• ETRI Journal
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• v.28 no.1
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• pp.95-98
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• 2006

In this letter, a novel M-ary code-selected direct sequence (DS) ultra-wideband (UWB) communication system is presented. Our purpose is to achieve a high data rate by an M-ary code-selected direct sequence bipolar pulse amplitude modulation (MCSDS-BPAM) scheme. In this system, a particular DS code sequence is selected by the $log_2M$/2 bits from the DS gold code set. This scheme can accomplish both a high data rate without increasing the system bandwidth or changing the pulse shape and improve the BER with an increase of modulation level M even at a lower signal-to-noise ratio (SNR). The receiver signal processing algorithm is given for an MCSDS-BPAM UWB system over an ideal AWGN channel and correlation receivers.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.15 no.1
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• pp.20-26
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• 2015

It is very difficult to design an underwater communication system because of multipath, Doppler effects, noise, and attenuation. These factors lead to errors in the communication performance and maximum propagation distance. In this study, we calculate the distance that can be realized using the direct-sequence code division multiple access (DS-CDMA) technique with direct-sequence spread spectrum (DSSS) in an underwater communication system considering only the attenuation and noise. We also compare the estimated and calculated propagation distances obtained for several different scenarios.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.532-533
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• 2014

본 논문은 LiPB의 SOH (State of Health)를 판별하는 방법중 배터리용량 (Ah) 및 저항 등가모델의 장 단점을 비교한다. 그리고 정확한 SOH 추정을 위해 DCIR (Direct Current Internal Resistance)을 사용한 판별 방법을 제안한다. 정확한 DCIR 값을 추정하기 위하여 EKF (Extended Kalman Filter)를 적용하고, MATLAB 시뮬레이션을 통해 DCIR 값을 확인한다. 또한, 실제 LiPB의 각 SOC (State of Charge) 상태마다 DCIR 값을 측정하고, 추정 값과 비교를 통해 정확도를 판단한다.

• ETRI Journal
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• v.37 no.3
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• pp.460-470
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• 2015

Orthogonal frequency-division multiplexing (OFDM) is one of the most widely used technologies in current wireless communication systems and standards. Cognitive radio (CR) provides a robust solution to the problem of spectrum congestion as it offers opportunistic usage of frequency bands that are not occupied by primary users. Due to the underlying sensing, spectrum shaping, scaling, and interoperable capabilities of OFDM, it has been adapted as a best transmission technology for CR wireless systems. However, the performance of an OFDM-based CR wireless system is affected by the existence of narrowband interference (NBI) from other users. Further, due to carrier frequency offset in NBI sources, NBI energy may spread over all subcarriers of an OFDM signal. In this paper, a fixed Amplify-and-Forward (AF) relay that operates at a frequency band that is different from that of direct mode is introduced to suppress the effect of NBI. Analytical expressions are derived for outage probability in direct, AF-relay, and incremental relaying modes. The outage performance of the proposed AF relay-based CR network is proven to be better than that of direct mode.

• Journal of the Optical Society of Korea
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• v.20 no.5
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• pp.557-562
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• 2016

In this paper, for the first time, the transmission performances of long-haul 100-Gb/s direct detection optical OFDM (DDO-OFDM) and coherent optical OFDM (CO-OFDM) wavelength division multiplexing (WDM) systems are compared by simulation. It provides specific guides for system parameter selection to get a high-performance and cost-effective OFDM WDM system. Specifically, the comparison involves three aspects: launched power is investigated to achieve better system performance; laser linewidth is numerically investigated to choose cost-effective laser; system dispersion tolerances with different laser linewidths are analyzed to further reveal the advantages and disadvantages of these two detecting methods, direct detection and coherent detection, in long-haul OFDM WDM system.

• Journal of Distribution Science
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• v.19 no.1
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• pp.115-124
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• 2021

Purpose: This study examines the effects of several brand variables on customer satisfaction and brand loyalty. Research design, data, and methodology: The survey was conducted on a community with 302 city residents in Greater Jakarta as consumers of lighting products. The constructs were arranged based on several independent variables such as brand experience, brand relationships, and brand trust on customer satisfaction and brand loyalty. Customer satisfaction was positioned as an intervening variable to examine the effects on brand loyalty. Results: The consumer's experience determines the attitude and satisfaction at the next action. Brand experience significantly influences customer satisfaction and brand loyalty. Meanwhile, a brand association related to the benefits of the product concerned so that the relationship also affects customer satisfaction and brand loyalty. However, the brand relationship does not affect brand trust. Consumers do not readily believe without experience. Conclusion: The consumer's experience significantly influences satisfaction and brand loyalty, both direct and indirect. Brand relationships affected customer satisfaction and had a direct effect on brand loyalty. Likewise, brand trust has a direct effect on brand loyalty. The findings' implications emphasize the importance of brand owners to provide positive, memorable experiences to the consumers.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.05a
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• pp.205-209
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• 2000

Modem wireless communication equipments provides various multimedia and aims at the development of low-power, minimum size and weight, and low-cost implimentations. Because of the heterodyne architecture which was invented many decades ago in the wireless communication system using too many components, it was difficult to make it small, compact and On-Chip so it does not proper for future communication. That gives rise a new developing architecture, so called, Direct Conversion. Because The Direct Conversion down-converts the wireless frequency band to baseband directly, it does not need using additive components and has a merit of reduction in power dissipation. We describes the Direct Conversion architecture and DC-Offset, which must be solved, theorectically and predicts system performance enhancement when adopt the AC-Coupling method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.9
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• pp.827-832
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• 2011

Communication is very important in warfare. Dispatch riders were used in ancient warfare, but communication system is used in modern warfare, as the advancement of communication equipments. In order to weaken enemy military strength, communication jamming signal disrupts enemy communication systems. Tone jamming is one of the common communication jamming techniques. Tone jamming is that several tones are placed in the spectrum for neutralizing the enemy's radio communication receivers. In this paper, we develop multitone jamming signal controlled tone number up to 10 tones and tone interval between tones using DDS(Direct Digital Synthesizer) core and FPGA(Field Programmable Gate Arry) of Xilinx Inc. and show the jamming signal output.

• Journal of Family Relations
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• v.21 no.2
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• pp.149-167
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• 2016

Objective: The purpose of this study is to verify the effect of receptivity to multiculturalism on marriage conflict of international marriage couples and mediation effect of communication between two variables. Method: The subjects are 205 individuals of mixed couples who are living in S. Korea. The mediation analysis was based on structural equation modeling followed by bootstrapping with the use of AMOS 22.0. The demographic variables are also controlled in the data analysis. Goodness-of-fit test using RMR, GFI, IFI, TLI, and CFI was conducted. Results: The study results were as follows: first, receptivity to multiculturalism had a direct effect on marital conflict and communication; second, communication had a direct effect on marital conflict; third, communication had a mediation effect between receptivity to multiculturalism and marital conflict. Conclusions: We could verify in this study that receptivity to multiculturalism and communication is the important factor for marital conflicts of mixed couples. More specifically, communication has a critical role for marriage life of mixed couples.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.2
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• pp.1-8
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• 1994

In this paper, a model of trellis-coded M-ary PSK (TCM/M-PSK) for digital land mobile communication is realized. Bit error rate(BER) of TCM/M-PSK is calculated theoretically in time selective fading environment due to Doppler spread in the presence of AWGN. cochannel interference. These analyses are employed the receiver with post detection diversity and the direct sequence to improve the BER performance of TCM-MPSK system. It is shown that the CNR required by the diversity reception and the direct sequece(process gain=20dB) TCM-4PSK system is reduced to about 25 dB.