• Steel and Composite Structures
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• v.28 no.5
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• pp.589-606
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• 2018

The previous studies reflected the significant effect of neutral-axis position and coupling of in-plane and out-of-plane displacements on behavior of functionally graded (FG) nanobeams. In thin FG beam, this coupling can be eliminated by a proper choice of the reference axis. In shear deformable FG nanobeam, not only this coupling can't be eliminated but also the position of neutral-axis is dependent on through-thickness distribution of shear strain. For the first time, in this paper it is avoided to guess a shear strain shape function and the exact shape function and consequently the exact position of neutral axis for arbitrary gradation of higher order nanobeam are obtained. This paper presents new methodology based on differential transform and collocation methods to solve coupled partial differential equations of motion without any simplifications. Using exact position of neutral axis and higher order beam kinematics as well as satisfying equilibrium equations and traction-free conditions without shear correction factor requirement yields to better results in comparison to the previously published results in literature. The classical rule of mixture and Mori-Tanaka homogenization scheme are considered. The Eringen's nonlocal continuum theory is applied to capture the small scale effects. For the first time, the dependency of exact position of neutral axis on length to thickness ratio is investigated. The effects of small scale, length to thickness ratio, Poisson's ratio, inhomogeneity of materials and various end conditions on vibration and buckling of local and nonlocal FG beams are investigated. Moreover, the effect of axial load on natural frequencies of the first modes is examined. After degeneration of the governing equations, the exact new formulas for homogeneous nanobeams are computed.

• The Korean Journal of Physiology
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• v.1 no.1
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• pp.121-130
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• 1967

Determination of weekly and daily energy expenditure was made on 62 Republic of Korea Army cadets who were selected at random in order to estimate the weekly and daily ealorie expenditure. Basal metabolic rate (B.M.R.), and energy cost of various military and daily activities were measured by indirect calorimetry using open circuit method. Time-motion studies were also carried on using a stop-watch. The total weekly energy expenditure was calculated by summation of data using energy cost per minute, and the time spent on each activity. Determination of daily energy expenditure was deduced from each data of weekly energy expenditure. Food survey was also carried on for a week, and daily calorie intake was determined by a weekly average discounting loss in cooking. All measurements were determined from the Standard Table of Food Composition published by the Ministry of National Defense (1961). Following data were observed. 1. Physical status of cadets are as follows. Please note that the height and weight averages are 1-2cm and 4-5kg respectively over that of the Seoul National University students. First year Height 167.92 cm $(S.D.{\pm}4.09)$ Weight 61.72 kg $(S.D.{\pm}4.53)$ Second year Height 167.89 cm $(S.D.{\pm}3.46)$ Weight 63.01 kg $(S.D.{\pm}4.61)$ Third year Height 168.15 cm $(S.D.{\pm}4.24)$ Weight 43.48 kg $(S.D.{\pm}5.03)$ Fourth year Height 168.10 cm $(S.D.{\pm}3.70)$ Weight 64.02kg $(S.D.{\pm}5.10)$ 2. The B.M.R. of cadets averaged $36.57\;Cal./m^2/hr.(S.D.{\pm}3.63\;Cal./m^2/hr.)$ is almost equal with data on the same ages of civilians and the Japanese, but a lower average of $5.1\;Cal./m^2/hr.$ than that of a common soldier. 3. The energy expenditure during various military activities is close agreement with Consolazio. Passmore and Durnin, and Japanese reports.

• Journal of the Korea Society of Computer and Information
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• v.26 no.2
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• pp.125-132
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• 2021

In this paper, We propose a study on the construction of an environment for collaboration in mixed reality and a method for working with wearable IoT devices. Mixed reality is a mixed form of virtual reality and augmented reality. We can view objects in the real and virtual world at the same time. And unlike VR, MR HMD does not occur the motion sickness. It is using a wireless and attracting attention as a technology to be applied in industrial fields. Myo wearable device is a device that enables arm rotation tracking and hand gesture recognition by using a triaxial sensor, an EMG sensor, and an acceleration sensor. Although various studies related to MR are being progressed, discussions on developing an environment in which multiple people can participate in mixed reality and manipulating virtual objects with their own hands are insufficient. In this paper, We propose a method of constructing an environment where collaboration is possible and an interaction method for smooth interaction in order to apply mixed reality in real industrial fields. As a result, two people could participate in the mixed reality environment at the same time to share a unified object for the object, and created an environment where each person could interact with the Myo wearable interface equipment.

• Journal of Radiation Protection and Research
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• v.47 no.1
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• pp.8-15
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• 2022

Background: We developed a machine vision technology program that tracks patients' real-time breathing and automatically analyzes their breathing patterns. Materials and Methods: To evaluate its potential for clinical application, the image tracking performance and accuracy of the program were analyzed using a respiratory motion phantom. Changes in the stability and regularity of breathing were observed in healthy adult volunteers according to whether the breathing pattern mirrored the breathing guidance. Results and Discussion: Displacement within a few millimeters was observed in real-time with a clear resolution, and the image tracking ability was excellent. This result was consistent even in the sections where breathing patterns changed rapidly. In addition, the respiratory gating method that reflected the individual breathing patterns improved breathing stability and regularity in all volunteers. Conclusion: The findings of this study suggest that this technology can be used to set the appropriate window and the range of internal target volume by reflecting the patient's breathing pattern during radiotherapy planning. However, further studies in clinical populations are required to validate this technology.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.4
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• pp.312-326
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• 2012

This paper considers a fully coupled 3D BEM-FEM analysis for the ship structural hydroelasticity problem in waves. Fluid flows and structural responses are analyzed by using a 3D Rankine panel method and a 3D finite element method, respectively. The two methods are fully coupled in the time domain using a fixed-point iteration scheme, and a relaxation scheme is applied for improve convergence. In order to validate the developed method, numerical tests are carried out for a barge model. The computed natural frequency, motion responses, and time histories of stress are compared with the results of the beam-based hydroelasticity program, WISH-FLEX, which was thoroughly validated in previous studies. This study extends to a real-ship application, particularly the springing analysis for a 6500 TEU containership. Based on this study, it is found that the present method provides reliable solutions to the ship hydroelasticity problems.

• Clinical and Experimental Pediatrics
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• v.60 no.6
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• pp.196-201
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• 2017

Purpose: Myocardial dysfunction and dysrhythmias are inevitable consequences of Duchenne muscular dystrophy. We aimed to evaluate specific trends of electrocardiographic changes that reflect the progress of cardiomyopathy in patients with Duchenne muscular dystrophy. Methods: Fifty electrocardiograms (ECGs) of 30 patients (ages 1 to 27 years) who had not been prescribed medications for heart failure treatment at the time of examination were retrospectively analyzed and compared with 116 ECGs of age-matched healthy 116 controls. Heart rate, leads with fragmented QRS (fQRS), corrected QT, Tpeak-to-Tend, and Tpeak-to-Tend/QT were analyzed. Results: The patients with Duchenne muscular dystrophy failed to show a normal age-related decline in heart rate but showed an increasing trend in the prevalence of fQRS, corrected QT, corrected Tpeakto-Tend, and Tpeak-to-Tend/QT over time. In the ${\leq}10-year-old$ patient group, a significant difference was found only in the prevalence of fQRS between the patients and the controls. The prevalence of fQRS, heart rate, Tpeak-to-Tend/QT, and corrected Tpeak-to-Tend demonstrated significant differences between the patients and the controls in the middle age group (11 to 15 years old). All the indexes were statistically significantly different in the ${\geq}16-year-old$ patient group. Conclusion: The prevalence of lead with fQRS representing regional wall motion abnormalities was higher in the young patients than in the young healthy controls, and this might be one of the first signs of myocardial change in the patients. Markers of depolarization and repolarization abnormalities were gradually prominent in the patients aged >10 years. Further studies are needed to confirm these findings.

• Journal of Korean Society for Quality Management
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• v.51 no.2
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• pp.171-184
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• 2023

Purpose: First, this paper suggests an alternative approach to find optimal portfolio (stocks, bonds and ESG stocks) under the maximizing utility of investors. Second, we include ESG stocks in our optimal portfolio, and compare improvement of welfares in the case with and without ESG stocks in portfolio. Methods: Our main method of analysis follows Brennan et al(2002), designed under the continuous time framework. We assume that the dynamics of stock price follow the Geometric Brownian Motion (GBM) while the short rate have the Vasicek model. For the utility function of investors, we use the Power Utility Function, which commonly used in financial studies. The optimal portfolio and welfares are derived in the partial equilibrium. The parameters are estimated by using Kalman filter and ordinary least square method. Results: During the overall analysis period, the portfolio including ESG, did not show clear welfare improvement. In 2017, it has slightly exceeded this benchmark 1, showing the possibility of improvement, but the ESG stocks we selected have not strongly shown statistically significant welfare improvement results. This paper showed that the factors affecting optimal asset allocation and welfare improvement were different each other. We also found that the proportion of optimal asset allocation was affected by factors such as asset return, volatility, and inverse correlation between stocks and bonds, similar to traditional financial theory. Conclusion: The portfolio with ESG investment did not show significant results in welfare improvement is due to that 1) the KRX ESG Leaders 150 selected in our study is an index based on ESG integrated scores, which are designed to affect stability rather than profitability. And 2) Korea has a short history of ESG investment. During the limited analysis period, the performance of stock-related assets was inferior to bond assets at the time of the interest rate drop.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.45 no.4
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• pp.59-70
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• 2008

In this paper, we proposed image processing technique for automatic real-time fire and smoke detection in tunnel environment. To avoid the large scale of damage of fire occurred in variety environments, it is purposeful to propose many studies to minimize and to discover the incident as fast as possible. But we need new specific algorithm because tunnel environment is quite different and it is difficult to apply previous fire detection algorithm to tunnel environment. Therefore, in this paper, we proposed specific algorithm which can be applied in tunnel environment. To minimize false detection in tunnel we used color and motion information. And it is possible to detect exact position in early stage with detection, test, verification procedures. In addition, by comparing properties of each algorithm throughout experiment, we have proved the validity and efficiency of proposed algorithm.

• Journal of ILASS-Korea
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• v.22 no.4
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• pp.210-217
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• 2017

A gasoline direct injection engine has an intake air temperature can be lowered by the fuel vaporization in the combustion chamber increase the volume efficiency is high compression ratio. Therefore, study for injection rate and characteristics which influence mixture formation in combustion chamber is important. Movement of the injector needle has a direct effect on the injection of the fuel, such as formation of cavitation, the fuel injection rate, etc. Therefore, recent studies on the dynamic characteristics of the injector considering the movement of the needle have been reported, but it takes a lot of time and cost to experimentally confirm the movement of the needle inside the injector. In this study, AMESim, a commercial 1-D code, and Star-CCM+, a 3-D CFD code, were used to predict the dynamic performance of the injector with needle motion. In order to predict the movement of the needle under the high pressure, the result of the surface pressure distribution according to the movement of the needle was derived by using the morphing technique of flow analysis. In addition, we predicted the injection rate of the injector considering the movement of the needle in conjunction with the 1-D code. The injection rate of the injector was measured by the BOSCH's method and the results were similar to those of the simulation results. This method can predict the injection rate and injection characteristics and this result is expected to be used to predict the performance of gasoline direct injection engines with low cost and time in the future.

• Tribology and Lubricants
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• v.40 no.3
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• pp.91-96
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• 2024

Recently, extensive studies have been carried out to enhance various performance aspects such as the durability, lifespan, and hardness by combining diverse materials or developing novel materials. The utilization of superhydrophobic surfaces, particularly in the automotive, textile, and medical device industries, has gained momentum to achieve improved performance and efficiency. Superhydrophobicity refers to a surface state where the contact angle when water droplets fall is above 150°, while the contact angle during sliding motion is smaller than 10°. Superhydrophobic surfaces offer the advantage of water droplets not easily sliding off, maintaining a cleaner state as the droplets leave the surface. Surface modification involves two fundamental steps to achieve superhydrophobicity: surface roughness increase and surface energy reduction. However, existing methods, such as time-consuming processes and toxic organic precursors, still face challenges. In this study, we propose a method for superhydrophobic surface modification using lasers, aiming to create roughness in micro/nanostructures, ensuring durability while improving the production time and ease of fabrication. The mechanical durability of superhydrophobic samples treated with lasers is comparatively evaluated against chemical etching samples. The experimental results demonstrate superior mechanical durability through the laser treatment. Therefore, this research provides an effective and practical approach to superhydrophobic surface modification, highlighting the utility of laser treatment.