• The Journal of the Acoustical Society of Korea
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• v.27 no.7
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• pp.342-349
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• 2008

Multipath makes clear message transfer difficult in the underwater communication. To solve this problem, we propose a new method producing proper MFSP (Modulation Frequency Shift Period) which could be obtained by calculating time delay caused by different path from a transmitter to a receiver. At the transmitter end, messages were divided according to the size of the MFSP and transmitted accordingly alternating Frequency. At the receiver end, the received messages were demodulated in order to recover the original message by the adaptive BISMO algorithm which is constructed at the algorithm design stage. Adaptive MFSP and estimated BER (Bit Error Rate) were calculated through simulation test.

• Current Optics and Photonics
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• v.8 no.4
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• pp.345-354
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• 2024

The bit walk-off effect caused by fiber dispersion and carrier reuse in the base station (BS) are two key problems in radio-over-fiber (ROF) systems. In this paper, a novel frequency-octupling ROF system based on the Mach-Zehnder modulator (MZM) is proposed, which can overcome the bit walk-off effect and realize carrier reuse by inserting pilot signals. Theoretical analysis and simulation verification of the system are carried out. Under the condition of a Q factor greater than 6, the optical fiber transmission distance of the upper and lower links is more than 290 km and 80 km, respectively. The influence of the main device parameters of the system on the Q factor is analyzed when they deviate from their designed values. The system designed in this paper can not only effectively overcome the bit walk-off effect, but also solve the problem of downlink performance degradation and the limitation of tunability caused by conventional carrier reuse in ROF. The system can greatly increase the transmission distance and improve the performance of the system and has an important application prospect in ROF.

• Journal of IKEEE
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• v.28 no.3
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• pp.440-444
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• 2024

This paper presents a solution to the frequency coexistence problem between low earth orbit (LEO) satellite networks and other services by utilizing genetic algorithms. Non-terrestrial network (NTN) utilizing LEO satellites have mobility and need to address interference issues that may occur when sharing frequencies with terrestrial services according to propagation rules. In this study, we model the interference scenario based on the NTN operation scenario proposed by 3GPP, and derive the optimal channel allocation scheme for NTNs to protect terrestrial services while satisfying the minimum quality of service (QoS) through genetic algorithm. The simulation results show that the proposed method outperforms the existing fixed assignment method and graph coloring method, and enables efficient frequency sharing.

• Journal of Korean Academy of Nursing
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• v.41 no.2
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• pp.245-255
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• 2011

Purpose: This study was conducted to examine the effects of simulation-based education regarding care in a cardio-pulmonary emergency care as related to knowledge, clinical performance ability, and problem solving process in new nurses. Methods: An equivalent control group pre-post test experimental design was used. Fifty new nurses were recruited, 26 nurses for the experimental group and 24 nurses for the control group. The simulation-based cardio-pulmonary emergency care education included lecture, skill training, team-based practice, and debriefing, and it was implemented with the experimental group for a week in May, 2009. Data were analyzed using frequency, ratio, chi-square, Fisher's exact probability and t-test with the SPSS program. Results: The experimental group who had the simulation-based education showed significantly higher know-ledge (t=5.76, p<.001) and clinical performance ability (t=5.86, p<.001) for cardio-pulmonary emergency care compared with the control group who had traditional education but problem solving process was not included (t=1.11, p=.138). Conclusion: The results indicate that a simulation-based education is an effective teaching method to improve knowledge and clinical performance ability in new nurses learning cardio-pulmonary emergency care. Further study is needed to identify the effect of a simulation-based team discussion on cognitive outcome of clinical nurses such as problem solving skills.

• Journal of Convergence for Information Technology
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• v.8 no.2
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• pp.11-18
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• 2018

The purpose of this study was to analyze the effects of Socio-demographic Characteristics, perceived stress and depression of college students in Daegu and Kyungbuk provinces on problem drinking behavior. The subjects of the study were 295 college students who understood and agreed on the purpose of this study and conducted questionnaires using structured questionnaires. Data were analyzed with frequency, percentage, mean, standard deviation, t-test, ANOVA, Scheffe test, pearson correlation coefficient, and multiple regression analysis. The results showed that depression was the most influential factor in the problem drinking behavior of college students in Daegu and Kyungbuk provinces, followed by gender, academic performance, and residental type. Therefore, it is necessary to develop an intervention program that takes into account the social psychological approach to prevent depression of college students and the characteristics of gender, academic performance, and residental type in order to prevent problem drinking of college students.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.7
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• pp.3412-3432
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• 2019

Recent advances in radio frequency (RF) power transfer provide a promising technology to power sensor nodes. Adoption of mobile chargers to replenish the nodes' energy has recently attracted a lot of attention and the mobility assisted energy replenishment provides predictable and sustained power service. In this paper, we study the joint optimization of mobile charging and data gathering in sensor networks. A wireless multi-functional vehicle (WMV) is employed and periodically moves along specified trajectories, charge the sensors and gather the sensed data via one-hop communication. The objective of this paper is to maximize the uplink throughput by optimally allocating the time for the downlink wireless energy transfer by the WMV and the uplink transmissions of different sensors. We consider two scenarios where the WMV moves in a straight line and around a circle. By time discretization, the optimization problem is formulated as a 0-1 programming problem. We obtain the upper and lower bounds of the problem by converting the original 0-1 programming problem into a linear programming problem and then obtain the optimal solution by using branch and bound algorithm. We further prove that the network throughput is independent of the WMV's velocity under certain conditions. Performance of our proposed algorithm is evaluated through extensive simulations. The results validate the correctness of our proposed theorems and demonstrate that our algorithm outperforms two baseline algorithms in achieved throughput under different settings.

• Journal of Industrial Convergence
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• v.22 no.8
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• pp.105-113
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• 2024

The purpose of the study was to explain the effect of adolescents' problem-solving ability on sociality and to verify the mediating effect of self-esteem in the COVID-19 era. The study utilized the survey data using the web and mobile conducted by the Korea Youth Policy Institute, and selected 1,471 school-age adolescents as the subjects of the survey. For the analysis, the study performed various analysis methods including frequency analysis, descriptive statistics, correlation analysis, and mediating effect analysis of self-esteem using SPSS WIN 25.0 and PROCESS MACRO program. The results are as follows. First, it was shown that adolescents' problem-solving ability had a positive (+) effect on sociality. Second, there was a mediating effect of self-esteem in the relationship between adolescents' problem-solving ability and sociality. Based on these results, the practical engagement and various programs to improve adolescents' self-esteem and sociality were suggested.

• The Korean Journal of Food And Nutrition
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• v.24 no.4
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• pp.481-488
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• 2011

The purpose of this study was to investigate the relations of breakfast skipping and dietary habits according to breakfast intake frequency. Subjects were 5th and 6th graders of elementary school(n=423) in Gyeonggi area. As a result of analyzing the breakfast intake frequency, 'Having everyday' showed the highest 63.4%, followed by '4~6 times' 16.5%, '2~3 times' 13.5% and '0~1 times' 6.6%. As a result of analyzing the relations between mother and child in the breakfast intake frequency, it showed that the more mothers skipped breakfast, the more their children skipped it. For the reason of skipping breakfast, 'To be in time for school' showed the highest percentage. As a result of analyzing the perception of awareness for the importance of nutrition and dietary habit according to the breakfast intake frequency, there was a statistically significant difference in breakfast intake, dietary habits, selection and intake of proper food, disease and health problem according to the breakfast intake frequency. As a result of study, it is necessary that nutrition education should not be limited to children but expanded to their parents in order to increase the efficiency and effectiveness of nutrition education between school and home.

• Journal of Biomedical Engineering Research
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• v.28 no.2
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• pp.258-264
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• 2007

Spatiotemporal changes of brain rhythmic activity at a certain frequency have been usually monitored in real time using scalp potential maps of multi-channel electroencephalography(EEG) or magnetic field maps of magnetoencephalography(MEG). In the present study, we investigate if it is possible to implement a real-time brain activity monitoring system which can monitor spatiotemporal changes of cortical rhythmic activity on a subject's cortical surface, neither on a sensor plane nor on a standard brain model, with a high temporal resolution. In the suggested system, a frequency domain inverse operator is preliminarily constructed, considering the individual subject's anatomical information, noise level, and sensor configurations. Spectral current power at each cortical vertex is then calculated for the Fourier transforms of successive sections of continuous data, when a single frequency or particular frequency band is given. An offline study which perfectly simulated the suggested system demonstrates that cortical rhythmic source changes can be monitored at the cortical level with a maximal delay time of about 200 ms, when 18 channel EEG data are analyzed under Pentium4 3.4GHz environment. Two sets of artifact-free, eye closed, resting EEG data acquired from a dementia patient and a normal male subject were used to show the feasibility of the suggested system. Factors influencing the computational delay are investigated and possible applications of the system are discussed as well.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.6
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• pp.1485-1492
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• 2015

This paper proposes a double frequency method using FTP(Fourier Transform Profilometry) in fringe projection techniques for 3D measurement systems. In fringe projection techniques, fringe pattern images are projected and captured, and then object is measured by analysing phase. PMP(Phase Measuring Profilometry) for analysing phase provides high-resolution and is robust to object's reflection and background intensities. However, the measurement range is narrow due to 2π ambiguity. In order to overcome this problem, a double frequency method is often used. This method can widen the range of measurement while maintaining the high-resolution, but the measurement time is taken about twice due to grab 2 times number of images. The proposed double frequency method using FTP requires an additional image for resolving 2π ambiguity. The proposed method effectively reduces the measurement time while maintaining the same accuracy.