@article{frey_zhu_2006, title={Improved system integration for integrated gasification combined cycle (IGCC) systems}, volume={40}, ISSN={["0013-936X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33644869596&partnerID=MN8TOARS}, DOI={10.1021/es0515598}, abstractNote={Integrated gasification combined cycle (IGCC) systems are a promising technology for power generation. They include an air separation unit (ASU), a gasification system, and a gas turbine combined cycle power block, and feature competitive efficiency and lower emissions compared to conventional power generation technology. IGCC systems are not yet in widespread commercial use and opportunities remain to improve system feasibility via improved process integration. A process simulation model was developed for IGCC systems with alternative types of ASU and gas turbine integration. The model is applied to evaluate integration schemes involving nitrogen injection, air extraction, and combinations of both, as well as different ASU pressure levels. The optimal nitrogen injection only case in combination with an elevated pressure ASU had the highest efficiency and power output and approximately the lowest emissions per unit output of all cases considered, and thus is a recommended design option. The optimal combination of air extraction coupled with nitrogen injection had slightly worse efficiency, power output, and emissions than the optimal nitrogen injection only case. Air extraction alone typically produced lower efficiency, lower power output, and higher emissions than all other cases. The recommended nitrogen injection only case is estimated to provide annualized cost savings compared to a nonintegrated design. Process simulation modeling is shown to be a useful tool for evaluation and screening of technology options.}, number={5}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Frey, HC and Zhu, YH}, year={2006}, month={Mar}, pages={1693–1699} }
 @article{zhu_rouskas_perros_2000, title={A comparison of allocation policies in wavelength routing networks}, volume={2}, ISSN={["1572-8188"]}, DOI={10.1023/A:1010056408572}, number={3}, journal={PHOTONIC NETWORK COMMUNICATIONS}, author={Zhu, YH and Rouskas, GN and Perros, HG}, year={2000}, month={Aug}, pages={267–295} }
 @article{zhu_rouskas_perros_2000, title={A path decomposition approach for computing blocking probabilities in wavelength-routing networks}, volume={8}, ISSN={["1558-2566"]}, DOI={10.1109/90.893871}, abstractNote={We study a class of circuit-switched wavelength-routing networks with fixed or alternate routing and with random wavelength allocation. We present an iterative path decomposition algorithm to evaluate accurately and efficiently the blocking performance of such networks with and without wavelength converters. Our iterative algorithm analyzes the original network by decomposing it into single-path subsystems. These subsystems are analyzed in isolation, and the individual results are appropriately combined to obtain a solution for the overall network. To analyze individual subsystems, we first construct an exact Markov process that captures the behavior of a path in terms of wavelength use. We also obtain an approximate Markov process which has a closed-form solution that can be computed efficiently for short paths. We then develop an iterative algorithm to analyze approximately arbitrarily long paths. The path decomposition approach naturally captures the correlation of both link loads and link blocking events. Our algorithm represents a simple and computationally efficient solution to the difficult problem of computing call-blocking probabilities in wavelength-routing networks. We also demonstrate how our analytical techniques can be applied to gain insight into the problem of converter placement in wavelength-routing networks.}, number={6}, journal={IEEE-ACM TRANSACTIONS ON NETWORKING}, author={Zhu, YH and Rouskas, GN and Perros, HG}, year={2000}, month={Dec}, pages={747–762} }
 @article{hassan_zhu_matzen_1998, title={Improved ratcheting analysis of piping components}, volume={75}, ISSN={["0308-0161"]}, DOI={10.1016/S0308-0161(98)00070-2}, abstractNote={It is well known that ratcheting (defined as the accumulation of deformation with cycles) can reduce fatigue life or cause failure of piping components or systems subjected to seismic or other cyclic loads. This phenomenon is sometime referred to as fatigue-ratcheting, which is yet to be understood clearly. Commercial finite element codes cannot accurately simulate the ratcheting responses recorded in tests on piping components or systems. One of the reasons for this deficiency has been traced to inadequate constitutive models in the existing analysis codes. To overcome this deficiency, an improved cyclic plasticity model, composed of the Armstrong–Frederick kinematic hardening rule and the Drucker–Palgen plastic modulus equation, is incorporated into an ANSYS material model subroutine. The modified ANSYS program is verified against three sets of experimental results. The simulations from this modified ANSYS show a significant improvement over the unmodified ANSYS and the ABAQUS codes.}, number={8}, journal={INTERNATIONAL JOURNAL OF PRESSURE VESSELS AND PIPING}, author={Hassan, T and Zhu, Y and Matzen, VC}, year={1998}, month={Jul}, pages={643–652} }