Control strategies for flexible operation of power plant with CO2 capture plant

About 20% power output penalties will be incurred for implementing CO₂ capture from power plant. This loss can be partially compensated by flexible operation of capture plant. However, daily large variations of liquid and gas flows may cause operation problems to packed columns. Control schemes were proposed to improve the flexibility of power output without causing substantial hydraulic disturbances in capture plant is presented. Simulations were implemented using ASPEN Plus. In varying lean solvent flow strategy, the flow rate of recycling solvent was manipulated to control the CO₂ capture rate. The liquid flow of the absorber and gas flow of the stripper will vary substantially. In an alternative strategy, the lean solvent loading will be varied. Variation of gas throughput in the stripper is avoided by recycling part of CO₂ vapor to stripper. This strategy provided more stable hydraulics condition in both columns and is recommended for flexible operation. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Achieving spilling-friendly register file assignment for highly distributed register files

Distributed register file architectures divide registers into multiple sets, and it follows that the register files could be small. This can increase the frequency of spilling if register allocation encounters high register pressure, which will reduce the performance. That is, there is extra spilling to handle the pressure and results in performance decline. One of the factors that can produce high pressure is improper register file assignment. Register file assignment is a phase that assigns virtual registers to suitable register files and avoids communication costs. To reduce spilling in the phase of register file assignment, this paper proposes the SPIlling-FRiendly (SPIFR) method, which attempts to improve spilling by estimating the spilling cost from two aspects: assignment and spilling. We used MiBench and EEMBC benchmarks in experiments performed with the Open64-based compiler and a cycle-accurate instruction set simulator. The MiBench experimental results show that the SPIFR method improved the average cycle counts of the benchmarks by 6.0 %. For the kernels of the benchmarks, the method improved the average cycle counts by 20.5 % and reduced the average spilling ratio by 19.0 %. The results on the EEMBC benchmarks indicate that the method improved the cycle counts with the average speedup of 7.0 %, the speedup average of the kernel functions was 11.3 %, and the average reduction in the spilling ratio was 11.7 %, respectively. We conclude that the SPIFR method can reduce spilling and increase the performance.     

Effect of automatic recirculation flow control on the transient response for Lungmen ABWR plant

In this study the automatic mode of the recirculation flow control system (RFCS) for the Lungmen ABWR plant has been modeled and incorporated into the basic RETRAN-02 system model. The integrated system model is then used to perform the analyses for the two transients in which the automatic RFCS is involved. The two transients selected are: (1) one reactor internal pump (RIP) trip, and (2) loss of feedwater heating. In general, the integrated system model can predict well the response of key system parameters, including neutron flux, steam dome pressure, heat flux, RIP flow, core inlet flow, feedwater flow, steam flow, and reactor water level. The transients are also analyzed for manual RFCS case, between the automatic RFCS and the manual RFCS cases, comparisons of the transient response for the key system parameter show that the difference of transient response can be clearly identified. Also, the results show that the ΔCPR (delta critical power ratio) for the transients analyzed may not be less limiting for the automatic RFCS case under certain combination of control system settings.     

Digital Signal Processing with Interleaved ADC Systems

This paper addresses a problem associated with interleaved ADC systems from the digital signal processing algorithm design perspective. The output streams of an interleaved ADC system are inherently in parallel format. It would be nice if DSP algorithms can be designed to take advantage of the inherently parallel signal streams in the interleaved ADC system without the need of a high speed parallel-to-serial multiplexer. Frequency response of a parallel filter bank is derived. It is found that the overall frequency response is the average of each individual interpolated channel filter plus the aliasing components. The aliasing components come from the deviation of each individual channel from the average response.Results are applied to characterize the gain mismatch of ADC arrays. Sinusoidal response is also investigated. The results can be used to characterize the frequency response mismatch of ADC arrays.Yih-Chyun Jenq received the B.S.E. degree from National Taiwan University, Taipei, Taiwan in 1971, and the M.S.E., M.A., and Ph.D. degrees in Electrical Engineering from Princeton University, Princeton, NJ in 1974, 1975, and 1976, respectively. From 1976 to 1980, he was Assistant Professor of Electrical Engineering at the State University of New York at Stony Brook, Stony Brook, NY. From 1980 to 1984, he was a Member of Technical Staff at AT&T Bell Laboratories, Homdel, NJ. From 1984 to 1990, he was a Research Manager and Principal Engineer at Tektronix Laboratories, Beaverton, OR. In September 1990, he joined the Faculty of the Department of Electrical and Computer Engineering at Portland State University, Portland, OR where he is currently a Full Professor. From 1987 to 1989, Dr. Jenq served as Associate Editor of the IEEE Transactions on Circuits and Systems in charge of Digital Signal Processing. He was the recipient of the 1988 Andrew R. Chi Prize Paper Award of the IEEE Instrumentation and Measurement Society. He holds ten (10) U.S. patents. Dr. Jenq is a fellow of the IEEE.     

Geometric error calibration of multi-axis machines using an auto-alignment laser interferometer

This work will report the development and application of an auto-alignment laser interferometer system for the geometric error calibration of CNC multi-axis machines. The system is capable of a diagonal displacement measurement, where multiple machine axes are moved simultaneously, with automatic optic alignment. This capability provides a solution for quick evaluation of the overall volumetric error of a multi-axis machine tool. One application of the system is that the 21 geometric errors of a 3-axis machine can be quickly estimated from the displacement measurements of some determined diagonal lines in the working volume. Compared with a time of several days using a conventional laser interferometer system, it takes only 1 hour for the proposed system to complete the geometry calibration of a 3-axis machine. A method for the roll calibration of a vertical axis is also proposed and demonstrated in this work.     

Waveform estimation with jitter noise using stochastic up and downmethod

Jitter noise exists, especially, when sampling high-frequency waveforms. This paper aims to address this problem through a stochastic method. By studying the stochastic up and down method in detail, we propose a “ratio indicator”, which can supplement the basic stochastic up and down method. Simulation results show that the proposed method gives good estimates with known error bounds     

Sinewave parameter estimation algorithm with application towaveform digitizer effective bits measurement

The authors present a high-performance (i.e. high-precision and high-speed) algorithm to estimate the four parameters of a sine wave from a sampled data record. The estimation errors are derived in closed form, and hence, controllable. The authors then propose a method to measure a digitizers effective bits based on this algorithm. Simulation results indicate that the proposed method gives excellent estimates of the true resolution of the simulated ideal digitizer. This proposed algorithm is noniterative and gives swift and consistent results     

Improving Timing Offset Estimation by Alias Sampling

In a previous paper, we reported an algorithm that can be used to accurately measure sampling timing errors in a data acquisition system that encounters nonuniform sampling. In this paper, we first study the sensitivity of the algorithm to input frequency inaccuracy. We then investigate the dependency of the accuracy of the algorithm on the number of effective bits in an analog-to-digital (A/D) converter. It is observed that, if the initial timing error is "reasonably large," then the residual timing error decreases by one order of magnitude for each increase in the number of effective bits by four. Finally, we propose the use of "alias sampling" to "magnify" the timing error so that the algorithm's sensitivity is greatly improved and can be used to estimate a much smaller timing offset with only a modest number of effective bits in the A/D converter.     

Low temperature sintering and crystallisation behaviour of low loss anorthite-based glass-ceramics

Anorthite-based glass-ceramics including TiO₂ as nucleating agent were melted and quenched in this study. The effect of particle size on the sintering behaviour of glass powders was investigated in order to obtain low-temperature sintered glass-ceramics. Anorthite glass-ceramic starts to densify at the transition temperature of glass (T _g = 770°C) and is fully sintered before the crystallisation occurrence (880°C). Therefore, a dense and low-loss glass-ceramic with predominant crystal phase of anorthite is achieved by using fine glass powders (D ₅₀ = 0.45 m) fired at 900°C. The as-sintered density approaches 99% theoretical density and the apparent porosity is as low as 0.05 Vol%. The dense and crystallized anorthite-based glass-ceramic exhibits a fairly low dielectric loss of 4 × 10^–4 at 1 MHz and a thermal expansion coefficient of 4.5 × 10^–6°C^–1. Furthermore, the microwave characteristics were measured at 10 GHz with the results of K = 9.8, Q _f = 2250, and temperature coefficient of resonant frequency _f = –30 ppm/°C.