• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.552-554
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• 1995

In long-haul high speed optical communications, the distance between a transmitter and a receiver depends on the amount of light coupled to a single mode optical fiber from the laser diode(LD) as well as the LD characteristic itself. And the transmitter module must have long lifetime. high reliability, and even simple structure. Such points have induced laser welding technique to be a first choice in opto-electronic module packaging because it can provide strong weld joint in a short time with very small coupling loss. In this paper, packaging considerations and characteristics for high speed LD modules are discussed. They include optical path design factors for larger aligning tolerance, and novel laser welding processes for component assembly. For low coupling loss after laser welding processes, the optical path for optimum coupling of a single mode optical fiber into the LD chip was designed with the GRIN lens system providing sufficiently large aligning tolerance both in the radial and axial directions. The measured sensitivity of the LD module was better than -33.7dBm(back to back) at a BER of $10^{-10}$ with a 2.5Gbps NRZ $2^{23}-1$ PRBS.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.12 no.6
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• pp.612-620
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• 1987

In this paper, the optical modem for data link realization is designed with the advantages of optical fiber, large bandwidth, high speed and long haul communication. Modem interface, CCITT V.24 and EIA RS-232C is adopted for the compatibility with existing systems, and biphase coding format is used for digital modulation. And also, modem has serveral loopback test facility in order to diagnose system itself. Optical transmitter and receiver are designed to have the receiving sensitivity of -30dBm at $10^-9$BER in the short wavelength region. Developed system is capable of transmitting data rate at 1200bps up to 57.6Kbps in sync., and at any bps within DC to 200Kbps in async transmission.

• The Korean Journal of Rehabilitation Nursing
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• v.17 no.1
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• pp.10-17
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• 2014

Purpose: The Leeds Sleep Evaluation Questionnaire (LSEQ) translated into Korean was modified to easily apply and reduce respondents' confusion and was evaluated for psychometric properties and discriminant ability. Methods: A total of 960 Korean adults aged 45 years and older participated in this cross-sectional survey. To test reliability, validity and discriminant ability, Cronbach's alpha, correlation analysis, confirmatory factor analysis, simple regression analysis and receiver operating characteristics (ROC) curve analysis were used. Results: Item-total correlations ranged between 62~.85 and Cronbach's alpha was .95. Area under ROC was .86 (95% CI: .83~.90) and the optimal cutoff score was identified as ${\leq}$ 66 (sensitivity, .77; specificity, .84; positive/negative predictive values, .49/.95). Using this cutoff score, the prevalence of insomnia in the study sample was 25.8% and tended to be more common in female and older groups. Conclusion: The data supported the psychometric properties of Korean Modified Leeds Sleep Evaluation Questionnaire (KMLSEQ) as an acceptable sleep measurement. In addition, KMLSEQ is likely to be a useful screening tool for insomnia.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.11
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• pp.1071-1083
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• 1991

In this paper, we describe the design and realization of optical preamplifier with InGaAs APD and GaAs MESFET. Optical preamplifier which is three stage trans-impedance circuit is analyzed in detail and realized in microstrip circuits. With the kmowledge of the InGaAs, GaAs MESFET and BJT, the performance of the optical is predicted by computer simulation and the theoretical predictions are compared with the experimental results. The designed hybrid MIC optical preamplifier exhibits a bandwith of 380MHz and a receiver sensitivity of -40. 6dBm at $1.55{\mu}m$ wavelength when operating at 565Mb/s with BER of $10^{-9}$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4A
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• pp.341-349
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• 2010

In this paper, we studied on the optimization of the output power of Mobile WiMAX (IEEE 802.16) base station considering the technical condition of base station and wireless channel condition. The optimum power of base station can be estimated based on the link budget calculation of downlink and uplink in the Mobile WiMAX communication system. We investigated the optimum output power of base station in the case of 2Tx-2Rx base station with $2{\times}2$ MIMO(multiple input multiple output) technology, 2Tx-4Rx base station with improved receiver sensitivity, and 4Tx-4Rx base station with beamforming technology.

• Korean Journal of Optics and Photonics
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• v.30 no.6
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• pp.230-236
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• 2019

We propose and demonstrate a searching and autoalignment method for indoor optical wireless communication, using a cost-effective retroreflective sheet and a microelectromechanical system (MEMS) mirror. We use an extremum-seeking method for a single axis and beam steering with a MEMS mirror to maintain a line of sight (LOS) with the optical link. This autoalignment method shows a receiver sensitivity of -31.87 dBm for a bit rate of 2.5 Gb/s over a 7 m communication link.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.12 no.3
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• pp.347-353
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• 2005

Purpose: The purpose of this study was to identify whether neck circumference might be correlated with other obesity indices and to determine the neck circumference cutoff level for obesity in female college students. Method: The data were obtained by measuring other anthropometric indices including BMI and neck circumference from 325 female college students in J city, Chungbuk Province. Receiver Operating Characteristic curve(ROC curve) analysis was used to find the optimal neck circumference cutoff level against BMI $25kg/m^2$. Results: The mean BMI was $21.4kg/m^2$, and the prevalence of obesity was 12.6%. Neck circumference was significantly correlated with body weight, BMI, waist circumference, hip circumference, waist to hip ratio, % body fat, triceps skinfold thickness, systolic and diastolic blood pressure. Neck circumference of 31.95cm was the best cutoff level for determining female students with a BMI over $25kg/m^2$, and the characteristic was acceptable with 97.6% sensitivity and 85.6% specificity. Conclusions: Neck circumference was strongly correlated with the other conventional obesity indices. Female college students with neck circumference over 31.95cm require an additional evaluation of obesity.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.1
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• pp.61-72
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• 1997

The implementation of base station transceiver for Wideband CDMA(Code Division Multiple Access) PCS(Personal Communication Service) system using spread spectrum CDMA technology is presented in this paper. The receiver that requires wide dynamic range and high sensitivity and the transmitter that has good spurious emission supression were designed and implemented with 5 MHz RF channel bandwidth. This paper shows the some factors that should be considered and simulated using the RF simulation S/W with commercial and customized components. The implemented transceiver based on the simulation gave good results that satisfied the functional specifications of the transceiver.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.3
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• pp.654-659
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• 2011

We propose a novel method to reduce laser chirp and improve modulation performance in semiconductor laser by using dual-electrode structure. Dual-electrode structure is realized by segmenting a electrode on top of gain medium, as was the case of edge emitting laser diode, into electrically isolated two electrodes. By using the proposed structure, we have experimentally achieved a reduction of laser spectral width of 0.23 nm and an improvement of 2.5-dB receiver sensitivity at an 80-km fiber transmission for 10-Gbps NRZ (non-return-to zero) data stream.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.1
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• pp.16-24
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• 1998

In a high speed long haul fiber optic communication system using modulation, fiber chromatic dispersion and laser chirping can cause serious performance degradations. In this paper, the combined effect of laser chirping and chromatic dispersion on the per- formance of 2.5[Gbps] rate lightwave systems operating at a wavelength of 1550[nm] was investigated. Also we used an optical equalizer to compensate the laser chirping and fiber dispersion, and knew that the receiver sensitivity was improved by about 2 ~ 4[dB].