• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1C
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• pp.103-112
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• 2010

In this paper, we propose a coarse and fine frequency synchronization method which is suitable for the 3GPP(3rd Generation Partnership Project) LTE(Long Term Evolution) FDD(Frequency Division Duplexing) / TDD(Time Division Duplexing) dual mode system. In general, PSS(Primary Synchronization Signal) correlation based estimation method and CP(Cyclic Prefix) correlation based tracking loop are applied for coarse and fine frequency synchronization in 3GPP LTE OFDMA(Orthogonal Frequency Division Multiple Access) system, respectively. However, the conventional coarse frequency synchronization method has performance degradation caused by fading channel and squaring loss. Also, the conventional fine frequency synchronization method cannot guarantee stable operation in TDD mode because of signal power difference between uplink and downlink subframe. Therefore, in this paper, we propose enhanced coarse and fine frequency synchronization methods which can estimate more accurately in multi-path fading channel and high speed channel environments and has stable operation for TDD frame structure, respectively. By computer simulation, we show that the proposed methods outperform the conventional methods, and verify that the proposed frequency synchronization method can guarantee stable operation in 3GPP LTE FDD/TDD dual mode downlink receiver.

• The Journal of the Acoustical Society of Korea
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• v.37 no.6
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• pp.404-411
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• 2018

This paper proposes a dolphin whistle mimicking underwater communication method using FSK (Frequency Shift Keying) and method to improve BER (Bit Error Rate) performance by using multipath gain combining. The proposed method divides whistle sound into short time intervals and transmits FSK modulated signal that ensures orthogonality of the symbol. Multipath gain can be obtained by using characteristic of mimicked signal frequency that varies with time. To demonstrate the performance of the proposed method, computer simulations and lake experiments were conducted. Computer simulation results show that an additional multipath gain is obtained by multipath. From lake experiments, when symbol length is 20 msec and modulation band is 900 Hz, the proposed FSK method with multipath combining gain obtains BER of 0.002, which is better than CSS (Chirp Spread Spectrum) with BER of 0.185. he proposed based on FSK method has higher imitation degree than the CSS method by analyzing mean cross-correlation value in the time - frequency domain of the imitated signal and actual whistle signal.

• Bulletin of the Korean Chemical Society
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• v.27 no.12
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• pp.2040-2044
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• 2006

Dielectric studies of methyl acrylate with 1-propanol, 1-butanol, 1-heptanol and 1-octanol binary mixtures have been carried out over the frequency range from 10 MHz to 10 GHz at temperatures of 283, 293, 303 and 313 K using Time Domain Reflectometry (TDR) for various concentrations. The Kirkwood correlation factor and excess inverse relaxation time were determined and discussed to yield information on the molecular structure and dynamics of the mixture. The values of the static dielectric constant, relaxation time and the Kirkwood correlation factor decrease with increased concentration of methyl acrylate in alcohol. The Bruggman plot shows a non-linearity of the curves for all the systems studied indicates the heterointeraction which may be due to hydrogen bonding of the OH group of alcohol with C=O of the methyl acrylate. The excess inverse relaxation time values are negative for all the systems at all the temperatures indicates that the solute-solvent interaction hinders the rotation of the dipoles of the system.

• Journal of Communications and Networks
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• v.12 no.6
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• pp.582-591
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• 2010

Probabilistic modeling and analysis of correlation metrics have been receiving considerable interest for a long period of time because they can be used to evaluate the performance of communication receivers, including satellite broadcasting receivers. Although differential correlators have a simple structure and practical importance over channels with severe frequency offsets, closedform expressions for the output distribution of differential correlators do not exist. In this paper, we present detection error probability expressions for frame synchronization using differential correlation, and demonstrate their accuracy over channel parameters of practical interest. The derived formulas are presented in terms of the Marcum Q-function, and do not involve numerical integration, unlike the formulas derived in some previous studies. We first determine the distributions and error probabilities for single-span differential correlation metric, and then extend the result to multispan differential correlation metric with certain approximations. The results can be used for the performance analysis of various detection strategies that utilize the differential correlation structure.

• Wind and Structures
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• v.11 no.2
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• pp.137-152
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• 2008

This paper discusses engineering aspects of the rear-flank downdraft that was recorded near Lubbock, Texas on 4 June 2002, and produced a gust wind speed nearly equal to the design value (50-year return period) for the region. The general characteristics of the storm, and the decomposition of the time histories into deterministic 'running mean' and random turbulence components are discussed. The fluctuating wind speeds generated by the event can be represented as a dominant low-frequency 'running mean' with superimposed random turbulence of higher frequencies. Spectral and correlation characteristics of the residual turbulence are found to be similar to those of high-frequency turbulence in boundary-layer winds. However, the low-frequency components in the running-mean wind speeds are spatially homogeneous, in contrast to the low-frequency turbulence found in synoptic boundary-layer winds. With respect to transmission line design, this results in significantly higher 'span reduction factors'.

• Proceedings of the KOSOMBE Conference
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• v.1992 no.05
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• pp.133-138
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• 1992

Evoked otoacoustic emission (e-OAE) signals are measured from adult and analyzed by computer. Stimulation and detection are repeated and averaged 1000 times for noise cancellation. e-OAE signals are analyzed on frequency domain and time domain. The frequency domain analysis reveals that frequency of stimulus and emission has lineal relationship in 50 dB input sound amplitude. This result altos the cross correlation method to be applied for latency calculation. As the stimulus frequency grows higher, the latency tine is shorter and the gain or emission signal becomes greater. We introduced two mathmatical functions to identify these latecy and gain. These results can be utilized for cochlear modeling.

• Wind and Structures
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• v.12 no.1
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• pp.63-76
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• 2009

The vortex-induced vibration of an ${\sqcap}$-shaped bridge deck sectional model is studied in this paper via the wind tunnel experiment. The vibratory behavior of the model shows that there is a transition of the predominant vibration mode from the vertical to the rotational degree of freedom as the wind speed increases gradually or vice versa as the wind speed decreases gradually. The vertical vibration is, however, much weaker in the latter case than in the former. This is a phenomenon which is difficult to model by existing parametric models for vortex-induced vibrations. In order to characterize the aeroelastic property of the ${\sqcap}$-shaped sectional model, a time domain force identification scheme is proposed to identify the time history of the aeroelastic forces. After the application of the proposed method, the resultant fluid forces are re-sampled in dimensionless time domain so that reduced frequency response function (RFRF) can be obtained to explore the properties of the vortex-induced wind forces in reduced frequency domain. The RFRF model is proven effective to characterize the correlation between the wind forces and bridge deck motions, thus can explain the aeroelastic behavior of the ${\sqcap}$-shaped sectional model.

• Journal of the Korean Home Economics Association
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• v.33 no.3
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• pp.85-99
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• 1995

The major purpose of this research was to investigate the causal relationships among working wives' work-family conflict, socialization of housework, and home management satisfaction. the double ABCX model of family stress and adaptation provided the theoretical framework for this study. the data were recruited from working wives who had more than one pre-school child. The respondents were asked to complete the self-administered questionnaires, and the responses of 536 working wives were used for the final analysis. basically Cronbach's α to the reliability of major variables, frequencies, percentages, means, standard deviation, pearson's correlation coefficients, and LISREL 7 program were performed to test the research model. The results of this study can be summarized as follows : 1. The frequency of work-family conflict was affected by the flexibility of work time and wives' income. 2. The severity of wok-family conflict was directly influenced by the frequency of the conflict, the flexibility of work-time, and wives' education level. 3. The variables influencing the degree of socialization of housework were found to be the frequency and the severity of work-family conflict, wives' education, and the degree of husband's participation in housework. 4. The higher degree of home management satisfaction was associated with the higher level of family member's health status, the greater degree of the flexibility of work-time, and the greater degree of husband's participation in household labor.

• Journal of the Korean Society of Food Science and Nutrition
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• v.27 no.6
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• pp.1285-1296
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• 1998

This study was performed to investigate the food behaviors of college students through a food record method. In this study, one hundred and sixty seven students of Dankook university were chosen(male:77, female:90). We collected data about nutrients intake and food behaviors. Food behaviors included a frequency of both meal and snack, meal time, eating place, person with whom they ate, reason for eating, feeling after eating, and activities during mealtime. The results of the study were summarized as follows. Energy intake per day of male and female were 2201kcal and 1781kcal, respectively. Expect for the protein, vitamin C and phosphate, nutrients were not satisfied with the RDA, especially the intake of vitamin A, Vitamin B2, and calcium was very low. Average eating frequency per day was 5.1 and meal eating frequency per day was 2.6. In addition, male ate more frequently than female did. The interval between breakfast and lunch was 295 minutes, and between lunch and dinner was 373 minutes. The places where they ate the meal and snack were mostly school and restaurant at lunch and dinner, and there was not a significant different between weekday and weekend. On weekdays, the 40~50% of subjects had a breakfast with family, and most students had a lunch or dinner with friends. During weekend, although the percentage of students who had a lunch and dinner with family were increased, a lot of students had a lunch and dinner with friends or alone. In case of reason for meal and snack, the 60~70% of subjects answered that they ate the meal for hunger, and there was not different between weekday and weekend. 60~70% of subjects felt that they eat proper, but the percentage of overeat was increased for dinner. Most students were talking with others while they had a lunch. About 20% of subjects ate only food at both breakfast and dinner and 30% of subjects were watching TV. In correlation between nutrients intake and food behaviors, the higher frequency of eating, the higher carbohydrate intake in male. In case of female, protein intake and dinner time showed the negative correlation, and protein intake and mean intervals of eating had a positive correlation. In case of male, reason for eating affected the nutrient intake, but eating place, after feeling and activity for eating had no relation with nutrients intake. But in case of female, these factors affected nutrient intake. Therefore, food behaviors had an effect on nutrients intake, and the type of effect was different between male and female.

• Journal of Family Resource Management and Policy Review
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• v.19 no.4
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• pp.141-161
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• 2015

The purpose of this study was to explore the differences in time perspective by socio-demographic variables and to investigate the effect of time perspective on time management and life satisfaction for college students. Questionnaires including time perspective, time management, and life satisfaction scales were used for this study. The survey data from 382 college students were analyzed by frequency, percentage, mean, standard deviation, t-test, ANOVA, Duncan test, Pearson's correlation analysis, and stepwise regression. The time perspective, composed of four factors future insensibility and present, past, and future orientation, differed according to the sex, academic grade, and specialty of the college students. The time perspective of the college students and the socioeconomic status of their households were investigated as effective variables on time management and life satisfaction. Based on these results, the implications for research and policy on the time perspective of college students were discussed.