• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.6
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• pp.609-617
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• 2011

There is a trend towards the progressive use of higher operating temperatures and stresses to achieve improved efficiencies in power-generation equipment. It is important to perform the crack assessment under hightemperature and high-pressure conditions. The C(t)-integral is a key parameter in crack assessment for transient creep states. The estimation of the C(t)-integral is complex when considering the mechanical and thermal loads simultaneously. In this paper, we study estimation of C(t)-integral under combined mechanical and thermal load depending on loading conditions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.9
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• pp.851-857
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• 2015

In this paper, we estimate the time-dependent C(t) integrals under elastic-plastic-creep conditions. Finite-element (FE) transient creep analyses have been performed for single-edge-notched-bend (SEB) specimens. We investigate the effect of the initial plasticity on the transient creep by systematically varying the magnitude of the initial step load. We consider both the same stress exponent and different stress exponents in the power-law creep and plasticity to elastic-plastic-creep behavior. To estimate the C(t) integrals, we compare the FE analysis results with those obtained using formulas. In this paper, we propose a modified equation to predict the C(t) integrals for the case of creep exponents that are different from the plastic exponent.

• Journal of the KSME
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• v.27 no.2
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• pp.132-136
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• 1987

최근 저자는 혼합모우드에 대한 Budiansky와 Rice의 $J_k$ 적분에 모순이 있음을 지적한 바 있다. 그러나, Kishimoto등은 파괴진행영역을 고려한 경로 독립적분J/^/을 제시하여 주목을 끌고 있다. Landes등은 Rice의 J적분을 정상상태 크리이프에까지 연장 적용하기 위한 $C^*$적분을 소개하였다. 그후 크리이프파괴에 대한 매개변수로서 Liu등에 의한 $C_{gk}{\;}^*$, Brust등에 의한 $T_k{\}^*$등이 소개되어 계속 연구중이다. 여기에서는 이러한 매개변수들에 대해 개괄적으로 서술하고자 한다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.9
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• pp.62-71
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• 2002

An intergral C-V converter is proposed to solve the nonlinearity problem of capacitive pressure sensors. The integral C-V converter consists of a switched-capacitor integrator and a switched-capacitor differential amplifier. It converts the sensor capacitance change which is inversely proportional to an applied pressure into a linear voltage output. Various PSPICE simulations prove that the convertor has excellent characteristics, such as low nonlinearity less than 0.01%/FS and low sensitivity to parallel offset capacitance and parasitic capacitance for the displacement range of sensor diaphragm set to 0 ${\sim}$ 90% of the initial distance between the electrodes in the simulation. We also show that the offset compensation and the gain trimming are easily achieved with the integral C-V converter.

• Journal of Industrial Technology
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• v.20 no.A
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• pp.203-209
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• 2000

The fluctuation integrals which give useful information in the structure of solution are associated with the mixed direct correlation integral ($C_{12}$) known. Using its weighted arithmetic mean of $C_{11}$ and $C_{22}$ and the activity coefficient model, the fluctuation integrals on solute-solute, solvent-solute, and solvent-solvent can be calculated in the function of mole fraction. In this work, several binary mixtures containing c-hexane were tested and the results on the fluctuation integrals were rather good.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.1
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• pp.77-86
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• 1989

A modified $C^{*}$ integral as load parameter in creep fracture is proposed considering the effect of crack growth. It is shown that the parameter does not depend on crack velocity. By performing experiment using STS 304 stainless steel at 600.deg.C the validity of the parameter is investigated. The results show that the parameter is a good measure as a load parameter in creep fracture and the rate of crack tip opening displacement can also be a creep load parameter for STS 304 at 600.deg. C.C.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.9
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• pp.64-72
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• 1998

In this paper, the design of a current integrator for low-voltage, low-power, and high frequency applications using complementary high swing cascode current-mirror is presented. The proposed integrator decreases output current errors due to non-zero input resistance and non-infinite output resistance of the simple current integrator. As a design example, the 3rd order Butterworth lowpass filter is designed by a leapfrog method. Also, we apply the predistortion design method to reduce the magnitude distortion which occurs at a cutoff frequency by the undesirable phase shift of a lossless current integrator. The designed current-mode filter is simulated and examined by SPICE using 0.8$\mu\textrm{m}$ CMOS n-well process parameters. The simulation results show 20MHz cutoff frequency and 615㎼ power dissipation with a 2V power supply. And the cutoff frequency of the filters can be easily changed by the DC bias current.

• Communications of Mathematical Education
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• v.36 no.1
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• pp.39-57
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• 2022

This study aims to design an integral instruction method that follows the Abstraction in Context (AiC) framework proposed by Hershkowitz, Schwarz, and Dreyfus to help students in acquiring in-depth understanding of the relationship between indefinite integrals and definite integrals and to analyze how the students' understanding improved as a result. To this end, we implemented lessons according to the integral instruction method designed for eight 11th grade students in a science high school. We recorded and analyzed data from graded student worksheets and transcripts of classroom recordings. Results show that students comprehend three knowledge elements regarding relationship between indefinite integral and definite integral: the instantaneous rate of change of accumulation function, the calculation of a definite integral through an indefinite integral, and The determination of indefinite integral by the accumulation function. The findings suggest that the AiC framework is useful for designing didactical activities for conceptual learning, and the accumulation function can serve as a basis for teaching the three knowledge elements regarding relationship between indefinite integral and definite integral.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.7
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• pp.521-527
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• 2014

Most of Sea Surveillance Radar(SSR)s which are used in Vessel Traffic Service are Magnetron-based Non-Coherent Method and use the pulse integration technique having a signal to noise ratio enhancement function to satisfy a surveillance performance about target. Especially, Pulse Integration technique has an effect on target serveillance performance through signal to noise ratio, in addition, has an effect to improve a signal interference and noise spike. In this paper, we have a simulation experiment by using MATLAB simulation tool for appling a pulse integration technique in VTS system using a Non-Coherent radar, and verify an optimum pulse integration technique through out performance analysis between frequently use pulse integration techniques.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.6
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• pp.30-38
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• 1998

In this paper, a new CMOS current-mode integrator is proposed that can apply the basic building block of the low-voltage high frequency current-mode active filter. And tuning circuits that control the gain and unity gain frequency of them is designed. The proposed integrator is composed of the CMOS complementary circuit which can extend transconductance of an integrator. Therefore, the unity gain frequency which is determined transconductance and MOSFET gate capacitance can be expanded by the proposed integrator. The unity gain frequency of the proposed integrator is increased about two times larger than that of the conventional continuous-time integrator with NMOS-gm. And also, cut-off frequency and gain of the active filter can be controlled with the designed tuning circuit. From the result, we can reduce errors on fabrication. And then, 3rd-order low-pass active filter is designed as an application circuits. These results are verified by the small signal analysis and the 0.8$\mu\textrm{m}$ parameter HSPICE simulation.