• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.9B
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• pp.1039-1048
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• 2011

Carrier Ethernet, which extend The algorithm based on constructing the mixed topology and performing link stretching, MT/s, has been proposed for designing cost-efficient Carrier Ethernet in optical network with multi-line-rate. However, the MT/s algorithm has high blocking ratio because the wavelength capacity is fully allocated without considering the load balance of network. In this paper, we propose an efficient mixed topology configuration (EMTC) algorithm by modifying MT/s algorithm. In order to reduce blocking ratio, we adapt a threshold for each link to restrict the link utilization so that traffic load can be distributed over whole network. We also apply the EMTC algorithm into optical hybrid switched network to evaluate the availability of our algorithm for different applications. The performance of the EMTC algorithm is compared with that of MT/s algorithm through OPNET simulation. The simulation results show that our algorithm achieve lower blocking ratio than the MT/s algorithm. Moreover, in hybrid switched network, our algorithm performs better than MT/s algorithm in terms of packet loss ratio and end-to-end delay.

• International Journal of High-Rise Buildings
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• v.5 no.3
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• pp.195-203
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• 2016

Shear wall structures have been widely used in high-rise buildings during the past decades, mainly due to their good overall performance, large lateral stiffness, and high load-carrying capacity. However, traditional reinforced concrete wall structures are prone to brittle failure under seismic actions. In order to improve the seismic behavior of traditional shear walls, this paper presents three different metal energy-dissipation shear wall systems, including coupled shear wall with energy-dissipating steel link beams, frame with buckling-restrained steel plate shear wall structure, and coupled shear wall with buckling-restrained steel plate shear wall. Constructional details, experimental studies, and calculation analyses are also introduced in this paper.

• Structural Engineering and Mechanics
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• v.64 no.3
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• pp.301-310
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• 2017

For further development of passive control systems to dissipate larger seismic energy and prevent the structures from earthquake losses, this paper proposes an innovative two-level control system to improve behavior of chevron braced steel frames. Combining two Knee Braces, KB, and a Vertical Link Beam, VLB, in a chevron braced frame, this system can reliably sustain main shock and aftershocks in steel structures. The performance of this two-level system is examined through a finite element analysis and quasi-static cyclic loading test. The cyclic performances of VLB and KBs alone in chevron braced frames are compared with that of the presented two-level control system. The results show appropriate performance of the proposed system in terms of ductility and energy dissipation in two different excitation levels. The maximum load capacity of the presented system is about 30% and 17% higher than those of the chevron braced frames with KB and VLB alone, respectively. In addition, the maximum energy dissipation of the proposed system is about 78% and 150% higher than those of chevron braced frames with VLB and KB respectively under two separate levels of lateral forces caused by different probable seismic excitations. Finally, high performance under different earthquake levels with competitive cost and quick installation work for the control system can be found as main advantages of the presented system.

• Current Optics and Photonics
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• v.1 no.4
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• pp.315-324
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• 2017

In recent years, multicast services such as high-definition television (HDTV), video conferencing, interactive distance learning, and distributed games have increased exponentially, and wavelength-division multiplexing (WDM) networks are considered to be a promising technology due to their support for multicast applications. Multicast survivability in WDM networks has been the focus of extensive attention since a single-link failure in an optical network may result in a massive loss of data. But the improvement of network survivability increases energy consumption due to more resource allocation for protection. In this paper, an energy-efficient multicast algorithm (EEMA) is proposed to reduce energy consumption in WDM networks. Two cost functions are defined based on the link state to determine both working and protection paths for a multicast request in WDM networks. To increase the number of sleeping links, the link cost function of the working path aims to integrate new working path into the links with more working paths. Sleeping links indicate the links in sleep mode, which do not have any working path. To increase bandwidth utilization by sharing spare capacity, the cost function of the protection path is defined to use sleeping fibers for establishing new protection paths. Finally, the performance of the proposed algorithm is evaluated in terms of energy consumption, and also the blocking probability is evaluated under various traffic environments through OPNET. Simulation results show that our algorithm reduces energy consumption while maintaining the quality of service.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.3
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• pp.201-210
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• 2014

In this paper, dc-link voltage control of a grid-connected QZSI is presented. Since the input current of the ZSI is discontinuous, a capacity with relatively large capacitance should be connected to the output of the PV array in order to reduce the current ripple. Due to the presence of the impedance network inductor in series with the PV array, the QZSI can achieve continuous input current flow. Several dc-link voltage control methods are compared and the method for power quality improvement is also presented. The performance of the proposed method is verified through both simulation and experimental results.

• Journal of Information Processing Systems
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• v.13 no.6
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• pp.1544-1553
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• 2017

The network coding mechanism has attracted much attention because of its advantage of enhanced network throughput which is a desirable characteristic especially in a multi-hop wireless network with limited link capacity such as the device-to-device (D2D) communication network of 5G. COPE proposes to use the XOR-based network coding in the two-hop wireless network topology. For multi-hop wireless networks, the Distributed Coding-Aware Routing (DCAR) mechanism was proposed, in which the coding conditions for two flows intersecting at an intermediate node are defined and the routing metric to improve the coding opportunity by preferring those routes with longer queues is designed. Because the routes with longer queues may increase the delay, DCAR is inefficient in delivering real-time multimedia traffic flows. In this paper, we propose a network coding-aware routing protocol for multi-hop wireless networks that enhances DCAR by considering traffic load distribution and link quality. From this, we can achieve higher network throughput and lower end-to-end delay at the same time for the proper delivery of time-sensitive data flow. The Qualnet-based simulation results show that our proposed scheme outperforms DCAR in terms of throughput and delay.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.5
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• pp.376-379
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• 2021

The design and performance of a SiC-MOSFET-based 11-kW bi-directional on-board charger (OBC) for electric vehicles is presented. The OBC consists of a three-phase two-level AC/DC converter and a CLLLC resonant converter. All the power devices are implemented with SiC-MOSFETs to reduce the conduction losses generated in the OBC, and the DC-link voltage is designed to track the level of battery voltage in the forward and reverse powering modes. As a result, the CLLLC resonant converter always runs at the switching frequency near the resonant frequency, resulting in high-efficiency operation at the maximum powering modes. As the DC-link voltage varies according to the battery voltage, the AC/DC converter in the proposed OBC adopts an adaptive DC-link voltage controller. The performance of the proposed 11-kW OBC is verified by a prototype converter with the following specifications: three-phase 60-Hz 380-V input, 11-kW capacity, and battery voltage range of 214-413-V, resulting in the conversion efficiency of over 95.0-% in the forward and reverse powering modes.

• The Transactions of the Korea Information Processing Society
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• v.7 no.10
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• pp.3210-3218
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• 2000

In a IS-95 cellular systm, blocking will occur when the reverse link user interference power reaches a predepermmed level which is set to maintam acceptable signal quality. In this paper, it is assumed that a mobile rdio channel is a shadowing channel and Erlang capacity is calculated for the reverse limk of an imperfect power controlled IS-95 cellular system. the blocking probability is derived using lognornal pproximation and the results according to guassian and lognormal approximation method are compared and analyzed respcctively. Assuming that blocking probability is 1% at the data rate of $R_b$=9.6kbps and $R_b$=14.4kbps, it is shown that Erlang capacity using Iognormal approximation is 13.68 Erlang and 7.08 Erlang and then the approximation erroris occurred about 24.4% and 40.4% inthe garssian approximation, respectively. It is also observed that if the power control becomes periect, the Erlang capacity is increased more 6.99 and 4.21 Erlang than that of the imperfect power control that the power contrl error is 2.5dB, and if voice activity is considered as 10%, the Erlang capacity is increased more 8.21 and 1.25 Erlang than that using non voice activity, respectively.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2430-2434
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• 2003

This paper provides a new approach to analyze the stability of TCP Vegas, which is a kind of feedback-based congestion control algorithm. Whereas the conventional approaches use the approximately linearized model of the TCP Vegas along equilibrium points, this approach uses the exactly characterized dynamic model to get a new stability criterion via a piecewise and delay-dependent Lyapunov-Krasovskii function. Especially, the resulting stability criterion is formulated in terms of linear matrix inequalities (LMIs). Using the new criterion, this paper shows that the current TCP Vegas algorithm is stable in the sufficiently wide region of network delay and link capacity.

• Journal of Korean Institute of Industrial Engineers
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• v.30 no.4
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• pp.277-284
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• 2004

CDMA (Code Division Multiple Access) is a promising air interface technique for digital cellular systems. The soft handoff between base stations is one of many important features of CDMA for the mobile stations crossing the cell boundaries. The service areas of MSC's (Mobile Switching Centers) are defined as the unions of the service areas of the base stations connected to MSC's and are assumed to have hexagonal shapes. An analytical approach to the performance analysis of the link between MSC's for supporting the inter-MSC soft handoff scheme will be developed to obtain the probability that a soft handoff to an adjacent MSC will be blocked due to the shortage of the link capacity. Also, the rate of new connection establishments that are requested by the mobile stations moving to the service area of an MSC according to the inter-MSC soft handoff scheme will be obtained.