• Journal of the Korea Institute of Military Science and Technology
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• v.2 no.2
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• pp.110-116
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• 1999

Supersonic flows over an EFP(explosively formed projectile) have been calculated by a high-order conservation law scheme and two-layer $$textsc{k}$-{\varepsilon}$ model on hybrid viscous unstructured mesh. To verify the accuracy and robustness of the developed code, two basic flows about airfoils are computed and results are compared with existing experimental data and computational results. The comparisons confirm the validity of the code and justify our use for such a highly supersonic and viscous flow over a blunt body. Complex flow features of supersonic flows over an EFP are clearly captured and show agreements with the flow visualization. From the interaction of oblique shocks near the surface of flare, flow structures, that were not identified by previous experimental results, are discovered as a result of present computation.

• Kyungpook Mathematical Journal
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• v.56 no.2
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• pp.311-327
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• 2016

In this paper, we propose an error embedded Runge-Kutta method to improve the traditional embedded Runge-Kutta method. The proposed scheme can be applied into most explicit embedded Runge-Kutta methods. At each integration step, the proposed method is comprised of two equations for the solution and the error, respectively. These solution and error are obtained by solving an initial value problem whose solution has the information of the error at each integration step. The constructed algorithm controls both the error and the time step size simultaneously and possesses a good performance in the computational cost compared to the original method. For the assessment of the effectiveness, the van der Pol equation and another one having a difficulty for the global error control are numerically solved. Finally, a two-body Kepler problem is also used to assess the efficiency of the proposed algorithm.

• Journal of Auto-vehicle Safety Association
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• v.14 no.3
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• pp.77-82
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• 2022

The Korea's automobile safety standards consist of standards for automobiles, automated vehicles, two-wheeled vehicles and auto parts, and there are 157 articles. In connection with the safety standards, the implementation rules stipulated for detailed test methods and procedures are composed of the main body, asterisks and annexes, and have a rather complicated structure. In addition, the test items in the asterisk are specified with the same or similar name as the test items in other asterisks. In this study, the structure of these implementation rules is simplified and the same test items are integrated. This is expected to increase the user's understanding of laws and regulations and efficiency.

• Journal of the Korean Society of Safety
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• v.11 no.4
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• pp.143-150
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• 1996

This is an explicit-Implicit, finite element analysis for linear as well as nonlinear hygrothermal stress problems. Additional features, such as moisture diffusion equation, crack element and virtual crack extension(VCE ) method for evaluating J-integral are implemented in this program. The Linear Elastic Fracture Mechanics(LEFM) Theory is employed to estimate the crack driving force under the transient condition for and existing crack. Pores in materials are assumed to be saturated with moisture in the liquid form at the room temperature, which may vaporize as the temperature increases. The vaporization effects on the crack driving force are also studied. The Ideal gas equation is employed to estimate the thermodynamic pressure due to vaporization at each time step after solving basic nodal values. A set of field equations governing the time dependent response of porous media are derived from balance laws based on the mixture theory Darcy's law Is assumed for the fluid flow through the porous media. Perzyna's viscoplastic model incorporating the Von-Mises yield criterion are implemented. The Green-Naghdi stress rate is used for the invariant of stress tensor under superposed rigid body motion. Isotropic elements are used for the spatial discretization and an iterative scheme based on the full newton-Raphson method is used for solving the nonlinear governing equations.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.5
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• pp.25-31
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• 2009

A low power SRAM using supply voltage charge recycling (SVCR-SRAM) scheme is proposed. It divides into two SRAM cell blocks and supplies two different powers. A supplied power is $V_{DD}$ and $V_{DD}/2$. The other is $V_{DD}/2$ and GND. When N-bit cells are accessed, the charge used in N/2-bit cells with VDD and $V_{DD}/2$ is recycled in the other N/2-bit cells with $V_{DD}/2$ and GND. The SVCR scheme is used in the power consuming parts which bit line, data bus, word line, and SRAM cells to reduce dynamic power. The other parts of SRAM use $V_{DD}$ and GND to achieve high speed. Also, the SVCR-SRAM results in reducing leakage power of SRAM cells due to the body-effect. A 64K-bit SRAM ($8K{\times}8$bits) is implemented in a $0.18{\mu}m$ CMOS process. It saves 57.4% write power and 27.6% read power at $V_{DD}=1.8V$ and f=50MHz.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.4
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• pp.114-131
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• 1992

In the present work, a two-dimensional boundary-value problem for a large amplitude motion is treated as an initial-value problem by satisfying the exact body-boundary and nonlinear free-surface boundary conditions. The present nonlinear numerical scheme is similar to that described by Vinje and Brevig(1981) who utilized the Cauchy's theorem and assumed the periodicity in the horizontal coordinate. In the present thesis, however, the periodicity in the horizontal coordinate is not assumed. Thus the present method can treat more realistic problems, which allow radiating waves to infinities. In the present method of solution, the original infinite fluid domain, is divided into two subdomains ; ie the inner and outer subdomains which are a local nonlinear subdomain and the truncated infinite linear subdomain, respectively. By imposing an appropriate matching condition, the computation is carried out only in the inner domain which includes the body. Here we adopt the nonlinear scheme of Vinje & Brevig only in the inner domain and respresent the solution in the truncated infinite subdomains by distributing the time-dependent Green function on the matching boundaries. The matching condition is that the velocity potential and stream function are required to be continuous across the matching boundary. In the computations we used, if necessary, a regriding algorithm on the free surface which could give converged stable solutions successfully even for the breaking waves. In harmonic oscillation problem, each harmonic component and time-mean force are obtained by the Fourier transform of the computed forces in the time domain. The numerical calculations are made for the following problems. $\cdot$ Forced harmonic large-amplitude oscillation(${\omega}{\neq}0,\;U=0$) $\cdot$ Translation with a uniform speed(${\omega}=0,\;U{\neq}0$) The computed results are compared with available experimental data and other analytical results.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4D
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• pp.671-678
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• 2006

In this study, to describe vehicle-structure dynamic interaction phenomena with 1/4 vehicle model, nonlinear Hertzian contact spring and nonlinear contact damper are adopted. The external loads acting on 1/4 vehicle model are selfweight of vehicle and geometry information of running surface. The constraint equation on contact surface is implemented by the Penalty method with stabilization and the reaction from constraint violation. To describe pitching motion of various vehicles two types of the displacement constraint equations are exerted to connect between car bodies and between bogie frames, i.e., the rigid body connection and the rigid body connection with pin, respectively. For the time integration of dynamic equations of vehicles and structure Newmark time integration scheme is adopted. To reduce the error caused by inadequate time step size, adaptive time-stepping technique is also adopted. Thus, it is expected that more versatile dynamic interaction phenomena can be described by this approach and it can be applied to various railway dynamic problems with low computational cost.

• The Journal of Korean Society for School & Community Health Education
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• v.3
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• pp.111-140
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• 2002

This study was conducted from April 1 through April 30, 2002 in order to figure out the relationship between physical health status and life style and the factors influencing physical health. Subjects were selected from among the residents older than 20 years old by probability scheme of one out of 2000. Three thousand people were interviewed by questionnaires, and 2,742(91.4%) respondents were used for analysis, and the results are as follows: 1. Ridit(Relatives to an identified distribution it) of category one by sex was 0.26 in man, and 0.25 in woman. Ridit of category two was 0.57 in man and 0.53 in woman, those of category three was 0.72 in man and 0.65 in woman. That of category four was 0.86 in man and 0.85 in woman, that of category five was 0.95 in man and 0.97 in woman, and that of category six was 0.98 in man and 0.99 in woman. The ridits and health related categories by sex were r=.954 in man and r=.966 in woman(p<0.01) 2. Ridits of healthy behavior 2-1. The ridit of males who slept for less than 6 hrs was 0.71, that of those who slept for $7{\sim}8$ hrs was 0.24, and that of those who slept for more than 9 hours was 0.96. The ridit of females who slept for less than 6 was 0.80, that of those who slept for $7{\sim}8$ hrs was 0.32, and that of those who slept for more than 9 hrs was 0.97. 2-2. The ridit of male, who ate breakfast everyday was 0.30, that of those who ate one to four breakfast per week was 0.87, and that of those who never ate breakfasts was 0.96. The ridit of females who ate breakfast everyday was 0.32, that of those who ate breakfast one to four times a week was 0.75, and that of those who never ate breakfast was 0.99. 2-3. The ridit of males whose body weights were 10% lower than normal body weight was 0.45, that of those with $5{\sim}9.9%$ less than normal body weight was 0.28, that of those with ${\pm}4.9%$ of normal body weight was 0.12, that of those whose body weights were $5{\sim}9.9%$ heavier than normal was 0.40, that of those whose body weights were $10{\sim}19.9%$ heavier than normal was 0.74, that of those with $20{\sim}29.9%$ heavier than normal body weights was 0.78 and that of those with 30% heavier than normal body weight was 0.87. That of females with 10% less than normal body weight was 0.53, that of those with $5{\sim}99%$ less than normal body weight was 0.32, that of 4.9% those with ${\pm}f$ normal body weight was 0.14, that of those with 5.0 to 9.9% heavier body weights was 0.43, that of those with 10 to 19.9% heavier body weight was 0.65, that of those with $20{\sim}29.9%$ heavier body weight was 0.94 and that of those with more than 30% of normal body weight was 0.94. 2-4. The ridit of males who exercised everyday was 0.11, that of those who exercised three to four times a week was 0.25, that of those exercising once or twice a week was 0.48, and that of those who never exercised was 0.80. The ridit of females exercising everyday was 0.08, that of those exercising three to four times a week was 0.21, that of those exercising one to two times was 0.35 and that of those who never exercised was 0.72. 2-5. The ridit of males who did not drink at all was 0.14, that of those who drank one or two cups of hard liquor(Soju) was 0.39, that of those who drank a half bottle of Soju was 0.56, that of those who darnk a bottle of Soju was 0.73 and that of those who drank two bottles of Soju was 0.96. The ridit of females who did not drink at all was 0.30, that of those who drank one or two cups of Soju was 0.70, that of those who drank a half bottle of Soju was 0.84, that of those who drank a bottle of Soju was 0.97 and that of those who drank more than two bottles of Soju was 0.99. 2-6 The ridit of males who did not smoke was 0.20, that of those who smoked one or two cigarettes was 0.44, that of those who smoked about ten cigarettes was 0.58, and that of those who smoked more than a pack of cigarettes was 0.85. The ridit of females who did not smoke at all was 0.90, that of those who smokes one or two cigarettes was 0.91, that of those who smoked about the cigarettes was 0.93 and that of those who smoked more than a pack of cigarettes was 0.96 3. The ridit of males who had healthy behavior in six categories was 0.43 and the average age of them was 45, that of those who had healthy behavior in five categories was 0.47 and the average age was 45, that of those who had healthy behavior in three categories was 0.50 and the average age was 43, that of those who had heathy behavior in two categories was 0.60 and the average age was 40, that of those who had healthy behavior in one category was 0.68 and the average age was 38, and that of those who did not have healthy behavior at all in six categories was 0.79 and the average age was 41. The ridit of females who had heathy behavior in six categories was 0.38 and the average age was 45, that of those who had healthy behavior in five categories was 0.40 and the average age was 44, that of those who had healthy behavior in four categories was 0.46 and the average age was 43, that of those who had healthy behavior in three categories was 0.52 and the average age was 44, that of those who had healthy behavior in two categories was 0.57 and the average age was 41, that of those who the healthy behavior in one category was 0.62 and the average age was 40, and that those who did not have healthy behavior in six categories was 0.79 and the average age was 43. 4. The health statues of the persons who the healthy behavior were better than those who did not have healthy behavior. If the people have healthy behavior in young age and they have healthy education continuously, they can live healthier lives.

• Journal of KIISE:Computing Practices and Letters
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• v.7 no.3
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• pp.260-272
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• 2001

In this paper, we have designed a region-based image retrieval system, FRIP(Finding Region In the Pictures). This system includes a robust image segmentation scheme using color and texture direction and retrieval scheme based on features of each region. For image segmentation, by using a circular filter, we can protect the boundary of round object and merge stripes or spots of objects into body region. It also combines scaled and shifted color coordinate and texture direction. After image segmentation, in order to improve the storage management effectively and reduce the computation time, we extract compact features from each region and store as index. For user interface, by the user specified constraints such as color-care / don't care. scale-care / dont care, shape-care / dont care and location-care / dont care, the overal/ matching score is estimated and the top Ie nearest images are reported in the ascending order of the final score.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.2
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• pp.406-423
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• 2014

The recent advances in wireless communication systems and semiconductor technologies are paving the way for new applications over wireless sensor networks. Health-monitoring application (HMA) is one such emerging technology that is focused on sensing and reporting human vital signs through the communication network comprising sensor devices in the vicinity of the human body. The sensed vital signs can be divided into two categories based on the importance and the frequency of occurrence: occasional emergency signs and regular normal signs. The occasional emergency signs are critical, so they have to be delivered by the specified deadlines, whereas the regular normal signs are non-critical and are only required to be delivered with best effort. Handling the occasional emergency sign is one of the most important attributes in HMA because a human life may depend on correct handling of the situation. That is why the underlying network protocol suite for HMA should ensure that the emergency signs will be reported in a timely manner. However, HMA based on IEEE 802.15.4 might not be able to do so owing to the lack of an appropriate emergency-handling mechanism. Hence, in this paper, we propose a new emergency-handling mechanism to reduce the emergency reporting delay in IEEE 802.15.4 through the modified superframe structure. A fraction of an inactive period is modified into three new periods called the emergency reporting period, emergency beacon period, and emergency transmission period, which are used opportunistically only for immediate emergency reporting and reliable data transmission. Extensive simulation is performed to evaluate the performance of the proposed scheme. The results reveal that the proposed scheme achieves improved latency and higher emergency packets delivery ratio compared with the conventional IEEE 802.15.4 MAC.