• Electronics and Telecommunications Trends
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• v.36 no.3
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• pp.53-64
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• 2021

As the 5G service market is expected to grow rapidly, the development of high-power, high-efficiency power amplifiers for the 5G communication infrastructure is indispensable. Gallium nitride (GaN) is attracting great interest as a key device in power devices and integrated circuits due to its wide bandgap, high carrier concentration, high electron mobility, and high-power saturation characteristics. In this study, we investigate the technology trends of Ka-band GaN radio frequency (RF) power devices and integrated circuits for operation in the millimeter-wave band of recent 5G mobile communication services. We review the characteristics of GaN RF high electron mobility transistor (HEMT) devices to implement power amplifiers operating at frequencies around 28 GHz and compare the technology of foreign companies with the device characteristics currently developed by the Electronics and Telecommunication Research Institute (ETRI). In addition, the characteristics of Ka-band GaN monolithic microwave integrated circuit (MMIC) power amplifiers manufactured using various GaN HEMT device technologies are reviewed by comparing characteristics such as frequency band, output power, and output power density of integrated circuits. In addition, by comparing the performance of the power amplifier developed by ETRI, the current status and future direction of domestic GaN power devices and integrated circuit technology will be discussed.

• The Journal of the Korea Contents Association
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• v.21 no.7
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• pp.134-143
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• 2021

Recently, with the development of mobile devices and social media services, contents recommendation schemes have been studied. They are typically applied to the job curation systems. Most existing university education content recommendation schemes only recommend the most frequently taken subjects based on the student's school and major. Therefore, they do not consider the type or field of employment that each student wants. In this paper, we propose a university educational contents recommendation scheme for job curation services. The proposed scheme extracts companies that a user is interested in by analyzing his/her activities in the job curation system. The proposed scheme selects graduates or mentors based on the reliability and similarity of graduates who have been employed at the companies of interest. The proposed scheme recommends customized subjects, comparative subjects, and autonomous activity lists to users through collaborative filtering.

• Advances in nano research
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• v.12 no.5
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• pp.529-547
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• 2022

Graphene is one of the strongest, stiffest, and lightest nanoscale materials known to date, making it a potentially viable and attractive candidate for developing lightweight structural composites to prevent high-velocity ballistic impact, as commonly encountered in defense and space sectors. In-plane twist in bilayer graphene has recently revealed unprecedented electronic properties like superconductivity, which has now started attracting the attention for other multi-physical properties of such twisted structures. For example, the latest studies show that twisting can enhance the strength and stiffness of graphene by many folds, which in turn creates a strong rationale for their prospective exploitation in high-velocity impact. The present article investigates the ballistic performance of twisted bilayer graphene (tBLG) nanostructures. We have employed molecular dynamics (MD) simulations, augmented further by coupling gaussian process-based machine learning, for the nanoscale characterization of various tBLG structures with varying relative rotation angle (RRA). Spherical diamond impactors (with a diameter of 25Å) are enforced with high initial velocity (V_i) in the range of 1 km/s to 6.5 km/s to observe the ballistic performance of tBLG nanostructures. The specific penetration energy (E_p^*) of the impacted nanostructures and residual velocity (V_r) of the impactor are considered as the quantities of interest, wherein the effect of stochastic system parameters is computationally captured based on an efficient Gaussian process regression (GPR) based Monte Carlo simulation approach. A data-driven sensitivity analysis is carried out to quantify the relative importance of different critical system parameters. As an integral part of this study, we have deterministically investigated the resonant behaviour of graphene nanostructures, wherein the high-velocity impact is used as the initial actuation mechanism. The comprehensive dynamic investigation of bilayer graphene under the ballistic impact, as presented in this paper including the effect of twisting and random disorder for their prospective exploitation, would lead to the development of improved impact-resistant lightweight materials.

• Journal of People, Plants, and Environment
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• v.24 no.6
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• pp.595-608
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• 2021

Background and objective: For effective horticultural education, it is required to develop kits for practice. In this study, we developed a horticultural kit for germination that introduces storytelling, characterization, and assembly, and investigated the educational effects of using it to study its educational differentiation and usefulness. Methods: First, we developed a seed germination kit for learning. It consists of three components: the kit main frame for hydroponics, the activity sheet for storytelling, and the instruction manual. It is made into an acrylic assembly in consideration of the ease of delivery for contactless learning. Second, we developed two programs, each using a germination kit for horticultural education (experimental group) and a general germination kit program (control group). At this time, the class consists of pre-questionnaire, the 1st and 2nd classes, observation log writing (total six times for two weeks), the 3rd class, and post-questionnaire. The experimental group and control group were separately executed. Third, the application results were compared and analyzed before and after class. As a quantification questionnaire, the effects before and after class were compared through t-test with a questionnaire on program satisfaction and attitude change toward plants. The quantitative results were analyzed through observation activity sheets and effects before and after the class were analyzed through t-test with quantification and language coding. Results: The effect of horticulture education using the developed kit was estimated by a quantification questionnaire. Both the program satisfaction and the change in attitude toward plants showed high in the experimental group, and this difference was statistically significant (p < .05). As a result of analyzing the observation paper with a qualitative questionnaire, various cognitive and affective expressions appeared in the experimental group as well as the contents of the observation paper. The number of syllables and various qualitative expressions appeared, and these differences were also statistically significant (p < .05). Conclusion: Compared to general germination activities, it was found that the germination activities using storytelling-based horticultural kits would be effective for contactless classes in the post-COVID-19 era and in increasing the educational effect of horticultural activities.

• Journal of Korea Entertainment Industry Association
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• v.14 no.4
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• pp.145-153
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• 2020

In the rapidly changing era of the fourth industry, big data is being used in various fields. In recent years, the use of big data has been rapidly applied to overall cultural and artistic contents, and among them, the use of big data is essential as a film genre with a lot of capital. This research method is analyzed as the film , which won the Palme d'Or Prize of the 72nd Cannes Film Festival in 2019 and the works and directors' award at the Academy Awards. The analyzed value predicts the film's performance through opinion mining, which gives the value of the change and sensitivity of each data cycle, and extracts the utilization index and topic keywords of SNS such as Facebook and Twitter to reflect the audience's interest. Identify the factors. As such, if model performance and model development can be predicted through model analysis of film performance using big data, the efficiency of the film production process will be maximized while the risk of production cost and the risk of film failure will be minimized.

• The Journal of the Korea Contents Association
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• v.21 no.11
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• pp.145-155
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• 2021

Recently because of development of technology the old cultural properties and damaged artworks are stored as digital information using digital technology and produced related contents as well as moving images or digital contents. The regenerated information and contents through digital technology conveys correct information of ancient art and helps audiences appreciate it, as well as it also stores accurate information and can be used for restoration and preservation of the work. In this study, the range of digital restoration was defined in three directions, and the exhibition of digital content with an ancillary role that can be useful the understanding of the heritage of nature and mankind using digital technology was defined as the range of digital restoration. In addition, the Ojukheon Museum in Kangneung and The Museum of Natural History in New York, which installed various digital displays to analyze and compare the types of digital display exhibitions used for digital restoration of the range, were described as examples. Through this, it was discovered that digital display exhibitions for digital restoration can effectively deliver information and stimulate participation and interest of visitors in the museums, which is able to be a positive way to preserve the heritage of nature and mankind.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.5
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• pp.675-681
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• 2022

Recently, with the development of IoT technology and AI, unmanned and automated in various fields, interest in video processing, which is the basis for automation such as object recognition and object classification, is increasing. Various studies have been conducted on noise removal in the video processing process, which has a significant impact on image quality and system accuracy and reliability, but there is a problem that it is difficult to restore images for areas with high impulse noise density. In this paper proposes a filter algorithm based on partial mask and Lagrange interpolation to restore the damaged area of impulse noise in the image. In the proposed algorithm, the filtering process was switched by comparing the filtering mask with the noise estimate and the purge weight was calculated based on the low frequency component and the high frequency component of the image to restore the image.

• Korean Journal of Organic Agriculture
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• v.30 no.1
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• pp.103-118
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• 2022

Photorhabdus is a bacterial symbiont of entomopathogenic nematodes of the genus Heterorhabditis in the family Heterorhabditidae. Photorhabdus is known to have nematicidal activity in addition to insecticidal activity. P. temperata isolated from Korean indigenous H. megidis Gwangju strain also produced high control efficacy against root-knot nematode Meloidogyne incognita and root-lesion nematode Pratylenchus penetrans. P. temperata has drawn interest as a potential bionematicide for the control of root-knot nematodes thereby. For the registration as an organic agricultural material, the toxicity of P. temperata was assessed by the acute toxicity test in carp (Cyprinus carpio) and acute oral and dermal toxicity tests in Sprague-Dawley rat (Rattus norvegicus) in compliance with the guidelines of the Rural Development Administration (RDA). In the acute toxicity test in fish, neither lethality nor abnormal responses of carp were observed. Body length and weight of carp and changes in DO concentrations and pH values were not significantly different between the treated group and the untreated control. In the acute oral and dermal toxicity tests, clinical signs, abnormal behavior, mortality, and pathological findings were not observed in all the experimental rats. The weight increment of all rats was normal. Acute toxicity results of P. temperata in fish and rats belonged to categories III, IV, and IV of RDA, respectively. Toxicity results of the present study indicated that P. temperata could be a safe and promising bionematicide against root-knot nematodes and root lesion nematode.

• Journal of the Korea Society for Simulation
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• v.31 no.4
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• pp.11-22
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• 2022

Unlike a short-range, a long-range underwater acoustic communication(UWAC) uses low frequency signal and deep sound channel to minimize propagation loss. In this case, even though communication signals are modulated using a covert transmission technique such as spread spectrum, it is hard to conceal the existence of the signals. The unconcealed communication signal can be utilized as active sonar signal by enemy and presence of underwater vehicles may be exposed to the interceptor. Since it is very important to maintain stealthiness for underwater vehicles, the detection probability of friendly underwater vehicles should be considered when interceptor utilizes our long-range UWAC signal. In this paper, we modeled a long-range UWAC environment for analyzing the detection performance of underwater vehicles and proposed the region of interest(ROI) setup method and the measurement of detection performance. By computer simulations, we yielded parameters, analyzed the detection probability and the detection performance in ROI. The analysis results showed that the proposed detection performance analysis method for underwater vehicles could play an important role in the operation of long-range UWAC equipment.

• Land and Housing Review
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• v.13 no.2
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• pp.81-90
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• 2022

This study is based on social needs for green healing spaces assumed to enhance mental health in a city. This study proposes development directions through the analysis of modern social recognition factors for neighborhood gardens. As a research method, web information data was collected using Textom among big data tools. Text Mining was conducted to extract elements and analyze their relationship through keyword analysis, network analysis, and cluster analysis. As a result, first, the healing space and the healing environment were creating an eco-friendly healthy environment in a space close to the neighborhood within the city. Second, neighborhood gardens included projects and activities that involved government, local administration, and citizens by linking facilities as well as living culture and urban environments. These gardens have been reinforced through green welfare and service programs. In conclusion, friendly gardens in the neighborhood for the purpose of public interest, which are beneficial to mental health, are green infrastructures as a healing environment that can produce positive effects.