• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.2
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• pp.233-240
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• 2019

High-altitude ElectroMagnetic Pulse(HEMP) is a high-power electromagnetic pulse caused by nuclear explosions at altitudes above 30 km. This pulse can cause serious damage to the electrical/electronic device. Therefore, there are a lot of studies on the effects of HEMP in the literature. When conducting studies on the effects of HEMP, it is essential to measure the simulated HEMP. Depending on the need for measurement, this paper focuses on the HEMP measurement method. This paper proposes a measurement method using frequency domain compensation to extract the correct waveform and solves the offset problem more efficiently than the conventional methods. The proposed method is verified by experiment using HEMP simulator and measurement system in ADD.

• Advances in nano research
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• v.7 no.5
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• pp.325-335
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• 2019

In the present study, nonlocal strain gradient theory (NSGT) is developed for wave propagation of functionally graded (FG) nanoscale plate in the thermal environment by considering the porosity effect. $Si_3N_4$ as ceramic phase and SUS304 as metal phase are regarded to be constitutive material of FG nanoplate. The porosity effect is taken into account on the basis of the newly extended method which considers coupling influence between Young's modulus and mass density. The motion relation is derived by applying Hamilton's principle. NSGT is implemented in order to account for small size effect. Wave frequency and phase velocity are obtained by solving the problem via an analytical method. The effects of different parameters such as porosity coefficient, gradient index, wave number, scale factor and temperature change on phase velocity and wave frequency of FG porous nanoplate have been examined and been presented in a group of illustrations.

• Journal of Korea Society of Digital Industry and Information Management
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• v.10 no.4
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• pp.133-142
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• 2014

The least mean square(LMS) algorithm has been popular owing to its simplicity, stability, and availability to implement. But it inherently has a problem of slow convergence speed, and the presence of a transfer function in the secondary path following the adaptive controller and the error path has been shown to generally degrade the stability and the performance of the LMS algorithm in applications of acoustical noise control. In general, in order to solve these problems, the filtered-x LMS (FX-LMS) type algorithms can be used and the bi-directional Filtered-x LMS(BFXLMS) algorithm is very attractive among them, which increase the convergence speed and the performance of the controller with nearly equivalent computation complexity. In this paper, a mathematical analysis for the BFXLMS algorithm is presented. In terms of view points of time domain, frequency domain, and stochastic domain, the characteristics and stabilities of algorithm is accurately analyzed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.371.1-371
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• 2002

At lift-off, the jet noise of launch vehicle produces a severe acoustic environment and the loads induced by the acoustic pressure may be damaging to paylaod and equipments. Prediction of the acoustic environment is needed to support the design and test-qualification of components. Currently, such a high frequency problem is usually dealt with by using the SEA, of which the assumptions match reasonably well with the vibro-acoustic condition of system. (omitted)

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.5
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• pp.520-524
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• 2023

An algorithm was developed to detect and block serial arc currents using HPF. The AC series arc problem is that the load current is greater than the fault current and no leakage current occurs. As a solution, an arc detection method utilizing differences in high- frequency amplitudes was developed. HPT was applied to the load current and FFT was applied to eliminate low frequencies. An algorithm has been developed to detect arc waveforms when they exceed a certain value compared to the average of normal waveforms. Using one cycle of data, arc detection is faster and arc accidents are prevented.

• Journal of applied mathematics & informatics
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• v.41 no.6
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• pp.1327-1339
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• 2023

World Wide Web (WWW) use has been increasing recently due to users needing more information. Lately, there has been a growing trend in the document information available to end users through the internet. The web's document search process is essential to find relevant documents for user queries.As the number of general web pages increases, it becomes increasingly challenging for users to find records that are appropriate to their interests. However, using existing Document Information Retrieval (DIR) approaches is time-consuming for large document collections. To alleviate the problem, this novel presents Spatial Clustering Ranking Pattern (SCRP) based Density Ant Colony Information Retrieval (DACIR) for user queries based DIR. The proposed first stage is the Term Frequency Weight (TFW) technique to identify the query weightage-based frequency. Based on the weight score, they are grouped and ranked using the proposed Spatial Clustering Ranking Pattern (SCRP) technique. Finally, based on ranking, select the most relevant information retrieves the document using DACIR algorithm.The proposed method outperforms traditional information retrieval methods regarding the quality of returned objects while performing significantly better in run time.

• Structural Engineering and Mechanics
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• v.88 no.2
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• pp.109-115
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• 2023

In this paper, frequencies of zigzag structure of carbon nanotubes isinvestigated based on Donnell shell theory. These tubes are wrapped with the ring supports in the axial direction. The fundamental frequency curves displayed in article show the dependence of vibrations attributes to zigzag single walled carbon nanotubes. Various zigzag indices are introduced against the variation of length to predict the vibration. Also, the influence of ring supports is sketched with proposed structure for frequency analysis. The frequencies of zigzag tube decreases as the length increases. It is observed that the frequencies decreases with ring support and have higher frequencies without ring. The problem is formulated using Partial Differential Equation. Three expressions of modal deformation displacement functions is used for the elimination of temporal variation to form the solution in the eigen from. For the stability of present study the results are compared with experimentally and numerically in the open text.

• Journal of the Korean Institute of Telematics and Electronics
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• v.11 no.6
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• pp.38-43
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• 1974

A design problem is studied for a nonuniform transmission line (NUTL) section to be inserted between an arbitrary source impedance and an arbitary load impedance for the purpose of impedance matching or providing a minimum input reflection coefficient over a frequency ranee as wide as possible. A special class of NUTL's, yet comprehensive enough to include almost all smoothly varying lines, are considered. Power series expansions of the ABCD parameters of such lines are used in the calculation of the input reflection coefficient. The design problem is formulated as a nonlinear programming problem withnonlinear constraints and is solved by a combined use of the sequential unconstrained minimization technique and tile Fletcher-Powell method. As a result, a line section was obtained which shows a marked improvement over any one hitherto published as a wide-band impedance matching device.

• Research in Community and Public Health Nursing
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• v.10 no.1
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• pp.252-261
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• 1999

The purpose of this study was to investigate the daily stress and stress coping behavior of elementary school children. The subjects for this study were 372 children fourth, fifth and sixth graders from an elementary school in Pusan. We adopted Won - Joo Chung's research instrument (1997) for measuring stress and coping behavior in this study. Statistical techniques such as frequency, percentage, mean, standard deviation, order, and Pearson correlation were used to examine the research questions of this study. The results of this study were as follows: 1. The most common instance of stress to be experienced by all children was the stress from school life, followed by social pressures, individual pressures and family environment. 2. A positive revaluation was the most commonly used stress-coping behavior, followed by behavioral mood conversion, spiritual support, problem-facing behavior, an information search for problem-solving, physical separation for emotional relaxation, avoidance, emotional aggressiveness and emotional expression. 3. Stress-coping behavior had a positive and significant correlation with the stress score(r = .4391, p= .000). In conclusion, the stress from school life was the most common experienced by all children. While independent effort in problem-solving was unsufficient, stress coping behavior had positive results. Therefore, this study verified the necessity of minimizing the stress children experience from school life and of helping them attain desirable stress-coping behaviors.

• Child Health Nursing Research
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• v.26 no.3
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• pp.385-392
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• 2020

Purpose: The number of Korean adolescents engaging in gambling is increasing, especially among out-of-school adolescents. This study aimed to identify patterns of gambling activities and factors related to specific subgroups of out-of-school adolescent gambling activities. Methods: This descriptive study analyzed secondary data from the 2015 Korea Youth Gambling Problem Survey, including 1,200 out-of-school adolescents. Latent class analysis was conducted to identify patterns of gambling activities. The factors related to gambling subgroups were verified with multinomial logistic regression. Results: Three latent classes of gambling activities were identified: rarely gambling (RG), immediate gain gambling (IGG), and broad gambling (BG). These subgroups differed significantly in terms of gender, age at and type of first gambling experience, number and type of gambling activities, gambling frequency, time and money spent on gambling, problem gambling severity, and motivation for gambling. Compared to the RG subgroup, both the IGG and BG subgroups were strongly associated with an older age at the first gambling experience. Conclusion: Out-of-school adolescents who first gambled at an older age and who gambled mainly in order to gain money immediately were at risk of problem gambling. Developing strategies for early screening and referral to professionals is necessary to prevent gambling problems from worsening.