Semi-active control on long-span reticulated steel structures using MR dampers under multi-dimensional earthquake excitations

Zhou, Zhen,Meng, Shao-Ping,Wu, Jing,Zhao, Yong Techno-Press 2012 Smart Structures and Systems, An International Jou Vol.10 No.6

This paper focuses on the vibration control of long-span reticulated steel structures under multi-dimensional earthquake excitation. The control system and strategy are constructed based on Magneto-Rheological (MR) dampers. The LQR and Hrovat controlling algorithm is adopted to determine optimal MR damping force, while the modified Bingham model (MBM) and inverse neural network (INN) is proposed to solve the real-time controlling current. Three typical long-span reticulated structural systems are detailedly analyzed, including the double-layer cylindrical reticulated shell, single-layer spherical reticulated shell, and cable suspended arch-truss structure. Results show that the proposed control strategy can reduce the displacement and acceleration effectively for three typical structural systems. The displacement control effect under the earthquake excitation with different PGA is similar, while for the cable suspended arch-truss, the acceleration control effect increase distinctly with the earthquake excitation intensity. Moreover, for the cable suspended arch-truss, the strand stress variation can also be effectively reduced by the MR dampers, which is very important for this kind of structure to ensure that the cable would not be destroyed or relaxed.

Simulation and performance evaluation of the anoxic/anaerobic/aerobic process for biological nutrient removal

Zhen Zhou,Zhichao Wu,Zhiwei Wang,Shujuan Tang,Guowei Gu,Luochun Wang,Yingjun Wang,Zhiling Xin 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.5

As a modified configuration of the conventional anaerobic/anoxic/aerobic (AAO) process, a novel anoxic/anaerobic/aerobic (Reversed AAO, RAAO) process has been extensively applied in domestic wastewater treatment plants (WWTP). In this study, the Activated Sludge Model No. 2d (ASM2d) and a secondary clarifier model were calibrated and applied to simulate a pilot-scale RAAO test and evaluate the operational performance of the RAAO process. For calibration of the biological model ASM2d, only four kinetic parameters were adjusted to accurately simulate in-process variations of ammonium, nitrate and phosphate. Simulation results by the calibrated model demonstrated that phosphorus accumulating organisms (PAO) in the RAAO process (0.243 gP·(gCOD)^−1) contains less poly-phosphate than the AAO process (0.266 gP·(gCOD)^−1). With the increasing mixed liquor recirculation ratio in the RAAO process,the fraction of heterotrophic biomass and autotrophic biomass both increased, whereas the PAO decreased owing to adverse effects of electron acceptors on phosphorus release and poly-hydroxy-alkanoates synthesis.

DTSTM: Dynamic Tree Style Trust Measurement Model for Cloud Computing

( Zhen-ji Zhou ),( Li-fa Wu ),( Zheng Hong ),( Ming-fei Xu ),( Fan Pan ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.1

In cloud computing infrastructure, current virtual machine trust measurement methods have many shortcomings in dynamism, security and concurrency. In this paper, we present a new method to measure the trust of virtual machine. Firstly, we propose “behavior trace” to describe the state of virtual machine. Behavior trace is a sequence of behaviors. The measurement of behavior trace is conducted on the basis of anticipated trusted behavior, which not only ensures security of the virtual machine during runtime stage but also reduces complexity of the trust measurement. Based on the behavior trace, we present a Dynamic Tree Style Trust Measurement Model (DTSTM). In this model, the measurement of system domain and user domain is separated, which enhances the extensibility, security and concurrency of the measurement. Finally, based on System Call Interceptor (SCI) and Virtual Machine Introspection (VMI) technology, we implement a DTSTM prototype system for virtual machine trust measurement. Experimental results demonstrate that the system can effectively verify the trust of virtual machine and requires a relatively low performance overhead.

Two collinear Mode-I cracks in piezoelectric/piezomagnetic materials

Zhou, Zhen-Gong,Wang, Jia-Zhi,Wu, Lin-Zhi Techno-Press 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.29 No.1

In this paper, the behavior of two collinear Mode-I cracks in piezoelectric/piezomagnetic materials subjected to a uniform tension loading was investigated by the generalized Almansi's theorem. Through the Fourier transform, the problem can be solved with the help of two pairs of triple integral equations, in which the unknown variables were the jumps of displacements across the crack surfaces. To solve the triple integral equations, the jumps of displacements across the crack surfaces were directly expanded as a series of Jacobi polynomials to obtain the relations among the electric displacement intensity factors, the magnetic flux intensity factors and the stress intensity factors at the crack tips. The interaction of two collinear cracks was also discussed in the present paper.

A Novel Form Analysis Method Considering Pretension Process for Suspen-dome Structures

Zhen Zhou,Yu-long Feng,Shao-ping Meng,Jing Wu 대한토목학회 2014 KSCE JOURNAL OF CIVIL ENGINEERING Vol.18 No.5

Suspen-dome is a kind of new prestressed space grid structure which is formed by combing a single-layer reticulated shell andtensegrity system. For the existence of lower flexible cable-strut system, form analysis is crucial for the mechanical performance ofsuspen-domes. This paper develops a novel form analysis method considering the influence of pretension process for suspen-domestructures. Some definitions of form analysis for suspen-dome structures are first expounded. Then an iterative method is presentedfor form analysis, and a sequential analysis method is proposed for pretension process simulation. By combining these two methods,a form analysis method considering pretension process is constructed for suspen-dome structures. Two examples are employed toverify the proposed method. Numerical example results show that both the error of nodal coordinates and cable forces can stablyconverge to set tolerances. According to a scheduled pretension scheme, form analysis results can accurately achieve the expectedinitial state. Engineering example results show that without considering the influence of pretension process, the form analysis wouldbe error and the final state after all cables tensioned deviates greatly from the expected initial state. However, this can be achievedaccurately through the proposed method in this paper.

The nonlocal theory solution for two collinear cracks in functionally graded materials subjected to the harmonic elastic anti-plane shear waves

Zhou, Zhen-Gong,Wang, Biao Techno-Press 2006 Structural Engineering and Mechanics, An Int'l Jou Vol.23 No.1

In this paper, the scattering of harmonic elastic anti-plane shear waves by two collinear cracks in functionally graded materials is investigated by means of nonlocal theory. The traditional concepts of the non-local theory are extended to solve the fracture problem of functionally graded materials. To overcome the mathematical difficulties, a one-dimensional non-local kernel is used instead of a two-dimensional one for the anti-plane dynamic problem to obtain the stress field near the crack tips. To make the analysis tractable, it is assumed that the shear modulus and the material density vary exponentially with coordinate vertical to the crack. By use of the Fourier transform, the problem can be solved with the help of a pair of triple integral equations, in which the unknown variable is the displacement on the crack surfaces. To solve the triple integral equations, the displacement on the crack surfaces is expanded in a series of Jacobi polynomials. Unlike the classical elasticity solutions, it is found that no stress singularities are present at crack tips.

Comparative Study between ZOOMit and Conventional Intravoxel Incoherent Motion MRI for Assessing Parotid Gland Abnormalities in Patients with Early- or Mid-Stage Sjögren’s Syndrome

Zhou Qing-Qing,Zhang Wei,Yu Yu-Sheng,Li Hong-Yan,Wei Liang,Li Xue-Song,He Zhen-Zhen,Zhang Hong 대한영상의학회 2022 Korean Journal of Radiology Vol.23 No.4

Objective: To compare the reproducibility and performance of quantitative metrics between ZOOMit and conventional intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) in the diagnosis of early- and mid-stage Sjögren’s syndrome (SS). Materials and Methods: Twenty-two patients (mean age ± standard deviation, 52.0 ± 10.8 years; male:female, 2:20) with early- or mid-stage SS and 20 healthy controls (46.9 ± 14.6 years; male:female, 7:13) were prospectively enrolled in our study. ZOOMit IVIM and conventional IVIM MRI were performed simultaneously in all individuals using a 3T scanner. Quantitative IVIM parameters - including tissue diffusivity (D), pseudodiffusion coefficient (D*), and perfusion fraction (f) - inter- and intra-observer reproducibility in measuring these parameters, and their ability to distinguish patients with SS from healthy individuals were assessed and compared between ZOOMit IVIM and conventional IVIM methods, appropriately. MR gland nodular grade (MRG) was also examined. Results: Inter- and intra-observer reproducibility was better with ZOOMit imaging than with conventional IVIM imaging (ZOOMit vs. conventional, intraclass correlation coefficient of 0.897–0.941 vs. 0.667–0.782 for inter-observer reproducibility and 0.891–0.968 vs. 0.814–0.853 for intra-observer reproducibility). Significant differences in ZOOMit f, ZOOMit D*, conventional D*, and MRG between patients with SS and healthy individuals (all p < 0.05) were observed. ZOOMit D* outperformed conventional D* in diagnosing early- and mid-stage SS (area under receiver operating curve, 0.867 and 0.658, respectively; p = 0.002). The combination of ZOOMit D*, MRG, and ZOOMit f as a new diagnostic index for SS, increased diagnostic area under the curve to 0.961, which was higher than that of any single parameter (all p < 0.01). Conclusion: Considering its better reproducibility and performance, ZOOMit IVIM may be preferred over conventional IVIM MRI, and may subsequently improve the ability to diagnose early- and mid-stage SS.

Semi-active control on long-span reticulated steel structures using MR dampers under multi-dimensional earthquake excitations

Zhen Zhou,Shao-ping Meng,Jing Wu,Yong Zhao 국제구조공학회 2012 Smart Structures and Systems, An International Jou Vol.10 No.6

This paper focuses on the vibration control of long-span reticulated steel structures under multidimensional earthquake excitation. The control system and strategy are constructed based on Magneto- Rheological (MR) dampers. The LQR and Hrovat controlling algorithm is adopted to determine optimal MR damping force, while the modified Bingham model (MBM) and inverse neural network (INN) is proposed to solve the real-time controlling current. Three typical long-span reticulated structural systems are detailedly analyzed, including the double-layer cylindrical reticulated shell, single-layer spherical reticulated shell, and cable suspended arch-truss structure. Results show that the proposed control strategy can reduce the displacement and acceleration effectively for three typical structural systems. The displacement control effect under the earthquake excitation with different PGA is similar, while for the cable suspended arch-truss, the acceleration control effect increase distinctly with the earthquake excitation intensity. Moreover, for the cable suspended arch-truss, the strand stress variation can also be effectively reduced by the MR dampers, which is very important for this kind of structure to ensure that the cable would not be destroyed or relaxed.

Investigation of the behavior of a crack between two half-planes of functionally graded materials by using the Schmidt method

Zhou, Zhen-Gong,Wang, Biao,Wu, Lin-Zhi Techno-Press 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.19 No.4

In this paper, the behavior of a crack between two half-planes of functionally graded materials subjected to arbitrary tractions is resolved using a somewhat different approach, named the Schmidt method. To make the analysis tractable, it is assumed that the Poisson's ratios of the mediums are constants and the shear modulus vary exponentially with coordinate parallel to the crack. By use of the Fourier transform, the problem can be solved with the help of two pairs of dual integral equations in which the unknown variables are the jumps of the displacements across the crack surfaces. To solve the dual integral equations, the jumps of the displacements across the crack surfaces are expanded in a series of Jacobi polynomials. This process is quite different from those adopted in previous works. Numerical examples are provided to show the effect of the crack length and the parameters describing the functionally graded materials upon the stress intensity factor of the crack. It can be shown that the results of the present paper are the same as ones of the same problem that was solved by the singular integral equation method. As a special case, when the material properties are not continuous through the crack line, an approximate solution of the interface crack problem is also given under the assumption that the effect of the crack surface interference very near the crack tips is negligible. It is found that the stress singularities of the present interface crack solution are the same as ones of the ordinary crack in homogenous materials.

Minimizing Average Startup Latency of VMs by Clustering-based Template Caching Scheme in an IaaS System

Zhen Zhou,Shuyu Chen,Mingwei Lin,Guiping Wang,Qian Yang 보안공학연구지원센터(IJUNESST) 2013 International Journal of u- and e- Service, Scienc Vol.6 No.6