• Journal of the Korean Society of Safety
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• v.17 no.3
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• pp.107-111
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• 2002

A near extinction nonpremixed counterflow flame of 19% methane diluted by 81% nitrogen by volume and undiluted air at a low global strain rate, 20 s-1, was computed. Investigations were focused on effects of the duct thickness and velocity boundary conditions on the flame structure in normal and zero gravity conditions. The results showed that, under normal gravity conditions, the effects of the duct thickness and velocity boundary conditions were significant by shifting the flame position, but negligible in zero gravity. The differences in flame structure were caused by buoyancy, and hence should be considered in the measurements in normal gravity.

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.6
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• pp.91-96
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• 2009

This study describes a zero discharge and reuse system developed for rural areas. The purpose of the system is decontamination of used irrigation water for down-stream usage and reuse of wastewater in rural villages for preventing water shortage problem expected to happen in near future. The system consists of anoxic, FES (Ferrous Electricity System), Oxic, Cralifier processes. The main feature of the system is to remove phosphorous by using Fe-ionizing module. Indoor experiments were undertaken with a trial product of the system to test its performance. The removal capacities of T-P, T-N, and BOD were examined. Also the proper time for the replacement of iron plate module was tested as well as the efficiency of T-P removal rate based on the usage of an automatic washing system for the iron plate. As results, the system showed very good water purification performances through obtaining the results of over 90% removal rates from T-P, BOD, and 67% from T-N. The proper time period for replacement of iron plate was maximum 2 years, and also efficiency of T-P removal rate found to be greatly influenced by the usage of an automatic washing system from the test.

• Journal of Power Electronics
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• v.17 no.1
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• pp.88-95
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• 2017

To reduce common-mode voltage (CMV), various reduced CMV pulse width modulation (RCMV-PWM) algorithms have been proposed, including active zero state PWM (AZSPWM) algorithms, remote state PWM (RSPWM) algorithms, and near state PWM (NSPWM) algorithms. Among these algorithms, AZSPWM algorithms can reduce CMV, but they increase the number of switchings compared to the conventional space vector PWM (CSVPWM). This paper presents a new AZSPWM algorithm for reductions in both the CMV and total number of switchings in BLAC motor drives. Since the proposed AZSPWM algorithm uses only active voltage vectors for motor control, it reduces CMV by 1/3 compared to CSVPWM. The proposed AZSPWM algorithm also reduces the total number of switchings compared to existing AZSPWM algorithms by eliminating the switchings required from one sector to the next. The performance of the proposed algorithm is verified by analyses, simulations, and experimental results.

• Korean Journal of Optics and Photonics
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• v.4 no.3
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• pp.252-259
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• 1993

A holosymmetric four-mirror system with unit magnification is designed for use in the micro-lithography using a deep ultraviolet wavelength of $0.248 {\mu}m$(KrF excimer laser line). In the holosymmetric system all orders of coma and distortion are zero. By applying this principle to the 4-spherical mirror system, we have obtained only one exact solution for the unit magnification holosymmetric four-spherical mirror system with all zero third order aberrations. For correction of the residual higher order aberrations of the system, aspherization is introduced keeping the holosymmetric properties. We have obtained near diffraction-limited performance for the wavelength of 0.248 pm within N.A. of 0.33 and image field diameter of 7.6 mm.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.354-359
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• 2001

As the temperature of liquid under negative pressure approaches the absolute zero, the nucleation process due to thermal fluctuations hardly occurs. Instead of this mechanism, quantum fluctuations may lead the formation of nucleus for new phase in metastable state. In this study, the thermal as well as quantum nucleation bubble in liquid helium under negative pressure was investigated theoretically. The energy barrier against nucleation was estimated by molecular interaction due to the Londom dispersion force. It is shown that the phase transition from liquid to vapor in is possible due to the quantum tunneling below 0.2 K for Helium-4 and 0.1 K for Helium-3, at negative pressures close to the ideal tensile strength at which every liquid molecules become bubbles simultaneously.

• Journal of the military operations research society of Korea
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• v.31 no.1
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• pp.107-121
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• 2005

In this study, a new fictitious play (FP) procedure is presented to solve two-person zero-sum (TPZS) Blotto games. The FP solution procedure solves TPZS games by assuming that the two players take turns selecting optimal responses to the opponent's strategy observed so far. It is known that FP converges to an optimal solution, and it may be the only realistic approach to solve large games. The algorithm uses dynamic programming (DP) to solve FP subproblems. Efficiency is obtained by limiting the growth of the DP state space. Blotto games are frequently used to solve simple missile defense problems. While it may be unlikely that the models presented in this paper can be used directly to solve realistic offense and defense problems, it is hoped that they will provide insight into the basic structure of optimal and near-optimal solutions to these important, large games, and provide a foundation for solution of more realistic, and more complex, problem

• Journal of the Chungcheong Mathematical Society
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• v.19 no.2
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• pp.133-139
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• 2006

By combining the classical Newton's method with the pseudo-secant method, pseudo-secant-Newton's method is constructed and its order and rate of convergence are investigated. Given a function $f:\mathbb{R}{\rightarrow}\mathbb{R}$ that has a simple real zero ${\alpha}$ and is sufficiently smooth in a small neighborhood of ${\alpha}$, the convergence behavior is analyzed near ${\alpha}$ for pseudo-secant-Newton's method. The order of convergence is shown to be cubic and the rate of convergence is proven to be $\(\frac{f^{{\prime}{\prime}}(\alpha)}{2f^{\prime}(\alpha)}\)^2$. Numerical experiments show the validity of the theory presented here and are confirmed via high-precision programming in Mathematica.

• Journal of Information Processing Systems
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• v.9 no.3
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• pp.461-476
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• 2013

Recently, smart devices for various services have been developed using converged telecommunications, and the markets for near field communication mobile services is expected to grow rapidly. In particular, the realization of mobile NFC payment services is expected to go commercial, and it is widely attracting attention both on a domestic and global level. However, this realization would increase privacy infringement, as personal information is extensively used in the NFC technology. One example of such privacy infringement would be the case of the Google wallet service. In this paper, we propose an zero-knowledge proof scheme and ring signature based on NTRU for protecting user information in NFC mobile payment systems without directly using private financial information of the user.

• Journal of the korean Society of Automotive Engineers
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• v.14 no.4
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• pp.79-89
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• 1992

The behavior of belt tension in OHC drive timing belt system was investigated analytically and experimentally for (1)fixed and (2)automatic tensioner. From the numerical results it was found that the automatic tensioner makes the belt tension larger than those of the fixed tensioner. When the initial belt tension decreased due to the belt elongation, the belt tension of the fixed tensioner could decrease to near zero while the belt tension for the automatic tensioner maintained above zero by the tensioner spring. The mean valve and the difference between the maximum and the minimum belt tension for the automatic tensioner increased compared with those of the fixed tensioner. Also, the numerical results for a hydraulic tensioner showed that the hydraulic tensioner has the good parts of both tensioners; i.e., thesmaller amplitude in belt tension and the higher mean tension. Experimental results for the automatic and fixed tensioner of the OHC timing belt system were in agreement with the theoretical results.

• The Pure and Applied Mathematics
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• v.4 no.1
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• pp.61-69
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• 1997

In this paper, we study the dynamics of a two-parameter unfolding system $\chi$' = y, y' = $\beta$y＋$\alpha$f($\chi\alpha\pm\chiy$＋yg($\chi$), where f($\chi$,$\alpha$) is a second order polynomial in $\chi$ and g($\chi$) is strictly nonlinear in $\chi$. We show that the higher order term yg($\chi$) in the system does not change qulitative structure of the Hopf bifurcations near the fixed points for small $\alpha$ and $\beta$ if the nontrivial fixed point approaches to the origin as $\alpha$ approaches zero.