• Journal of IKEEE
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• v.3 no.1 s.4
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• pp.141-149
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• 1999

If signal time duration of MC-CDMA method which has studied for next-generation high-speed data transmission is not sufficiently large compared to delay spread of channel, the performance is degraded by generation of intersymbol interference. In this paper, this problem will solve through serial to parallel convertor and make large sufficiently time duration of signal compared to delay spread of channel and rise variable spectral efficiency through the number of serial to parallel convertor subchannel we will add to parallel frequency diversity block for improve the performance in mobile Communication. Spectral efficiency of the proposed system is counted and compared to spectral efficiency of MC-CDMA and investigated through computer simulations by using multipath Rayleigh fading channel.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.9A
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• pp.1306-1312
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• 2000

The quality loss of a X-band transmitter has been derived by means of MC simulation. The transmitter as a payload of LEO(Low Earth Orbit) satellite is capable of the down transmission the image data of hundreds Mbps generated from the Electro-Optical Instrument in real time. The parameters such as data asymmetry amplitude unbalance,phase unbalance, wave shaping and channel interference are included in the quality loss simulation Assuming that normally distributed gaussian noise is simply added to the channel, the quality loss of 0.7 dB has been obtained through this simulation based on a 95% confidence interval. The obtained quality loss can be applied to the link budgets as an additional loss item.

• Journal of the Korean Society of Radiology
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• v.14 no.4
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• pp.367-373
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• 2020

Most of the spatial scattered dose caused by the scattered rays generated by the collision between the object and X-rays is relatively easily absorbed by the human body as electromagnetic waves in the low energy region, thereby increasing the degree of radiation exposure. Such spatial scattering dose is also used as an indicator of the degree of radiation exposure of radiation workers and patients, and there is a need for a method to reduce exposure by reducing the spatial scattered dose that occurs indirectly. Therefore, in this study, a lead-free radiation shielding sheet was proposed as a way to reduce the spatial scattering dose, and a Monte Carlo (MC) simulation was performed based on a chest X-ray examination. The absorbed dose was calculated and the measured value and the shielding rate were compared and evaluated.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10c
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• pp.445-447
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• 2001

휴대폰의 사용이 급증하고 스마트폰, PDA와 칼은 우선 단말기 등의 개발이 점차적으로 확대됨에 딸라 이런 휴대용 단말기를 이용하여 인터넷 환경이 아닌 무선 네트웍을 이용하여 데이터 통신을 하는 일이 급속도로 증가 되고 있다. 이런 환경에서 우선 단말기에서 캐쉬를 사용한다고 하면 아직은 적은 메모리와 스토리지 용량을 가진 무선 단말기에서의 데이터 통신을 좀 더 효과적으로 이용할 수 있을 것이다. 특히 본 논문에서는 모바일 클라이언트(MC) 내의 캐쉬 된 데이터가 무효화(invalidation)될 때 서버에서 보내야 하는 무효성 보고 패킷( IR )의 발생과 관련하여 그 패킷 수를 줄여서 대역폭이 낮은 무선 환경에 적합한 알고리즘을 논의한다. MSS(Mobile Switching Station)을 이용한 계층적 캐쉬 알고리즘을 제시하며 데이터의 수정 주기를 이용한 AVI_based 알고리즘을 제시한다. MSS는 MC의 캐쉬의 내용을 알고 있는 state server의 역할을 하게 된다. MC는 캐쉬의 데이터의 avi가 이전보다 짧아졌다는 IR을 받거나 현재 시간과 avi값에 의해 그 데이터가 무효하다는 것을 판단한다. 본 논문의 마지막은 제시된 알고리즘의 시뮬레이션 설계를 통해 AVI 값의 주기성에 따른 성능 평가를 보여준다.

• Journal of Digital Convergence
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• v.12 no.12
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• pp.329-335
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• 2014

In this paper, to improve the performance of PB/MC-CDMA system, we have researched about the decision feedback channel estimation method using the pilot symbol with data symbol. The PB/MC-CDMA system is able to obtain the improved BER by frequency diversity gain and frequency domain equalizer in the frequency selective fading channel. However, when it is not the estimating of channel exactly, it is degrading the performance of BER in the system for occurred the interference among users. To improve the performane system in the multi-user environment the proposed system is using the decision feedback to estimate channel using the channel estimated value of the first stage and second stage. The proposed system is evaluated by computer simulation. The proposed system is not only able to improve the performance of BER by decreasing the interference to each user, but also the proposed system is possible to reduce number of pilot symbol to estimate the channel. Therefore, it confirmed the proposed system improves the performance than the conventional system.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1432-1433
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• 2007

반도체 제조공정에서 널리 쓰이고 있는 플라즈마 에칭프로세스는 기판의 물질을 선택적으로 제거할 때 사용하는 방법이다. 컴퓨터 시뮬레이션을 이용하여 플라즈마 에칭공정을 예측하기 위한 많은 노력이 행하여져 왔다. 그러나 많은 연구에서 플라즈마와 쉬스영역을 따로 모델링하거나 PIC-MC 방법을 이용하였다. 본 논문에서는 반도체 에칭 공정에 사용되는 플라즈마와 플라즈마 쉬스를 상용 코드인 Multiphysics를 사용하여 동시에 시뮬레이션하고 실험결과와의 일치성을 보이고자 한다.

• Proceedings of the Korea Society for Simulation Conference
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• 1992.10a
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• pp.1-1
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• 1992

This paper presents a user-oriented port expansion simulation model that determines the future economic port capacity to meet the projected demand. The model consists of two parts; a physical impact simulation, and an economic impact simulation. The first part of the model simulates the effects caused by the port capacity expansion. The second part evaluates the port economics due to changes in the port capacity. The model was validated by applying it to the actual port expansion followed at the Port of Mobile, Alabama. A case study is then presented to demonstrate the capacity of the model with a coal handling port, the McDuffie Terminals at the Port of Mobile.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.3
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• pp.197-204
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• 2021

If a failure or an abnormal maneuver occurs during the flight test of a missile, the missile is deliberately self-destructed so as not to continue the flight. At this time, debris are produced and it is important to estimate the impact area in real-time whether it is out of the safety area. In this paper, we propose a method to estimate the debris dispersion area and falling time in real-time using a Fully-Connected Neural Network (FCNN). We applied the Unscented Transform (UT) to generate a large amount of training data. UT parameters were selected by comparing with Monte-Carlo (MC) simulation to secure reliability. Also, we analyzed the performance of the proposed method by comparing the estimation result of MC.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.1
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• pp.1-11
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• 2000

We propose a predistorter to compensate for nolinear distortion induced by a high power amplifier employed in multi carrier-code division multiple access (MC-CDMA) systems. The proposed scheme rests upon the fixed point iteration (FPI) associated with the contraction mapping theorem. Unlike the predistorter based on the FPI already presented by the authors in other literatures which operates on complex-valued modulation signals, the proposed predistorter in this paper deals with real-valued FPI on modulation signal amplitudes, resulting in less complexity. Simulation results on a BPSK-modulated, 64-subcarrier synchronous MC-CDMA baseband system with a traveling wave tube amplifier in the transmitter, indicate that the proposed predistorter achieves significant improvement in terms of bit error rate and total degradation over those without the predistorter. Moreover, the proposed predistorter outperforms the complex-valued counterpart, in particular, for small output back-off levels.

• Journal of Internet Computing and Services
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• v.25 no.2
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• pp.93-99
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• 2024

In this paper, we derive the Partial Differential Bond Price Equation (PDBPE) by using Ito's Lemma to determine the pricing of bond on term-structure of interest rate (TSIR) model with jump. From PDBPE, the Maclaurin series (MS) and the moment-generating function (MGF) for the exponential function are used to obtain a numerical solution (NS) of the bond prices. And an algorithm for determining bond prices using Monte Carlo Simulation (MCS) techniques is proposed, and the pricing of bond is determined through the simulation process. Comparing the results of the implementation of the above two pricing methods, the relative error (RE) is obtained, which means the ratio of NS and MCS. From the results, we can confirm that the RE is less than around 2.2%, which means that the pricing of bond can be predicted very accurately using the proposed algorithms as well as numerical analysis. Moreover, it was confirmed that the bond price obtained using the MS has a relatively smaller error than the pricing of bond obtained by using the MGF.