Design and optimization of industrial power systems for natural gas processing

Xuesong Zheng,김진국 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.8

This paper presents a novel design methodology for power systems. A superstructure-based modelling technique has been applied to identify the cost-effective match between available power generation equipment and energy consumers. Multi-period design is conducted to ensure accurate equipment performance estimation. The proposed MILP (mixed integer linear programming) optimization model is able to reflect the machinery performance variations affected by the environmental conditions, and to estimate the deteriorated machinery performance due to part-load operation. To maintain the linear nature of the overall mathematical model, machinery performance is linearized with reasonable accuracy. Moreover, the multi-period methodology is able to conduct synthesis of power systems for processes with non-constant energy demands. Case studies are illustrated to demonstrate the importance of considering the effect of ambient conditions and part-load operation on machinery performance. With the ability to satisfy varying energy demands, and more accurate description of the machinery performance, the optimal design yielded from the improved model would exhibit better flexibility and reliability.

Numerical and experimental study of multi-bench retained excavations

Zheng, Gang,Nie, Dongqing,Diao, Yu,Liu, Jie,Cheng, Xuesong Techno-Press 2017 Geomechanics & engineering Vol.13 No.5

Earth berms are often left in place to support retaining walls or piles in order to eliminate horizontal struts in excavations of soft soil areas. However, if the excavation depth is relatively large, an earth berm-supported retaining system may not be applicable and could be replaced by a multi-bench retaining system. However, studies on multi-bench retaining systems are limited. The goal of this investigation is to study the deformation characteristics, internal forces and interaction mechanisms of the retaining structures in a multi-bench retaining system and the failure modes of this retaining system. Therefore, a series of model tests of a two-bench retaining system was designed and conducted, and corresponding finite difference simulations were developed to back-analyze the model tests and for further analysis. The tests and numerical results show that the distance between the two rows of retaining piles (bench width) and their embedded lengths can significantly influence the relative movement between the piles; this relative movement determines the horizontal stress distribution in the soil between the two rows of piles (i.e., the bench zone) and thus determines the bending moments in the retaining piles. As the bench width increases, the deformations and bending moments in the retaining piles decrease, while the excavation stability increases. If the second retaining piles are longer than a certain length, they will experience a larger bending moment than the first retaining piles and become the primary retaining structure. In addition, for varying bench widths, the slip surface formation differs, and the failure modes of two-bench retained excavations can be divided into three types: integrated failure, interactive failure and disconnected failure.

Characteristics and prediction methods for tunnel deformations induced by excavations

Zheng, Gang,Du, Yiming,Cheng, Xuesong,Diao, Yu,Deng, Xu,Wang, Fanjun Techno-Press 2017 Geomechanics & engineering Vol.12 No.3

The unloading effect from excavations can cause the deformation of adjacent tunnels, which may seriously influence the operation and safety of those tunnels. However, systematic studies of the deformation characteristics of tunnels located along side excavations are limited, and simplified methods to predict the influence of excavations on tunnels are also rare. In this study, the simulation capability of a finite element method (FEM) considering the small-strain characteristics of soil was verified using a case study. Then, a large number of FEM simulations examining the influence of excavations on adjacent tunnels were conducted. Based on the simulation results, the deformation characteristics of tunnels at different positions and under four deformation modes of the retaining structure were analyzed. The results indicate that the deformation mode of the retaining structure has a significant influence on the deformation of certain tunnels. When the deformation magnitudes of the retaining structures are the same, the influence degree of the excavation on the tunnel increased in this order: from cantilever type to convex type to composite type to kick-in type. In practical projects, the deformation mode of the retaining structure should be optimized according to the tunnel position, and kick-in deformation should be avoided. Furthermore, two methods to predict the influence of excavations on adjacent tunnels are proposed. Design charts, in terms of normalized tunnel deformation contours, can be used to quantitatively estimate the tunnel deformation. The design table of the excavation influence zones can be applied to determine which influence zone the tunnel is located in.

EHMM-CT: An Online Method for Failure Prediction in Cloud Computing Systems

( Weiwei Zheng ),( Zhili Wang ),( Haoqiu Huang ),( Luoming Meng ),( Xuesong Qiu ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.9

The current cloud computing paradigm is still vulnerable to a significant number of system failures. The increasing demand for fault tolerance and resilience in a cost-effective and device-independent manner is a primary reason for creating an effective means to address system dependability and availability concerns. This paper focuses on online failure prediction for cloud computing systems using system runtime data, which is different from traditional tolerance techniques that require an in-depth knowledge of underlying mechanisms. A `failure prediction` approach, based on Cloud Theory (CT) and the Hidden Markov Model (HMM), is proposed that extends the HMM by training with CT. In the approach, the parameter ω is defined as the correlations between various indices and failures, taking into account multiple runtime indices in cloud computing systems. Furthermore, the approach uses multiple dimensions to describe failure prediction in detail by extending parameters of the HMM. The likelihood and membership degree computing algorithms in the CT are used, instead of traditional algorithms in HMM, to reduce computing overhead in the model training phase. Finally, the results from simulations show that the proposed approach provides very accurate results at low computational cost. It can obtain an optimal tradeoff between `failure prediction` performance and computing overhead.

Proteomics Approach to Decipher Novel Genes and Enzymes Characterization of a Bioelectricity-generating and Dye-decolorizing Bacterium Proteus hauseri ZMd44

I-Son Ng,Xuesong Zheng,Bor-Yann Chen,Xiaoqin Chi,Yinghua Lu,Chun-Sheng Chang 한국생물공학회 2013 Biotechnology and Bioprocess Engineering Vol.18 No.1

The first-attempt study employed a proteomics strategy for the identification of abundant proteins from a bioelectricity generation and dye decolorization bacterium Proteus hauseri ZMd44. By using the degenerated primers designed based on the peptide sequences from tandem mass spectroscopy and the whole genomics annotation of the closely associated strain, Proteus penneri ATCC 35198,the genes were successfully obtained for two full-length genes of 543 bp (laccase) and 1,086 bp (Omp F, porin)encoding to 181 amino acids and 362 amino acids,respectively. It explored laccase and NADH dehydrogenase involvement in the oxidation-reduction reaction as well, as porin played an important role in providing channels for related proteins in the accomplishment of electron transportation in P. hauseri. Detailed enzymatic assays indicated that laccase activity of 542.2 U/DCW could be stimulated by 2.5 mM copper induction in LB medium (ca. 293-fold to those without copper induction). Among intracellular proteins, NADH dehydrogenase activity of 257.2 U/mg via mediator riboflavin was in parallel with the decolorizing capability of azo dye Rb160 that only took place in LB medium. From the evaluation of kinetic parameters (Vmax and Km were 0.272 U/min and 0.393 mM with ABTS,0.046 U/min and 43.8 μM with NADH), it is better to decipher the decolorization mechanism of ZMd44 indicating that laccase and NADH dehydrogenase played the most crucial role for azo dye decolorization.

The collapse deformation control of granite residual soil in tunnel surrounding rock: A case study

Zhen Huang,Juncai Huang,Jiabing Zhang,Xuesong Li,Huanyu Zheng,Xiaofei Liu 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.5

Since it is difficult to control tunnel construction in weak and broken surrounding rock, the large deformation of tunnel surrounding rock has always been a great danger to construction safety. In this study, the characteristics of a tunnel collapse deformation and its causal factors are analysed as an example of a large deformation accident in a tunnel with granite residual soil in the surrounding rock. First, a support vector regression algorithm optimized by the genetic annealing algorithm (GASA-SVR) is used to construct a back-analysis model of the surrounding rock mechanical parameters. Then, based on the field measured data, the surrounding rock mechanical parameters of the tunnel are inverted. Finally, the finite element method is used to simulate different surrounding rock deformation control schemes, and the optimal deformation control measures are obtained. The results show that the simulated annealing algorithm (SA) enhances the local search capability of the genetic algorithm (GA) so that the hyperparameter optimization solution of the support vector regression (SVR) is the global optimal solution. The parameters obtained from the inversion of the GASA-SVR model are simulated in PLAXIS3D within 4.0% of the measured values in the field. With the application of optimized support measures at the site, the deformation of the surrounding rock has been effectively controlled.