network medium. These delays are stochastic in nature because most packets arrive at random time instants. The stochastic property of the delay adversely influences the control system's performance in terms of stability, responsiveness and steady-state error. Another problem for safety-critical application such as brake-by-wire systems is the reliability of the communication modules that can fail abruptly. This paper deals with two methods to overcome the above problems : (i) scheduling method that can maintain packet delays under some acceptable level, and (ii) redundancy management of communication modules that prescribes dual-redundancy modules' behavior when one of them fails.

• Journal of the Korean Society of Industry Convergence
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• v.20 no.1
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• pp.49-55
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• 2017

This study proposes a new approach to Control and trajectory generation of a 8 DOF human robot arm with computational complexity and singularity problem. To deal with such problems, analytical methods for a redundant robot arm have been researched to enhance the performance of research, we propose an analytical kinematics algorithm for a 8 DOF bipped dual robot arm. Using this algorithm, it is possible to generate a trajectory passing through the singular points and intuitively move the elbow without regarding to the end-effector pose. Performance of the proposed algorithm was verified by simulation test with various conditions. It has been verified that the trajectory planning using this algorithm.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.2
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• pp.670-683
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• 2016

Network coding, as a new technique to improve the throughput, is studied combined with multi-relay model in this paper to address the challenges of long distance and power limit in deep space communication. First, an amplify-and-forward relaying approach based on analog network coding (AFNC) is proposed in multi-relay network to improve the capacity for deep space communication system, where multiple relays are introduced to overcome the long distance link loss. The design of amplification coefficients is mathematically formulated as the optimization problem of maximizing SNR under sum-power constraint over relays. Then for a dual-hop relay network with a single source, the optimal amplification coefficients are derived when the multiple relays introduce non-coherent noise. Through theoretic analysis and simulation, it is shown that our approach can achieve the maximum transmission rate and perform better over single link transmission for deep space communication.

• Journal of the Institute of Convergence Signal Processing
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• v.3 no.4
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• pp.49-56
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• 2002

In this paper, a new controller using non-linear compensator for position control is presented, which we can satisfy the given specifications more easily than the existing one. We suggest an improved PDFE(Integral with Proportional-Derivative-plus-Feedforward) controller by which both phase margin and bandwidth are controlled simultaneously in the controller design problem. Replacing the feed forward term in the PDFF system with a CDIDF(Complex Dual Input Describing Function), the desired phase margin is obtained without diminishing the bandwidth of the closed loop system. The effectiveness of the proposed controller is confirmed through simulations and experiments. As The results of these, we know that it is possible to adjust overall specifications by varying parameters in the improved PDFF system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.2
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• pp.33-38
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• 2010

Recently, photovoltaic generator system is widely extended by energy policy of the government. Add to this, high efficiency of photocell power generation is steady needed to sun tracking method. However sun tracking method is not widely extended by insufficiency of tracking technology. As method of solving this problem, this paper applied sunlight sensor and neural network control algorithm for maximum power tracking of sun photocell. Sun tracking sensor consists of one upright square pole and form light sensor of east, west, south, north on flat board. Sun tracking dual axes control is operated respectively by two motor. Motor control input is calculated by neural network control algorithm. The function of proposed control method is verified by sun tracking experiment of photocell generation. The sun tracking method of this paper is increased 32[%] efficiency more than fixed method.

• Archives of Plastic Surgery
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• v.34 no.1
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• pp.93-98
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• 2007

Purpose: Many options are available for the incision and pocket selection in breast augmentation. Each method has its advantages and disadvantages. To leave an invisible operation scar and to achieve easier pocket dissection by the central location of the incision on the breast, we made a transareolar-perinipple incision. To overcome the disadvantages of the transareolar incision, originally advocated by Pitanguy in 1973, we modified the direction of incision line and dissection plane. Methods: To avoid the injury of 4th intercostal nerve responsible for nipple sensation, we made perinipple incision on the medial side of the nipple instead of trans-nipple incision and made the transareolar incision as 11-5 o'clock on the left side and 1-7 o'clock on the right side instead of 3-9 o'clock on both sides. To avoid the possible infection and breast feeding problem caused by the injury to the lactiferous duct, and the possible implant hernia caused by the incisions lying on a same plane of pocket dissection, we made a subcutaneous dissection just above the breast tissue medially down to the bottom of breast tissue and made a subglandular or subfascial pocket, which may avoid the injury of lactiferous duct and create different planes for skin incision and pocket dissection. Other advantages of the transareolar-perinipple incision include easier pocket dissection, less chance of hematoma, and as a result less postoperative pain because of the central location of the approach which allow finger dissection and meticulous bleeding control with direct vision, without any specialized instrument such as an endoscope or long mammary dissectors. As for pocket selection, we made dual pockets. We prefer subglandular or subfascial pocket. Also, we made a subpectoral pocket in the upper 1/4 of the pocket to add more volume on the upper part of the augmented breast, which can make aesthetically more desirable breasts in thin Asian women with small breasts. Possible disadvantages of our method are subclinical infection and scar widening, which could be overcome by meticulous operation techniques, antibiotic therapy, and intradermal tattooing. Results: From September, 2003 to August, 2005, 12 patients underwent breast augmentation using round smooth surface saline implants by our method. During the mean follow-up period of 13 months, there were no complications such as infection, hematoma, capsular contracture, and sensory change of nipple, and results were satisfactory. Conclusion: We suggest breast augmentation via transareolar-perinipple incision and dual pockets(subpectoral-subglandular or subfascial) as a valuable method in thin oriental women with small breasts.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.1
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• pp.14-22
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• 2010

Hybrid Electronic Vehicle (HEV) is one of the solutions of high oil price and environment problem. Recently, study of HEV is important for automobile industry. However HEV has a lot of components and there are many cases for assembling, it's impossible to test results from assembling by using real vehicles. To solve this problem, hybrid system simulator is required. The purpose of this study is to develop and optimize of engine module for hybrid system simulator. The commercial 1-D engine simulation program, WAVE is used to get the engine capacity and performance data and 1-D simulation model of base engine is compared with engine experiment results. Using the data, the engine module is developed based on the MATLAB Simulink. There are blocks of base engine, Single-CVVT engine and Dual-CVVT engine. The effect of acceleration and deceleration is applied to each engine block. In addition, the control and processing logics for CIS technology are developed. Finally the simulator operates FTP-72 mode test.

• Journal of Communications and Networks
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• v.18 no.5
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• pp.784-795
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• 2016

In this paper, we investigate the resource allocation problem in time-varying heterogeneous wireless networks (HetNet) with multi-homing user equipments (UE). The stochastic optimization model is employed to maximize the network utility, which is defined as the difference between the HetNet's throughput and the total energy consumption cost. In harmony with the hierarchical architecture of HetNet, the problem of stochastic optimization of resource allocation is decomposed into two subproblems by the Lyapunov optimization theory, associated with the flow control in transport layer and the power allocation in physical (PHY) layer, respectively. For avoiding the signaling overhead, outdated dynamic information, and scalability issues, the distributed resource allocation method is developed for solving the two subproblems based on the primal-dual decomposition theory. After that, the adaptive resource allocation algorithm is developed to accommodate the timevarying wireless network only according to the current network state information, i.e. the queue state information (QSI) at radio access networks (RAN) and the channel state information (CSI) of RANs-UE links. The tradeoff between network utility and delay is derived, where the increase of delay is approximately linear in V and the increase of network utility is at the speed of 1/V with a control parameter V. Extensive simulations are presented to show the effectiveness of our proposed scheme.

• Journal of the Korean Institute of Gas
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• v.21 no.4
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• pp.42-46
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• 2017

As $CO_2$ emission with imprudent using fossil fuel, annual mean temperature of earth is increased in every year. Geothermal energy is inexhaustible energy resource to solve this problem. Heat pump performance and heat exchange efficiency of ground loop are important to distribute widely. Thus, this study are performed to increase heat pump performance and heat exchange efficiency of ground loop with dual expansion valves and spacer. As a results, COP of cooling & heating is obtained improvement up to 11.4% using dual expansion valves, and heat exchange efficiency is increased up to 17.5% using spacer. It will be reduced initial installation cost due to increasing heat pump performance and heat exchange efficiency of ground loop.