• Journal of Korean Association for Spatial Structures
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• v.17 no.1
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• pp.77-84
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• 2017

Vortex-induced vibration and instability vibration of tall buildings are very important fluid-structure interaction phenomenon, and many fundamental questions concerning the influence of body movement on the unsteady aerodynamic force remain unanswered. For tall buildings, there are two experimental methods to investigate the characteristics of unsteady aerodynamic forces, one is forced vibration method and the other is free vibration method. In the present paper, a free vibration method was used to investigate the unsteady aerodynamic force on tall building whose aspect ratio is 9 under boundary layer simulating city area. Wind pressures on surfaces and tip displacements were measured simultaneously, and the characteristics of tip displacements and generalized forces were discussed. It was found that variation of across-wind displacements showed different trend between the case when wind speed increases and wind speed decreases, and the fluctuating generalize forces in across-wind direction of vibrating model are larger than that of static model near the resonant wind speed and approach to the static value. And for higher wind speed range, there were two peaks in across-wind power spectra of generalize forces of vibrating model, which means that two frequency components are predominant in unsteady aerodynamic forces.

• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1692-1696
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• 2018

Ferroelectric $BaTiO_3$/poly(vinylidene fluoride) (PVDF) nanocomposite films were successfully prepared by mixing $BaTiO_3$ nano-particles into PVDF solution dissolved in dimethylformamide under ultrasonification. The mixture was casted onto glass petri dish and then annealed at $100^{\circ}C$ for 12 h in vacuum dry oven. Crystal structure and surface morphology of the samples were analyzed by using an X-ray diffraction analysis and a field emission-scanning electron microscope, respectively. The relative dielectric permittivity and loss tangent were determined in the frequency range of 50 Hz to 1 MHz. For the $BaTiO_3/PVDF$ nanocomposites, the entire diffraction peaks match those indicated by standard $BaTiO_3$ perovskite structure. The FE-SEM image reveals the homogeneity of the $BaTiO_3$ nanopowder distribution and also predominant 0-3 connectivity. All results show that the dielectric properties of the nanocomposite films are desirable and the fabrication technique for preparing the $BaTiO_3/PVDF$ nanocomposites has a potential in the electronic applications.

• The Journal of Engineering Geology
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• v.1 no.1
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• pp.109-120
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• 1991

Applications of microtremor to geological engineering are widely reviewed and observed microtremors are processed to show evidences of close relationship between the predominant periods of microtremor and underground structure. The ground vibrates continuously at all times and the elastic vibration is called microtremor (0.5-20Hz) or microseisms (0.01-0.1Hz) according to their frequency range. The vibration is believed to have propagative nature like those of the dispersive surface waves or multireflected shear waves. Microtremors were recorded at selected thress places of which subsoil structures are well distinguished in the Kyongsang Sedimentary Basin. It is found that the underground structures estimated from microtremor analysis coincide well with the known structures. The microtremor analysis of the long period range can be an inexpensive and effective tool in geological engineering for the evaluation of the underground structure, site-specific reponse spectrum, and seismic microzonations.

• KIISE Transactions on Computing Practices
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• v.21 no.11
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• pp.713-720
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• 2015

As computing and network technologies are further developed, communication equipment continues to become smaller, and as a result, mobility is now a predominant feature of current technology. Therefore, demand for speech recognition systems in mobile environments is rapidly increasing. This paper proposes a novel method to recognize the Korean vowel 'ㅐ' as a part of a phoneme-based Korean speech recognition system. The proposed method works by analyzing a sequence of patterns in the time domain instead of the frequency domain, and consequently, its use can markedly reduce computational costs. Three algorithms are presented to detect typical sequence patterns of 'ㅐ', and these are combined to produce the final decision. The results of the experiment show that the proposed method has an accuracy of 89.1% in recognizing the vowel 'ㅐ'.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.6
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• pp.959-964
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• 2001

An experimental investigation on the near-field electromagnetic loss of thin copper layers has been presented using microfabricated microwave transceivers for applications to multi-chip microsystems. Copper layers in the thickness range of 0.2$\mu$m∼200$\mu$m have been electroplated on the Pyrex glass substrates. Microwave transceivers have been fabricated using the 3.5mm$\times$3.5mm nickel microloop antennas, electroformed on the silicon substrates. Electromagnetic radiation loss of the copper layers placed between the microloop transceivers has been measured as 10dB∼40dB for the wave frequency range of 100MHz∼1GHz. The 0.2$\mu$m-thick copper layer provides a shield loss of 20dB at the frequencies higher than 300MHz, whereas showing a predominant decreases of shield loss to 10dB at lower frequencies. No substantial increase of the shield effectiveness has been found for the copper shield layers thicker that 2 $\mu$m.

• Food Science and Biotechnology
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• v.17 no.4
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• pp.780-786
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• 2008

Effect of acetylated starches (acetylated rice starch and acetylated tapioca starch) on rheological properties of hot pepper-soybean paste (HPSP) at different mixing ratios of rice flour (RF) and acetylated starch (AS) (10/0, 9/1, 8/2, and 7/3) was evaluated in steady and dynamic shear. All HPSP samples at $25^{\circ}C$ exhibited shear-thinning (n=0.31-0.36) and thixotropic behavior with high yield stresses and their steady flow curves were well described by power law and Casson models. The presence of AS resulted in the decrease in consistency index (K), apparent viscosity (${\eta}_{a,100}$), and yield stress (${\sigma}_{oc}$), and their predominant decreases were noticed at higher ratio of RF to AS (7/3 ratio). Arrhenius temperature relationship represents variation with temperature in the range of $5-35^{\circ}C$ with the high determination coefficients ($R^2=0.97-0.99$). Dynamic moduli (G', G", and ${\eta}^*$) values of HPSP samples mixed with AS were lower than those of HPSP with no added AS within the experimental range of frequency (0.63-62.8 rad/sec). Steady and dynamic shear rheological properties of HPSP samples seem to be greatly influenced by the presence of acetylated starch.

• Structural Monitoring and Maintenance
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• v.6 no.2
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• pp.125-145
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• 2019

Bridge scour is one of the predominant causes of bridge failure. Current climate deterioration leads to increase of flooding frequency and severity and thus poses a higher risk of bridge scour failure than before. Recent studies have explored extensively the vibration-based scour monitoring technique by analyzing the structural modal properties before and after damage. However, the state-of-art of this area lacks a systematic approach with sufficient robustness and credibility for practical decision making. This paper attempts to develop a data-driven methodology for bridge scour monitoring using support vector machines. This study extracts features from the bridge dynamic responses based on a generic sensitivity study on the bridge's modal properties and selects the features that are significantly contributive to bridge scour detection. Results indicate that the proposed data-driven method can quantify the bridge scour damage with satisfactory accuracy for most cases. This paper provides an alternative methodology for bridge scour evaluation using the machine learning method. It has the potential to be practically applied for bridge safety assessment in case that scour happens.

• Journal of Fashion Business
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• v.24 no.6
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• pp.80-88
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• 2020

This study, by analyzing previous studies, aimed to understand how 3D printing technology is applied and utilized in the fashion industry and to contribute to encouraging further studies on 3D printing technology in the fashion sector and suggesting proper ways for designing such studies. Firstly, 47 papers were selected from all literature concerning 3D printing technology published in 15 journals of fashion and design since 2013. Afterwards, these papers were analyzed with regard to the frequency, topics or sectors, and purposes or types of studies shown by outcomes. Results were as follows: First, the number of papers on 3D printing technology published in the journals was counted according to the year, which showed that this number increased rapidly after 2015 for about 3 years. Especially in the year 2016, this increase was quite notable. Although a little decrease in this number was found afterwards, a steady increase was highly expected. Out of the 8 journals, Journal of The Korean Society of Fashion Design had the maximum papers. Regarding areas of studies, works on designing and development of products were most common. Finally, regarding the purpose of studies, those suggesting or presenting apparel were predominant. Product items included clothes, shoes, and caps. Studies on caps mostly covered designing the products. Studies on clothes aimed at designing, characteristics of construction, and case study. However, there were very few works on 3D printing technology as an alternative material or composition of clothing.

• Journal of the Korean Society of Food Culture
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• v.38 no.1
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• pp.61-72
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• 2023

In this study, we identified the differences in food content watching habits and nutrition quotient in adolescent (NQ-A). A total number of 811 subjects were surveyed to establish their general characteristics, food content watching habits, and NQ-A using a self-administered questionnaire. In addition, the mediating effect of watching motivation between the type of food content watched and the NQ-A score was determined. The classification by the type of the food content mainly watched showed that 405 participants (49.9%) watched the Mukbang content, 244 (30.1%) the Cookbang content, and 162 (20.0%) another contents. Among the content watching motives in the Cookbang content group, information acquisition and enjoyment were predominant, whereas emotional satisfaction had the lowest frequency. Compared to the Mukbang content group, when the Cookbang content group mediated information acquisition motivation, the scores of the total, diversity, balance, and practice of NQ-A score areas increased. Compared to the Mukbang content group, the score in the moderation area decreased when the Cookbang content group mediated enjoyment motivation. If food content with accurate information and interesting content are produced and used for adolescent nutrition education, the education will be highly effective.

• Journal of the Korean Institute of Rural Architecture
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• v.26 no.1
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• pp.11-20
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• 2024

Due to the decrease in the school-age population and the overall population, school closures will continue to occur. Currently, most school closures are happening in rural areas, where geographical conditions often result in relatively poor educational, welfare, and cultural facilities compared to urban areas. Additionally, the proportion of elderly populations and migrant women is continuously increasing. In order to effectively utilize closed schools in the future, various efficient utilization methods that align with the social context of the respective regions will be necessary. The purpose of this study is to examine the status of closed school and utilization types in selected rural and island areas of similar sizes through field surveys and literature reviews. By comparing and analyzing these findings, we have identified the predominant utilization types in rural and island areas and assessed the current situation where utilization is lacking. Based on the results, we aim to provide fundamental data for improving and enhancing the utilization of school closures in the face of the ongoing decline in the school-age population.