• 한국통신학회논문지
• /
• 제36권11A호
• /
• pp.924-932
• /
• 2011

본 논문에서는 주파수 도약방식에서는 적용이 어려운 송수신 중첩통신 방식을 DSM형 중계기를 사용하는 위성 데이터링크에 적용하고 항재밍 성능 개선을 위해 잔여 주파수 자원을 주파수 다이버시티에 활용하는 방안을 제안 한다. 시뮬레이션을 통해 제안한 방식에 대한 항재밍 성능과 탐지회피 성능을 분석하였다. 항재밍 성능 분석 결과, 주파수 다이버시티 적용으로 데이터 통신시 18.5dB의 처리이득을 얻을 수 있으며, 500MHz 도약 방식에서 통신단말형태의 재머에 대해 4.8Mbps의 데이터 전송이 가능함을 확인하였다. 또한, 주파수 중첩에 의해 주파수 자원을 최대 2배까지 재사용 가능하며, 데이터 속도를 추정 할 수 있는 D&M 검출기를 대상으로 중첩을 하지 않았을 때 보다 2.5dB LPI 성능이 개선됨을 확인하였다.

• 한국농공학회지
• /
• 제45권5호
• /
• pp.97-109
• /
• 2003

This study is mainly conducted to derive the design drought rainfall by the consecutive duration using probability weighted moments with rainfall in the regional drought frequency analysis. It is anticipated to suggest optimal design drought rainfall of hydraulic structures for the water requirement and drought frequency of occurrence for the safety of water utilization through this study. Preferentially, this study was conducted to derive the optimal regionalization of the precipitation data that can be classified by the climatologically and geographically homogeneous regions all over the regions except Cheju and Ulreung islands in Korea. Five homogeneous regions in view of topographical and climatological aspects were accomplished by K-means clustering method. Using the L-moment ratio diagram and Kolmogorov-Smirnov test, generalized extreme value distribution was confirmed as the best fitting one among applied distributions. At-site and regional parameters of the generalized extreme value distribution were estimated by the method of L-moments. Design drought rainfalls using L-moments following the consecutive duration were derived by the at-site and regional analysis using the observed and simulated data resulted from Monte Carlo techniques. Relative root-mean-square error (RRMSE), relative bias (RBIAS) and relative reduction (RR) in RRMSE for the design drought rainfall derived by at-site and regional analysis in the observed an simulated data were computed and compared. In has shown that the regional frequency analysis procedure can substantially more reduce the RRMSE. RBIAS and RR in RRMSE than those of at-site analysis in the prediction of design drought rainfall. Consequently, optimal design drought rainfalls following the regions and consecutive durations were derived by the regional frequency analysis.

• 한국정보통신학회논문지
• /
• 제7권5호
• /
• pp.879-886
• /
• 2003

주파수 도약 대역확산시스템에서의 광대역 주파수 도약을 위해 주파수 합성기가 널리 이용된다. 따라서 본 논문에서는 효과적인 무선 디지털 데이터 전송 성능을 얻기 위한 FH-FSK 통신에 미치는 주파수 합성기의 영향을 분석하였다. 이를 위해 PLL의 성능을 좌우하는 위상 변화, 스퓨리어스의 발생, PLL의 과도응답 특성에 의해 영향을 받는 주파수 도약율 등 여러 가지 파라미터들에 따른 성능을 분석하였다. 전형적인 PLL을 사용한 주파수 도약 시스템에서는 주파수 도약을 위한 반송파 신호를 국부 발진기에서 만들어낸다. 반송파 간격이 협대역인 협대역 무선 통신 시스템일 경우에는 빠른 주파수 도약을 위한 PLL의 구현이 어렵다. 본 논문에서는 이런 문제점을 해결하기 위해 디지털 주파수 합성기/CPM 변조기를 사용하여 빠른 주파수 도약을 위한 PLL 구현이 가능함을 Matlab tool를 사용한 시뮬레이션 결과를 통해 분석할 수 있었다.

• 전기학회논문지P
• /
• 제59권3호
• /
• pp.253-257
• /
• 2010

The frequency is an important operation parameter for the control, protection, and stability of a power system. The frequency as a key index of power quality can be indicative of system abnormal conditions and disturbances. Due to the sudden change in generation and loads or faults in power system, the frequency is supposed to deviate from its nominal value. It is essential that the frequency must be maintained very close to its nominal frequency. An accurate monitoring of the power frequency is essential to optimal operation and prevention for wide area blackout. As most conventional frequency estimation schemes are based on DFT filter, it has been pointed out that the gain error could cause defects when the frequency is deviated from nominal value. This paper presents an advanced frequency estimation technique using gain compensation to improve the performance of DFT filter based techniques. To evaluate performance of the proposed algorithm, the 765kV T/L system in Korea is simulated by EMTP-RV software. The proposed technique can reduce the gain error caused when the power system frequency deviates from nominal value.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제16권8호
• /
• pp.2704-2719
• /
• 2022

Lately, neo-Chinese style furniture has been frequently noticed by product design professionals for the big part it played in promoting traditional Chinese culture. This article is an attempt to use big data semantic analysis method to provide effective design research method for neo-Chinese furniture design. By using big data mining program TEXTOM for big data collection and analysis, the data obtained from typical websites in a set time period will be sorted and analyzed. On the basis of "neo-Chinese furniture" samples, key data will be compared, classification analysis of overall data, and horizontal analysis of typical data will be performed by the methods of word frequency analysis, connection centrality analysis, and TF-IDF analysis. And we tried to summarize according to the related views and theories of the design. The research results show that the results of data analysis are close to the relevant definitions of design. The core high-frequency vocabulary obtained under data analysis, such as popular, furniture, modern, etc., can provide a reasonable and effective focus of attention for the designs. The result obtained through the systematic sorting and summary of the data can be a reliable guidance in the direction of our design. This research attempted to introduce related big data mining semantic analysis methods into the product design industry, to supply scientific and objective data and channels for studies on design, and to provide a case on the practical application of big data analysis in the industry.

• Journal of Electrical Engineering and Technology
• /
• 제6권4호
• /
• pp.439-446
• /
• 2011

Frequency is an important operating parameter for the protection, control, and stability of a power system. Thus, it must be maintained very close to its nominal frequency. Due to the sudden change in generation and loads or faults in a power system, however, frequency deviates from its nominal value. An accurate monitoring of the power frequency is essential for optimum operation and prevention of wide area blackout. Most conventional frequency estimation schemes are based on the DFT filter. In these schemes, the gain error could cause defects when the frequency deviates from the nominal value. We present an advanced frequency estimation technique using gain compensation to enhance the DFT filter-based technique. The proposed technique can reduce the gain error caused when the frequency deviates from the nominal value. Simulation studies are performed using both the data from EMTP-RV software and the user-defined arbitrary signals to demonstrate the effectiveness of the proposed algorithm. Results show that the proposed algorithm achieves good performance under both steady state tests and dynamic conditions.

• 대한전자공학회논문지TC
• /
• 제44권7호통권361호
• /
• pp.81-87
• /
• 2007

전통적인 셀룰러 시스템에서의 주파수 재사용 방법은 주파수를 분할하고 특정 셀에 위치한 단말들을 특정 주파수 영역에 할당시키는 반면, OFDMA 시스템에서의 주파수 재사용은 스케줄링에 의해서 결정되는 부반송파 할당 문제로 볼 수 있다. 이 논문에서는 주파수 설계에 의해서 인접한 셀들이 배타적인 주파수를 사용하도록 하는 대신, 각 셀이 셀 번호에 따라서 정적으로 결정되는 불규칙적인 패턴을 가지는 주파수 영역을 사용하는 방법을 제안한다. 이 논문에서는 불규칙적인 주파수 할당 패턴을 사용하는 것이 계획적인 주파수 할당을 하는 것에 견줄 정도의 효과적인 간섭 회피와 높은 데이터 전송률을 얻는 것이 가능함을 보인다.

• 한국의류산업학회지
• /
• 제21권1호
• /
• pp.36-45
• /
• 2019

In 2000s, the rapid growth of domestic and foreign fast fashion brands led to an increase in the frequency of shopping for consumers and a significant reduction in the average life span of fashion products. As the kinds and quantity of fashion products owned by individuals increase, the problem of rational clothing management becomes a new concern. The purpose of this study was to investigate the demographic, socio-psychological and purchase behavior factors influencing the frequency of closet cleanup behavior. A total of 278 questionnaires were analyzed. Frequency, exploratory factor analysis, reliability, t-test and regression analysis were used for data analysis using SPSS 22.0. This study results were as follows. First, the frequency of women's closet cleanup behavior was higher than that of men's closet cleanup behavior. Second, the number of brothers and sisters significantly affected the frequency of closet cleanup behavior. Third, the stronger the attachment to fashion products, the higher the frequency of closet cleanup behavior. Fourth, the lower the fashion product retention tendency, the higher the frequency of closet cleanup behavior. Fifth, the higher the frequency of purchasing fashion products, the higher the frequency of closet cleanup behavior. The results of current study provide various implications for educators and marketers who are interested in reasonable management behavior of fashion goods.

• Journal of Positioning, Navigation, and Timing
• /
• 제10권3호
• /
• pp.197-206
• /
• 2021

We compared two typical ensemble time scale algorithms; AT1 and Kalman filter. Four commercial atomic clocks composed of two hydrogen masers and two cesium atomic clocks provided measurement data to the algorithms. The allocation of relative weights to the clocks is important to generate a stable ensemble time. A 30 day-average-weight model, which was obtained from the average Allan variance of each clock, was applied to the AT1 algorithm. For the reduced Kalman filter (Kred) algorithm, we gave the same weights to the two hydrogen masers. We also compared the frequency stabilities of the outcome from the algorithms when the frequency offsets and/or the frequency drift offsets estimated by the algorithms were corrected or not corrected by the KRISS-made primary frequency standard, KRISS-F1. We found that the Kred algorithm is more effective to generate a stable ensemble time scale in the long-term, and the algorithm also generates much enhanced short-term stability when the frequency offset is used for the calculation of the Allan deviation instead of the phase offset.

• 한국의류산업학회지
• /
• 제22권5호
• /
• pp.551-560
• /
• 2020

Due to the nature of fashion design that responds quickly and sensitively to changes, accurate forecasting for upcoming fashion trends is an important factor in the performance of fashion product planning. This study analyzed the major phenomena of fashion trends by introducing text mining and a big data analysis method. The research questions were as follows. What is the key term of the 2010SS~2019FW fashion trend? What are the terms that are highly relevant to the key trend term by year? Which terms relevant to the key trend term has shown high frequency in news articles during the same period? Data were collected through the 2010SS~2019FW Pre-Trend data from the leading trend information company in Korea and 45,038 articles searched by "fashion+material" from the News Big Data System. Frequency, correlation coefficient, coefficient of variation and mapping were performed using R-3.5.1. Results showed that the fashion trend information were reflected in the consumer market. The term with the highest frequency in 2010SS~2019FW fashion trend information was material. In trend information, the terms most relevant to material were comfort, compact, look, casual, blend, functional, cotton, processing, metal and functional by year. In the news article, functional, comfort, sports, leather, casual, eco-friendly, classic, padding, culture, and high-quality showed the high frequency. Functional was the only fashion material term derived every year for 10 years. This study helps expand the scope and methods of fashion design research as well as improves the information analysis and forecasting capabilities of the fashion industry.