• Journal of KIISE:Databases
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• v.30 no.1
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• pp.27-40
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• 2003

The inverted index widely used in the existing information retrieval field should be extended for XML documents to support containment queries by XML information retrieval systems. In this paper, we consider that there are two methods in storing the inverted index and processing containment queries for XML documents as the previous work suggested: using a RDBMS or using an inverted lift engine. It has two drawbacks to extend the inverted index in the previous work. One is that using a RDBMS is moth worse in the performance than using an inverted list engine. The other is that when containment queries are processed in a RDBMS, there is an increase in the number of a join operation as the path length of a query increases and a join operation always happens between large fables. In this paper. we extend the inverted index in a different way to solve these problems and show the effectiveness of using a RDBMS.

• The Transactions of the Korea Information Processing Society
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• v.4 no.6
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• pp.1433-1442
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• 1997

Algorithm design is needed to optimized bandwidth which satisfy quality of service(QoS) requirements of vary traffic classes for Multimedia service in ATM networks. The diverse flow characteristics e.g., burstiness, bit rate and burst length, have to guarantee the different quality of service(QoS) requirements in Asynchronous Transfer Mode(ATM). The QoS parameter may be measured in terms of cell loss probability and maximum cell dely. In this paper, we consider the ATM networks which the virtual path(vip) concept is implemented by applying the Markov Modulated Deterministic Process method. We develop an efficient algorithm to computer the minimum capacity required to satisfy all the QoS requirements when multiple classes of on-off source are multiplexed on single VP. Using above the result, we propose a simple algorithm to determine the VP combination to achieve the near optimum of total capacity required for satisfying the individual QoS requirements. Numerical results are also presented to demonstrate the performance of the algorithm, when compared to the optimal total capacity required.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.9A
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• pp.728-735
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• 2003

It is a mainly issue that provide mobility smoothly in Mobile IP networks. The IP mobility support being standardized in the IETF utilized tunneling of IP packets from a home agent to foreign agent and utilized reverse tunneling of IP packets from foreign agent to home agent. In this paper, We propose that solve the triangular routing problem in IP mobility and that lessen the messages about IETF routing optimization. Through the Mobile Routing Table on the edge router, agent process the message instead of a end node when handoff occur and that lessen the routing path length by sending directly from FA to to Correspond Node's router. This action lessen the message occurrence frequency and the packet drop. We compare the standard IP, Routing Optimization of Mobile IP, Wu's method and the proposed algorithm. Finally, the simulation results are presented.

• Journal of IKEEE
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• v.20 no.4
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• pp.361-366
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• 2016

This paper presents the ESD protection circuit with improved electrical characteristic and area efficiency. The proposed ESD protection circuit has higher holding voltage and lower trigger voltage characteristics than the 3-Stacking LVTSCR. In addition, it has only two stages and has improved Ron characteristics due to short discharge path of ESD current. We analyzed the electrical characteristics of the proposed ESD protection circuit by TCAD simulator. The proposed ESD protection circuit has a small area of about 35% compared with 3-Stacking LVTSCR, The proposed circuit is designed to have improved latch-up immunity by setting the effective base length of two NPN parasitic bipolar transistors as a variable.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.12
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• pp.1337-1344
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• 2014

The objective of an echo canceller connected to any end of a communication line such as digital subscriber line (DSL) is to compensate the outgoing transmit signal in the receiving path that the hybrid circuit leaks. The echo canceller working in a full duplex environment is an adaptive system driven by the local signal. Conventional echo canceller that implement the least mean square (LMS) algorithm provides a low computational burden but poor convergence properties. The length of the echo canceller will directly affect both the degree of performance and the convergence speed of the adaptation process. To cancel long time-varying echoes, the number of tap coefficients of a conventional echo canceller must be large, which decreases the convergence speed of the adaptive filter. This paper proposes an alternative technique for the echo cancellation in a telecommunication channel. The new technique employs the bi-directional least mean square (LMS) algorithm for adaptively computing the optimal set of the coefficients of the echo canceller, which is composed of weighted combination of both feedforward and feedback algorithms. Finally, Simulation results as well as mathematical analysis demonstrates that the proposed echo canceller has faster convergence speed than the conventional LMS echo canceller with nearly equivalent complexity of computation.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.29 no.1
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• pp.237-243
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• 2005

To design ship channel is one of important factors for planning and developing a port. Bends in channel should be avoided if possible, but the channel should be widened, if channel bend is unavoided, to account widened path of a ship in bend for the safe passage of a ship. In this study, Variable Bumper Area(VBA) model is applied to determine ship channel width in bend and channel-bend geometry. The result of this study shows that the width of a channel in bend may be designed as wide as the width in straight lane provided the angle of deflection is less than 30 degree, should be widened for 60degree deflection based on the length of the largest ship using the channel and the angle of deflection.

• Journal of Navigation and Port Research
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• v.29 no.8 s.104
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• pp.693-699
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• 2005

To design ship channels is one of important factors for planning and developing a port. Bends in channels should be avoided if possible, but the channel should be widened, if channel bend is unavoidable, considering the swept path of a ship for safe passage. In this study, Variable Bumper Area(VBA) model is applied to determine the channel widths in bends. The result of this study shows that the width of the bend may be designed as nearly same size of that in straight channel in case that the angle of deflection is less than 30 degrees, and that of the bend with 60 degrees deflection should be widened based on the length of the largest ship using the channel and the angle of deflection.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.10
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• pp.889-895
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• 2002

Wafer level packaging is gain mote momentum as a low cost, high performance solution for RF-MEMS devices. In this work, the flip-chip method was used for the wafer level packaging of RF-MEMS devices on the quartz substrate with low losses. For analyzing the EM (electromagnetic) characteristic of proposed packaging structure, we got the 3D structure simulation using FEM (finite element method). The electric field distribution of CPW and hole feed-through at 3 GHz were concentrated on the hole and the CPW. The reflection loss of the package was totally below 23 dB and the insertion loss that presents the signal transmission characteristic is above 0.06 dB. The 4-inch Pyrex glass was used as a package substrate and it was punched with air-blast with 250${\mu}{\textrm}{m}$ diameter holes. We made the vortical feed-throughs to reduce the electric path length and parasitic parameters. The vias were filled with plating gold. The package substrate was bonded with the silicon substrate with the B-stage epoxy. The loss of the overall package structure was tested with a network analyzer and was within 0.05 dB. This structure can be used for wafer level packaging of not only the RF-MEMS devices but also the MEMS devices.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.11 s.353
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• pp.14-18
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• 2006

Optical interferometer is used for various optical measurement fields in optical metrology and biomedical measurements. In an optical interferometer, optical delay line has to change the optical path length of a reference arm to match with that of a sample in and it's speed was limited by reference arm movement speed. In this paper, we proposed an all-fibered RSODRapid Scanning-speed Optical Delay) without any mechanical movement, and we applied this system to optical interferometer. Experimental setup is consist of pulse laser source (center wavelength 1304nm, pulse width 30ps, repetition rate 10GHz), two phase modulators and dispersive shifted fiber. As experimental results, we obtain the maximum time delay of 11ps at 10MHz repetition rate, and it is easily tuneable the time delay by modulation frequency and modulation voltage.

• Ocean and Polar Research
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• v.27 no.1
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• pp.87-95
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• 2005

The vertical profiles of radiative flux and heating rate at King Sejong Station in West Antarctica were calculated with radiative transfe model by Chou and Suarez (1999) and Chou et al (2001). To run this model, the profiles of temperature, mixing ratios of water vapor and ozone at King Sejng Station were derived from ECMWF Reanalysis data. The surface temperature and albedo were also derived from NCEP/NCAR Reanalysis and CERES data. The radiative flux strongly depends on the cloud optical path length that was calculated using the measured W-h data and model by Chou and Lee(1996). Durins the period of $2000{\sim}2001$ (12 and 18 UTC), the correlation coefficient between calculated and measured downward solar fluxes at surface was 0.90 and the coefficient for downward longwave flux was 0.61. The calculated net heating rates of surface layer decreased during the same period, the trend of which was in accordance with the decrease of measured temperature.