• Journal of the Korean Institute of Navigation
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• v.14 no.2
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• pp.1-14
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• 1990

The Radio Navigation System(R. N. S.) has been progressed consistantly with the development of electric-electronic engineering techniques since the R. D. E had been developed in 1910. The R. N. S. mostly depends on either Hyperbolic Navigation System(H. N. S.) or Spherical Navigation System(S. N. S.) in the ocean, and on Rectangular Navigation System (R. N. S.) in the air near the airport or an a combinations of the above systems in both area. Another effective R. N. S may be the Ellipse-Hyperbola Navigation System(E-H N. S.), which is proposed and named such in this paper. The equations calculating GDOP are derived and the GDOP values are calculated in the case of H. N. S., S. N. S, and E-H. N. S., respectively, for the specified case that four transmitting stations are arranged on the apex of a square, Then the GDOP diagrams of above navigation systems are presented for qualitative comparison in this paper. To measure the distances from the receiver to the stations in S. N. S., and/or the sum of distances to two stations in E-H N. S., the time synchronization between the transmitter clocks and the receiver clock is a major premise. The author has proposed the algorithm for getting this synchronmization utilizing the by S. N. S. or E-H N. S while GDOPs of those are relatively good. Even though clock synchronization error is a voidable due to the fix error used, the simulated results shows that the position accuracy of S. N. S. and E-H N. S. by the proposed method is far upgraded compared with that determined by H. N. S. directly, as far as the outer region of transmitter arrangement is concerned.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.7
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• pp.1435-1440
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• 2017

Recently, VR and AR are emerging as an area of interest in ICT. In virtual reality to feel like a real, many people are looking for them because of its charm. However, the motion of the VR image and the moving object are not synchronized exactly, and a problem of feeling nausea is also occurring. The problem should be solved by the application of Attraction in the VR system. In this paper, we propose a module that minimizes delay time by synchronizing movement of VR image and moving object. The proposed module calculates the moving distance using the direction and the acceleration sensor that the user views through the VR device. The module proposed in this paper will pay attention to the fact that the movement of the attraction moves along a fixed path, so that the accurate travel distance can be calculated.

• Journal of KIISE
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• v.44 no.8
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• pp.767-773
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• 2017

In a distributed system environment, such as a cloud database, the tail latency needs to be kept short to ensure uniform quality of service. In this paper, through experiments on a Cassandra database, we show that long tail latency is caused by a lack of memory space because the database cannot receive any request until free space is reclaimed by writing the buffered data to the storage device. We observed that, since the performance of the storage device determines the amount of time required for writing the buffered data, the performance degradation of Solid State Drive (SSD) due to garbage collection results in a longer tail latency. We propose a garbage collection synchronization technique, called SyncGC, that simultaneously performs garbage collection in the java virtual machine and in the garbage collection in SSD concurrently, thus hiding garbage collection overheads in the SSD. Our evaluations on real SSDs show that SyncGC reduces the tail latency of $99.9^{th}$ and, $99.9^{th}-percentile$ by 31% and 36%, respectively.

• The Journal of the Korea Contents Association
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• v.10 no.6
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• pp.213-221
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• 2010

Recently, as the scale of the cultural content business market is being growed, it required that we should introduce the Korean music culture which is unique and competitive cultural contents to the worldwide. This paper proposes a Samulnori Ensemble System (SES), using a touch interface which plays the Korean traditional musical instruments. A SES consists of the Control Device which supports touch functions, the Performance Manager that detects signals from the Control Device and plays a melody, and the Communication Manager making a ensemble among the possible devices. Also, using the Network Time Protocol which is part of Synchronization Manager can be paly different speed communication environments. We utilized multi-touch functions to operate the system. We also implemented multi-touch interface and multi-play with other player for fun and interesting who are not interested Samulnori.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.11
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• pp.2488-2497
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• 1997

In this paper, a computer simulation of the Lornz discrete chaotic system is described. The chotic behavior closely matches the results predicted by numerical simulations. Using the concept of discrete synchronized chaotic systems, the possibility of a secure communication is proved by simulating the Lorenz system in both the transmitter and receiver. In the proposed approach, at first, a chaotic modulating signal is multiplied with the message, and these are transmitted with adding a chaotic modulating signals, and then at the receiver, the chaotic modulating signal is regenerated and divided from the receiver signal. Varying a smapling time interval to calibrate the robustness of the Lorenz discrete synchronized chaotic system as a nonlinear state estimator, we measured the performance of the Lorenz discrete syncrhonized chaotic system by comparing the synchronization error and the error between transmitted signal and received signal.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.1
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• pp.44-57
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• 2013

In this paper, we propose a femtocell searching technique which can prevent a macrocell UE(user equipment) from losing synchronism to its serving macrocell near closed access femtocells in co-channel deployment due to the leakage of femtocell signals by using a CS(Common Signal). The CS, commonly transmitted by femtocells in a macrocell at the same time, enables the macrocell UEs to be kept synchronized with their serving macrocells since the CINR(Carrier to Interference and Noise Ratio) of base stations in macrocell can be kept high even near closed access femtocells. Also, the CS is designed in such a way that a macrocell UE can recognize the existence of femtocell by using the metric CSCINR(Common Signal Carrier to Interference and Ratio) measured with CS. In addition, the proposed femtocell searching technique can reduce the frequency of femtocell searching trial by using the metric on mobility of a macrocell UE defined in this paper, and the reduction of the frequency of handover trial can be also expected as a byproduct.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.6
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• pp.290-297
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• 2014

The synchronization of OFDM receiver is consisted of symbol timing offset(STO) estimation in time domain and carrier frequency offset(CFO) estimation in frequency domain. This paper proposes new algorithm for correcting the integer CFO after we have done correcting the STO and partial CFO. ICFO must be corrected, since the ICFO lead to degrade bit error rate(BER) of demodulation performance. The PN sequence has information which is subcarrier order since the modified PN sequence, length is same subcarrier, is used in this paper and is modulated each subcarrier by each chip. Thus the receiver track phase of PN sequence after FFTin order to find the subcarrier frequency offset. The proposed algorithm is faster and more simple than convenient methode as measuring carrier energy.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.3
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• pp.27-36
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• 2012

With the increase of various user's requirements, lots of interesting applications on the Internet have been emerging recently. However, Internet has many limitations for providing upcoming new services because it was only designed to provide basic connectivity between research networks and simplified forwarding functions at the first time. Internet has many problems in the aspects of routing scalability, mobility, security and QoS, so lots of researches are being actively performed in many countries to solve these problems. In this paper, we implement RED(Random Early Detection) scheduler using NetFPGA platform and local testbed to provide active queue management. Using the implemented RED scheduler, packets are dropped according to the specified drop probability, so Global Synchronization coming from simultaneous TCP segment losses in a congestion condition can be prevented. With the comparison to the Drop-Tail scheme in the basic router, we show TCP performance can be enhanced in the congestion situation using the NetFPGA-based RED scheduler.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.5
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• pp.532-536
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• 2008

In this paper, we propose the method to measure tensions of character motions, using LMA (Laban Movement Analysis). Using tension values, we tan take advantage of them as a standard for synchronization of motion and BGM(Back Ground Music). In LMA, a motion is divided into 4 space-time factors which are called Efforts, and each Effort has two bases opposed to each other. We can analyze the motion by justifying which basis is stronger than the other in each Effort of motion. To measure quantitatively tension values, we propose some equations based on kinematics and dynamics. Then we can measure the tension value by the weighted sum of values calculated from those equations. Each weight can be determined by the optimization process which tries to minimize the difference between the calculated tension value and human's decision. The experimental result shows that the in creasing order of the motion tension value is similar to that of the tension score given by human.

• The Journal of the Korea Contents Association
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• v.10 no.4
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• pp.91-97
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• 2010

Recently, Internet users have an interest about Social Media Service in Web2.0 environment. We suggest the orchestra service as social media service to meet user satisfactions in changed web environment. We accept a concept of the MMMD (Multiple Media Multiple Devices). In other words, Internet users listen to the music not only one device but multiple devices. Each one of multiple devices can play a sound source under earmark instruments for providing users with actual feeling like an orchestra. To meet the purpose, we define 3 steps. First, we separate the sound source based on instrument information. Second, we exact the suitable sound source for play orchestra. In final step, the sound source transmits to each suitable playing device. We named the 3 step for AET process. Beside we suggest synchronization method using rest point in the MIDI file for control sound sources. Using the AET process and synchronization method we provide the orchestra service for meet user's satisfactions to users.