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Jae-Sung Mun Keun-Hyeok Yang Yong-Soo JeonAbstractThe purpose of this study is to propose a simple model to evaluate the compressive strength development of concrete with various supplementary cementitious materials (SCMs) and cured under different temperatures. For the generalization of the model,the ACI 209 parabola equation was modified based on the maturity function and then experimental constants A and B and 28-daycompressive strength were determined from the regression analysis using a total of 265 data-sets compiled from the available literature. To verify the proposed model, concrete specimens classified into 3 Groups were prepared according to the SCM level as a partial replacement of cement and curing temperature. The analysis of existing data clearly revealed that the 28-day compressive strength decreases when the curing temperature is higher and/or lower than the reference curing temperature (20℃). Furthermore, test results showed that the compressive strength development of concrete cured under 20℃ until an early age of 3days was marginally affected by the curing temperature afterward. The proposed model accurately predicts the compressive strengthdevelopment of concrete tested, indicating that the mean and standard deviation of the ratios between predictions and experiments are 1.00 and 0.08, respectively.Keywords : Maturity function, Compressive strength development, Supplementary cementitious materials, Curing temperature

The performance of a pre-amplified cross-phase modulation (XPM) wavelength converter has been theoretically investigated. We showed that the pre-amplifier enhances the input optical power dynamic range by 3 dB. The additional 4-dB improvement of the power penalty in wavelength conversion obtained through BER simulation shows that integrating a pre-amplifier enables the accommodation of a relatively small input optical power. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 131–134, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10697

Genetic algorithms are applied here to optimize the control gains of a three-loop controller for a pneumatic servo cylinder drive. The three-loop controller has position, velocity, and acceleration feedback gain, all of which have formerly been manually tuned. A general procedure for optimizing the control parameters of fluid power systems by using genetic algorithms is presented. It is shown that, by using minimum information specific to the system, near-optimal values of the control gains can be obtained within 10 generations. It is also shown that the numerical values of both the optimal velocity and the acceleration gain tend to increase as either the load mass or reference position increases, when the optimal position gain is fixed at a constant value. The optimized gains are confirmed by a plot of the fitness distribution defined in this study, which represents the control performance of the system in a given gain space.

An analysis of a cross-phase modulation (XPM) wavelength converter integrated with preamplifers for increased input power dynamic range is reported. The performance of the preamplified wavelength converter can be deteriorated by the residual reflectivity of semiconductor optical amplifiers (SOAs) inside the converter. We investigate the trade-off relationship between the internal reflectivity of SOAs and the performance of the XPM wavelength converter with an integrated preamplifier through bit error rate (BER) calculation. The optimal physical and operating parameters of the preamplified XPM wavelength converter are proposed.