• 한국전기전자재료학회논문지
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• 제13권4호
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• pp.286-293
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• 2000

In this paper we investigated the structural dielectric and piezoelectric properties of 0.03Pb(Sb$\_$1/2//Nb$\_$1/2/)-0.97Pb(Zr$\_$0.495//Ti$\_$0.505/)O$_3$+0.5 wt% excess PbO + wt% MnO(X=0, 0.1, 0.3, 0.5, 0.7) ceramics to develop the high-power piezoelectric transformer. The piezoelectric transformers with dimension of 27.5$\times$27.5$\times$2.5［mm$^3$］were fabricated and their electrical properties were measured. Maxima of piezoelectric properties such as electro-mechanical coupling factor of 0.534 and mechanical quality factor of 1487 were obtained for the PSN-PZT with 0.3wt% MnO. voltage step-up ratios of piezoelectric transformers at 500［Ω］and no load were 0.78, 12.82, respectively. The maximum efficiency of piezoelectric transformer was 98.6% at 800［Ω］. While the 14W fluorescent lamp were driven by the piezoelectric transformer for more than 20［min］, increment of temperature in the piezoelectric transformer was 7［$\^{C}$］.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1995년도 가을 학술발표회 논문집
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• pp.185-193
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• 1995

The softening behaviors of concrete have been the object of numerous experimental and numerical studies, because the load carrying capacity of cracked concrete structure is not zero. Numerical studies are devoted to the investigation of three-dimensional softening behaviors of concrete on the basis of a viscoplastic theory, which may be able to represent the effects of plasticity and also of rheology. In order to properly describe material behaviors corresponding to different stress levels, two surfaces in stress space are adopted; one is a yield surface, and the other is a failure or bounding surface. When a stress path reaches the failure surface, it is considered that the softening behaviors are initiated as micro-cracks coalesce and are simulated by assuming that the actual strain increments in the post-peak region are less than the equivalent viscoplastic strain increment. The experimental studies and the finite element analyses have been carried out under the displacement control. Numerically simulated results indicate that the model is able to predict the essential characteristics of concrete behaviors such as the non-linearity, stiffness degradation, different behaviors in tension and compression, and specially dilatation under uniaxial compression.

• 한국환경보건학회지
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• 제30권2호
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• pp.133-139
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• 2004

The objective of this study was to investigate the destruction efficiency and to determine the fundamental parameters of oxidation kinetics under the supercritical water(SCW) condition. Target material was cephradine, toxic and antibiotic material, in the pharmaceutical wastewater. For this purpose, the effect of reaction temperature and oxidant were investigated on the destruction efficiency of cephradine. And the oxidation kinetics of cephradine was derived by using a empirical power-law model. The experiment was carried out in a cylindrical batch reactor made of Hastelloy C-276 which was endurable high temperature and pressure. The destruction efficiency of cephradine increased with increment of the temperature and reaction time. Also the type of oxidants was effected and oxidants(Air and $H_2O$$_2$) were enhanced the destruction efficiency. The global oxidation kinetics for cephradine has led to two rate expressions according to type of oxidant. - In the presence of air oxidant: Rate=k. $e^{-Ea}$RT/(Ceph.)$^{1.0}$ ( $O_2$)$^{0.51}$$\pm$0.05(k=3.27${\times}$$10^{5}$ sec. Ea=63.25 kJ/mole) - In the presence of $H_2O$$_2$ oxidant : Rate=kㆍ $e^{-Ea}$RT/(Ceph.)$^{1.0}$ ($H_2O$$_2$)$^{0.62}$$\pm$0.02(k=2.76${\times}$$10^4$/sec. Ea=47.65 kJ/mole)ole))

• 대한산업공학회지
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• 제30권1호
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• pp.65-75
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• 2004

The enhancement of C2(Command and Control) system will increase effectiveness of individual force power in combat engagement. Especially, available time of a given engaging force and information accuracy are the most influencing factors to increment of combat effectiveness after enhancement of C2 system. In this paper, by using Schutzer's C2 Theory and Measures of Effectiveness, we developed several analytical functions representing the relationships between C2 system enhancement and two most critical variables, available time and information accuracy. As a result of functional analysis, we showed C2 system enhancement and combat effectiveness have positive and non-linear relationship. The higher level of C2 system be required, the better combat effectiveness of force power can be obtained. Additionally, we proposed a proposition that the combat effectiveness of C2 system is more sensitive to available time than to information accuracy, which might be very important issue for further research in this field.

• Nuclear Engineering and Technology
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• 제44권5호
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• pp.543-550
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• 2012

The decrease in the fracture toughness of ferritic steels in a reactor pressure vessel is an important factor in determining the lifetime of a nuclear power plant. A surveillance program has been in place in Korea since 1979 to assess the structural integrity of RPV steels. In this work, the surveillance data were collected and analyzed statistically in order to derive the empirical relationship between the embrittlement and strengthening of irradiated reactor pressure vessel steels. There was a linear relationship between the yield strength change and the transition temperature shift change at 41 J due to irradiation. The proportional coefficient was about $0.5^{\circ}C$/MPa in the base metals (plate/forgings). The upper shelf energy decrease ratio was non-linearly proportional to the yield strength change, and most of the data lay along the trend curve of the US results. The transition regime temperature interval, ${\Delta}T_T$, was less than the US data. The overall change from irradiation was very similar to the US results. It is expected that the results of this study will be applied to basic research on the multiscale modeling of the irradiation embrittlement of RPV materials in Korea.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.823-825
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• 1996

This paper proposes a preventive maintenance scheduling system which is a user-friendly decision-making support system. The objective of the development of the package is to supply KEPCO's working experts with a useful tool for gaining a practical maintenance schedule. This program based on the MS Windows is made up of two main modules. The first is an interactive decision-making support module(IDSM). The main objective of this module is to provide various useful text and graphic information to users, and enable practicing engineers with sensitivity analysis of a targeting maintenance schedule. The second is a mathematical optimization module(MOM). In this module, the objective function of levelizing net reserve ratio with daily time-increment is optimized using the relaxation method.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2008년도 추계학술대회 초록집
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• pp.15-16
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• 2008

In case manufacturing COF, through hole should be made to be used for a pathway connecting the conductive layers of its both faces. In case Cu-plating inside of through hole with electroless plating way, contact between Cu and PI film gets bad to be fell apart from PI by the impact of applying to the electric devices. Therefore, after sputtering is applying on inner through hole, then a method to perform electroplating process. In this study, after changing sputtering condition to manufacture FCCL, we looked the changeability of the upper PI and inner hole Cu layers. Making use of RF Magnetron sputtering equipment, we coated Cu thin film and Cu-plated on it through electroplating. After cold-mounting the completed FCCL, we examined hole section through an optical microscope. From the result of test, with parameters deposition pressure and deposition time, both the thickness of the hole plated layer and PI plated upper layer increased at regular rate, increasing the thickness of Cu sputter layer. However, from the result of test in increasing RF-power, we could know the increment rate of hole plated layer is considerably greater than that of PI plated upper layer. Therefore, we finally acquired good result; if you want only to increase the plated layer of inner hole, it's much better to increase RF-power.

• Nuclear Engineering and Technology
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• 제53권7호
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• pp.2084-2094
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• 2021

Delta-form-based methods for solving high order spatial discretization schemes are introduced into the reactor S_N transport equation. Due to the nature of the delta-form, the final numerical accuracy only depends on the residuals on the right side of the discrete equations and have nothing to do with the parts on the left side. Therefore, various high order spatial discretization methods can be easily adopted for only the transport term on the right side of the discrete equations. Then the simplest step or other robust schemes can be adopted to discretize the increment on the left hand side to ensure the good iterative convergence. The delta-form framework makes the sweeping and iterative strategies of various high order spatial discretization methods be completely the same with those of the traditional S_N codes, only by adding the residuals into the source terms. In this paper, the flux limiter method and weighted essentially non-oscillatory scheme are used for the verification purpose to only show the advantages of the introduction of delta-form-based solving methods and other high order spatial discretization methods can be also easily extended to solve the S_N transport equations. Numerical solutions indicate the correctness and effectiveness of delta-form-based solving method.

• 대한전자공학회논문지
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• 제24권1호
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• pp.91-96
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• 1987

Plasma etching can obtain less damaged etch surface than reactive ion etching. This study was performed to get anisotropic etching characteristics of Si using two step etching technique with C2CIF5 and SF6 gas mixture. The results show that the etch rate and aspect ratio of silicon was increased with increment of SF6 contents. The bulging phenomenon on trench side wall in the plasma one-step etching technique was eliminated by the two step etching technique. The anisotropy was decreased from 12(at 120m Torr) to 2.2(at 400m Torr) with increasing the chamber pressure. At the low rf power (350 watts) anisotrpy of silicon was obtained 7 lower than that of high rf power (650 watts. A:~9). In Summary we obtained anisotropic etching profiles of silicon with e 6\ulcornerm depth by using the plasma two-step etching technique.

• JSTS:Journal of Semiconductor Technology and Science
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• 제12권4호
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• pp.397-404
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• 2012

Thermal generation by power dissipation of the highly integrated System on Chip (SoC) device is irregularly distributed on the intra chip. It leads to thermal increment of the each thermally different region and effects on the propagation timing; consequently, the timing violation occurs due to the misestimated number of buffers. In this paper, the timing budgeting methodology considering thermal variation which contains buffer insertion with wire segmentation is proposed. Thermal aware LUT modeling for cell intrinsic delay is also proposed. Simulation results show the reduction of the worst delay after implementing thermal aware buffer insertion using by proposed wire segmentation up to 33% in contrast to the original buffer insertion. The error rates are measured by SPICE simulation results.