• Journal of Aerospace System Engineering
• /
• v.18 no.3
• /
• pp.17-26
• /
• 2024

Aircraft engines are exposed to high temperatures, high pressures, and stress caused by the rotation of the turbine shaft during flight. These loads can result in microcracks both on the inside and outside surfaces of the structure. Consequently, this can lead to structural defects and negatively impact the lifespan of the parts. To proactively prevent these defects, a finite element analysis is carried out to identify cracks. However, this process is time-consuming and requires significant effort due to the repetitive nature of crack modeling. This study aims to develop a crack modeling method based on the finite element model. To achieve this, the Constrained Delaunay Triangulation (CDT) technique is employed to triangulate the space while considering limitations on point connections. The effectiveness of this method is validated by comparing stress intensity factors for semi-elliptical cracks in plates and cylindrical vessels. This approach proves to be a valuable tool for crack analysis studies.

• Journal of Preventive Medicine and Public Health
• /
• v.57 no.5
• /
• pp.480-489
• /
• 2024

Objectives: Excess deaths, an indicator that compares total mortality rates before and during a pandemic, offer a comprehensive view of the pandemic's impact. However, discrepancies may arise from variations in estimating expected deaths. This study aims to compare excess deaths in Korea during the coronavirus disease 2019 pandemic using 3 methods and to analyze patterns using the most appropriate method. Methods: Expected deaths from 2020 to 2022 were estimated using mortality data from 2015-2019 as reference years. This estimation employed 3 approaches: (1) simple average, (2) age-adjusted average, and (3) age-adjusted linear regression. Excess deaths by age, gender, and cause of death were also presented. Results: The number of excess deaths varied depending on the estimation method used, reaching its highest point with the simple average and its lowest with the age-adjusted average. Age-adjusted linear regression, which accounts for both the aging population and declining mortality rates, was considered most appropriate. Using this model, excess deaths were estimated at 0.3% for 2020, 4.0% for 2021, and 20.7% for 2022. Excess deaths surged among individuals in their 20s throughout the pandemic, largely attributed to a rise in self-harm and suicide. Additionally, the results indicated sharp increases in deaths associated with "endocrine, nutritional, and metabolic diseases" and "symptoms, signs, and abnormal clinical and laboratory findings, not elsewhere classified." Conclusions: Substantial variations in excess deaths were evident based on estimation method, with a notable increase in 2022. The heightened excess deaths among young adults and specific causes underscore key considerations for future pandemic responses.

• Korean Journal of Environment and Ecology
• /
• v.11 no.1
• /
• pp.18-36
• /
• 1997

This study was conducted to analyze the text relating to the environmental conservation and ecology among the text of the constitution of Korea and collect the domestic laws(40 statutes, 1 guide, 1 leading case) and the foreign laws(1 constitution, 34 statutes, 2 ordinances, 3 leading cases). To make the text of the collected domestic and foreign laws a comparative analysis of the conceptual principle, plan establishment and project operation, types, policy and allied projects, rights and duties, allowed and restricted acts, environmental impact assessment and administration procedure and system of the environmental conservation and ecology by items, it was considered to the mutual relation with lots of laws which are scattered with the various laws and studied to how to set the many foreign countries on their laws connected with the environmental conservation and ecology from the other department and carry out the advanced environmental works.

• Journal of the Institute of Convergence Signal Processing
• /
• v.9 no.2
• /
• pp.121-128
• /
• 2008

Accurate voice activity detection have a great impact on performance of speech applications including speech recognition, speech coding, and speech communication. In this paper, we propose methods for voice activity detection that can adapt to various car noise situations during driving. Existing voice activity detection used various method such as time energy, frequency energy, zero crossing rate, and spectral entropy that have a weak point of rapid. decline performance in noisy environments. In this paper, the approach is based on existing spectral entropy for VAD that we propose voice activity detection method using MFB(Met-frequency filter banks) spectral entropy, gradient FFT(Fast Fourier Transform) spectral entropy. and gradient MFB spectral entropy. FFT multiplied by Mel-scale is MFB and Mel-scale is non linear scale when human sound perception reflects characteristic of speech. Proposed MFB spectral entropy method clearly improve the ability to discriminate between speech and non-speech for various in noisy car environments that achieves 93.21% accuracy as a result of experiments. Compared to the spectral entropy method, the proposed voice activity detection gives an average improvement in the correct detection rate of more than 3.2%.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.20 no.6
• /
• pp.11-17
• /
• 2016

BTTN and TMETN are representative energetic plasticizers used for various propellants. However these compounds are sensitive relatively. So, in order to develop insensitive energetic plasticizer, this study attempted to synthesize derivative of triazole, 4,5-bis(azidomethyl)-(2-methoxyethyl)-1,2,3- triazole (DAMETR). Also, the prepared compound was characterized by NMR, IR spectroscopy, and physicochemical properties such as glass transition temperature, melting point, decomposition temperature, density, viscosity and impact sensitivity. In addition, the heats of formation (${\Delta}H_f$) and detonation properties (pressure and velocity) of DAMETR were calculated using Gaussian 09 and EXPLO5 programs. Especially, 1-DAMETR(>50 J) was more insensitive than BTTN(1 J) and TMETN(9.2 J).

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.49 no.7
• /
• pp.30-38
• /
• 2012

This paper presents packet detection, frequency offset estimation architecture and performance analysis for OFDM-based wireless personal area network (WPAN) systems. Packet detection structure is used to find the start point of a packet exactly in WPAN system as the correlation value passes the constant threshold value. The applied autocorrelation structure of the algorithm can be implemented simply compared to conventional packet detection algorithms. The proposed frequency offset estimation architecture is designed for phase rotation process structure, internal bit reduction to reduce hardware size and the frequency offset adjustment block to reduce look-up table size unlike the conventional structure. If the received signal can be compensated by estimated frequency offset through the correction block, it can reduce the impact on the frequency offset. Through the performance result, the proposed structure has lower hardware complexity and gate count compared to the conventional structure. Thus, the proposed structure for OFDM-based WPAN systems can be applied to the initial synchronization process and high-speed low-power WPAN chips.

• Journal of Korea Game Society
• /
• v.13 no.6
• /
• pp.65-74
• /
• 2013

There are a number of studies about the impact of social games' social network. But because of conflicting results, the game's effect isn't ascertained. In this study, we defined that using social games makes increase the social capital with construal level theory. The survey results on construal level, social capital, game using time, etc, are used for the analysis of the correlation and interact. As a result, growing bridging social capital shows on the people who use high level of construal and more social game time use. This phenomenon did not appear in other online games, so that makes a social games' feature unique characteristic. And we discovered that high level construals is key point for defining the practical use of media.

• Water for future
• /
• v.27 no.3
• /
• pp.35-43
• /
• 1994

Because a failure to provide enough plunge pool depth can create a risk to the structural stability of the psillways or dams, many researchers have proposed experimental formulas for claculating ultimate scour depth under jet issued from spillways and pipe culverts. For the design purposes of a plunge pool, scour potential distribution is important as much as the ultimate scour depth is. In this study scour potential distributions near the jet impinging point on a porous plane which can simulate a real cohesionless movable flat bed has been measured. Experimental results showed that scour potential distributions are geometrically similar to each other provided the angle of jet impact was the same. Statistical analysis of experimental results showed that scour potential distributions for the design purposes of a plunge pool could be expressed by a single equation within a range of this experiment. The proposed formula for the prediction of scour potential distributions agrees well with experimental measurements.

• KIPS Transactions on Computer and Communication Systems
• /
• v.12 no.4
• /
• pp.143-156
• /
• 2023

The domestic threat information sharing system to deal with various security threats in the rapidly changing cyber environment needs to be improved. In this study, to solve these problems and promote the activation of threat information sharing, we derive a research model based on the value-based containment model (VAM) for vital factors in information sharing. After conducting a Ricardian 5-point survey on a total of 204 individuals, the statistical results of the first 151 individuals were analyzed using SPSS and AMOS, and the statistical results of the second 204 individuals were analyzed using R-Studio. As a result, perceivability was found to have a significant impact as a core factor in the activation of cyber threat information sharing (β=0.405, p<0.01), and the hindrance factor was analyzed as innovation resistance (β=-0.152, p<0.01). Microscopically, the obtained results can be applied to factor analysis for activating information sharing of cyber threats by companies in the future, and macroscopically, they can contribute to the foundational development of a national cyber threat response system.

• Journal of dental hygiene science
• /
• v.23 no.4
• /
• pp.271-281
• /
• 2023

Background: This study aims to improve dental hygiene education by investigating the relationship between metacognition, learning flow, and problem-solving abilities in dental hygiene majors. Methods: A survey was conducted on 2nd to 4th-year students from dental hygiene programs, with 132 responses analyzed. Data analysis involved t-tests and ANOVA to examine the differences in metacognition, learning flow, and problem-solving abilities based on the general characteristics. Multiple regression analysis was employed to investigate the factors influencing the dependent variable, which is problem-solving abilities. The collected data were analyzed using SPSS. Results: First, when comparing metacognition, learning flow, and problem-solving abilities based on the general characteristics of the study participants, statistically significant differences were observed in common factors such as major satisfaction, subjective academic performance, GPA (grade point average), and reason for major choice (p<0.05). Second, it was found that there is a significant positive correlation between metacognition, learning flow, and problem-solving abilities in dental hygiene students (r≥0.79, p<0.05). In other words, higher levels of metacognition and learning flow were associated with better problem-solving abilities. Third, factors influencing problem-solving abilities were identified, with both metacognition and learning flow having a statistically significant positive impact. It was also noted that metacognition had a greater influence on problem-solving abilities compared to learning flow (adjusted R²=0.815, p<0.05). Conclusion: To enhance the core competency of problem-solving abilities, it is essential to improve metacognition and learning flow. To enhance metacognition and promote learning flow, strategies such as goal setting, utilizing effective learning methods, boosting self-efficacy, managing the learning environment, choosing activities that foster immersion, stress management, self-assessment and feedback integration, improving focus, and utilization a variety of learning experiences will be necessary.