Feasibility study of improved particle swarm optimization in kriging metamodel based structural model updating

Yun-Lai Zhou,Shiqiang Qin,Jia Hu,Yazhou Zhang,Juntao Kang 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.70 No.5

This study proposed an improved particle swarm optimization (IPSO) method ensemble with kriging model for model updating. By introducing genetic algorithm (GA) and grouping strategy together with elite selection into standard particle optimization (PSO), the IPSO is obtained. Kriging metamodel serves for predicting the structural responses to avoid complex computation via finite element model. The combination of IPSO and kriging model shall provide more accurate searching results and obtain global optimal solution for model updating compared with the PSO, Simulate Annealing PSO (SimuAPSO), BreedPSO and PSOGA. A plane truss structure and ASCE Benchmark frame structure are adopted to verify the proposed approach. The results indicated that the hybrid of kriging model and IPSO could serve for model updating effectively and efficiently. The updating results further illustrated that IPSO can provide superior convergent solutions compared with PSO, SimuAPSO, BreedPSO and PSOGA.

DEPTOR Expression Negatively Correlates with mTORC1 Activity and Tumor Progression in Colorectal Cancer

Lai, Er-Yong,Chen, Zhen-Guo,Zhou, Xuan,Fan, Xiao-Rong,Wang, Hua,Lai, Ping-Lin,Su, Yong-Chun,Zhang, Bai-Yu,Bai, Xiao-Chun,Li, Yun-Feng Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.11

The mammalian target of rapamycin (mTOR) signaling pathway is upregulated in the pathogenesis of many cancers, including colorectal cancer (CRC). DEPTOR is an mTOR inhibitor whose expression is negatively regulated by mTOR. However, the role of DEPTOR in the development of CRC is not known. The aim of this study was to investigate the expression of DEPTOR and mTORC1 activity (P-S6) in a subset of CRC patients and determine their relation to tumor differentiation, invasion, nodal metastasis and disease-free survival. Here, Immunohistochemical expression of P-S6 (S235/236) and DEPTOR were evaluated in 1.5 mm tumor cores from 90 CRC patients and in 90 samples of adjacent normal mucosa by tissue microarray. The expression of P-S6 (S235/236) was upregulated in CRC, with the positive rate of P-S6 (S235/236) in CRC (63.3%) significantly higher than that in control tissues (36.7%, 30%) (p<0.05). P-S6 (S235/236) also correlated with high tumor histologic grade (p=0.002), and positive nodal metastasis (p=0.002). In contrast, the expression level of DEPTOR was correlated with low tumor histological grade (p=0.006), and negative nodal metastasis (p=0.001). Interestingly, P-S6 (S235/236) expression showed a significant negative association with the expression of DEPTOR in CRC (p=0.011, R= -0.279). However, upregulation of P-S6 (S235/236) (p=0.693) and downregulation of DEPTOR (p=0.331) in CRC were not significantly associated with overall survival. Thus, we conclude that expression of DEPTOR negatively correlates with mTORC1 activity and tumor progression in CRC. DEPTOR is a potential marker for prognostic evaluation and a target for the treatment of CRC.

Numerical modelling of bottom-hole rock in underbalanced drilling using thermo-poroelastoplasticity model

Weiji Liu,Yun-Lai Zhou,Xiaohua Zhu,Xiannan Meng,Mei Liu,Magd Abdel Wahab 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.69 No.5

Stress analysis of bottom-hole rock has to be considered with much care to further understand rock fragmentation mechanism and high penetration rate. This original study establishes a fully coupled simulation model and explores the effects of overburden pressure, horizontal in-situ stresses, drilling mud pressure, pore pressure and temperature on the stress distribution in bottom-hole rock. The research finds that in air drilling, as the well depth increases, the more easily the bottom-hole rock is to be broken. Moreover, the mud pressure has a great effect on the bottom-hole rock. The bigger the mud pressure is, the more difficult to break the bottom-hole rock is. Furthermore, the maximum principal stress of the bottom-hole increases as the mud pressure, well depth and temperature difference increase. The bottom-hole rock can be divided into three main regions according to the stress state, namely a) three directions tensile area, b) two directions compression areas and c) three directions compression area, which are classified as a) easy, b) normal and c) hard, respectively, for the corresponding fragmentation degree of difficulty. The main contribution of this paper is that it presents for the first time a thorough study of the effect of related factors, including stress distribution and temperature, on the bottom-hole rock fracture rather than the well wall, using a thermo-poroelastoplasticity model.

Footbridge Serviceability Analysis: From System Identification to Tuned Mass Damper Implementation

Shiqiang Qin,Yun-Lai Zhou,Juntao Kang 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.2

Footbridges usually suffer from vibrations induced by the actions of pedestrians, which calls for various control measures to improve the serviceability. This study described the dynamic analysis and Tuned Mass Damper (TMD) implementation for a singlepylon cable-stayed footbridge scaled model, aimed at providing an experimental case study regarding of vibration control design of slender structures. A scaled model for the real footbridge was designed based on similarity principles. Then, the dynamic behavior of the footbridge was assessed by ambient vibration tests. The natural frequencies and mode shapes were identified from operational vibration measurements by covariance-driven stochastic subspace identification algorithm. The frequency of first vertical bending modes is 2.10 Hz, falling into the human walking frequency range [1.6, 2.4] Hz. Therefore, the footbridge needs vibration control to improve its serviceability. Finally, a self-made TMD using lead, spring and oil buffer was implemented on the scaled model of the footbridge. The laboratory forced vibration test was employed to illustrate the effectiveness of the TMD. By installing TMD, the acceleration response at mid-span of the footbridge was remarkably reduced. The study could provide meaningful reference for vibration control design of the full-scale footbridge.

Model Updating in Complex Bridge Structures using Kriging Model Ensemble with Genetic Algorithm

Shiqiang Qin,Yun-Lai Zhou,Hongyou Cao,Magd Abdel Wahab 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.9

Computational cost reduction and the best solution seeking are frequently encountered during model updating for complex structures. In this study, a hybrid algorithm using kriging model and genetic algorithms (GAs) is proposed for updating the Finite Element (FE) model of complex bridge structures employing both static and dynamic experimental measurements. The kriging model is first established to approximate the implicit relationship between structural parameters and responses, serving as a surrogate model for complex FE model when deriving analytical responses. An objective function is later defined based on the residual between analytical response values and experimental measured ones. GAs are finally employed to find the best solution by searching on the whole design space of updating parameters selected based on a sensitivity analysis. To verify the proposed algorithm, Caiyuanba Yangtze River Bridge, a double decked of roadway and light railway bridge with a main span of 420 m is used. Both frequencies and displacements predicted by the updated model are more close to experimental measured ones. The results show that the kriging surrogate model has good accuracy in predicting response and can be used as a surrogate model to reduce computational cost, and GAs provide a higher chance to obtain global best solution.

Form- finding analysis of suspension bridges using an explicit Iterative approach

Hongyou Cao,Yun-Lai Zhou,Zhijun Chen,Magd Abdel Wahab 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.62 No.1

This paper presents an explicit analytical iteration method for form-finding analysis of suspension bridges. By extending the conventional analytical form-finding method predicated on the elastic catenary theory, two nonlinear governing equations are derived for calculating the accurate unstrained lengths of the entire cable systems both the main cable and the hangers. And for the gradient-based iteration method, the derivation of explicit calculation for the Jacobian matrix while solving the nonlinear governing equation enhances the computational efficiency. The results from sensitivity analysis show well performance of the explicit Jacobian matrix compared with the traditional finite difference method. According to two numerical examples of long span suspension bridges studied, the proposed method is also compared with those reported approaches or the fundamental criterions in suspension bridge structural analysis, which eventually confirms the accuracy and efficiency of the proposed approach.

Bonded-cluster simulation of tool-rock interaction using advanced discrete element method

Weiji Liu,Xiaohua Zhu,Yun-Lai Zhou,Tao Li,Xiangning Zhang 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.72 No.4

The understanding of tool-rock interaction mechanism is of high essence for improving the rock breaking efficiency and optimizing the drilling parameters in mechanical rock breaking. In this study, the tool-rock interaction models of indentation and cutting are carried out by employing the discrete element method (DEM) to examine the rock failure modes of various brittleness rocks and critical indentation and cutting depths of the ductile to brittle failure mode transition. The results show that the cluster size and inter-cluster to intra-cluster bond strength ratio are the key factors which influence the UCS magnitude and the UCS to BTS ratio. The UCS to BTS strength ratio can be increased to a more realistic value using clustered rock model so that the characteristics of real rocks can be better represented. The critical indentation and cutting depth decrease with the brittleness of rock increases and the decreasing rate reduces dramatically against the brittleness value. This effort may lead to a better understanding of rock breaking mechanisms in mechanical excavation, and may contribute to the improvement in the design of rock excavation machines and the related parameters determination.

Noise and Vibration Mitigation Performance of Damping Pad under CRTS-III Ballastless Track in High Speed Rail Viaduct

Linya Liu,Rui Song,Yun-Lai Zhou,Jialiang Qin 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.8

This study proposes a frequency domain vehicle-track coupling model for the CRTS (China railways track system)-III type damping track system based on the two-dimensional vehicle-track-viaduct coupling model, and utilizes dynamic compliance method to determine the dynamic compliance for the vehicle and track systems. The accelerations for the viaduct are hereinafter obtained and are compared between CRTS-III damping track system and conventional CRTS-III track system, and the structure-borne noises for near field and far field of the viaduct are assessed with finite element method (FEM). The acoustic contribution rates for the substructures of the viaduct to the near-field and far-field noises are analyzed. The results reveal that in comparison with the conventional CRTS-III system, the CRTS-III damping track system can mitigate the viaduct acceleration peak with 69.9%, and mitigate the average acceleration with 60.4%. The near field and far field noise measurement points are captured for the CRTS-III damping track system, the sound pressure levels decline by 8.15 dB and 8.36 dB, respectively. The acoustic contribution rates for the viaduct top plate reach 65.28% and 68.30%, respectively. The viaduct top plate thus becomes the major noise source and the damping track system can effectively mitigate the structure-borne noise of the viaduct.

The ROP mechanism study in hard formation drilling using local impact method

Weiji Liu,Xiaohua Zhu,Yun-Lai Zhou,Liu Mei,Xiannan Meng,Cheng Jiang 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.68 No.1

The low rate of penetration and short lifetime of drilling bit served as the most common problems encountered in hard formation drilling, thus leading to severe restriction of drilling efficiency in oil and gas reservoir. This study developed a new local impact drilling method to enhance hard formation drilling efficiency. The limitation length formulas of radial/lateral cracks under static indentation and dynamic impact are derived based on the experimental research of Marshall D.B considering the mud column pressure and confining pressure. The local impact rock breaking simulation model is conducted to investigate its ROP raising effect. The results demonstrate that the length of radial/lateral cracks will increase as the decrease of mud pressure and confining pressure, and the local impact can result in a damage zone round the impact crater which helps the rock cutting, thus leading to the ROP increase. The numerical results also demonstrate the advantages of local impact method for raising ROP and the vibration reduction of bit in hard formation drilling. This study has shown that the local impact method can help raising the ROP and vibration reduction of bit, and it may be applied in drilling engineering.

Structural noise mitigation for viaduct box girder using acoustic modal contribution analysis

Liu Linya,Jialiang Qin,Yun-Lai Zhou,Rui Xi,Siyuan Peng 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.72 No.4

In high-speed railway (HSR) system, the structure-borne noise inside viaduct at low frequency has been extensively investigated for its mitigation as a research hotspot owing to its harm to the nearby residents. This study proposed a novel acoustic optimization method for declining the structure-borne noise in viaduct-like structures by separating the acoustic contribution of each structural component in the measured acoustic field. The structural vibration and related acoustic sourcing, propagation, and radiation characteristics for the viaduct box girder under passing vehicle loading are studied by incorporating Finite Element Method (FEM) with Modal Acoustic Vector (MAV) analysis. Based on the Modal Acoustic Transfer Vector (MATV), the structural vibration mode that contributes maximum to the structure-borne noise shall be hereinafter filtered for the acoustic radiation. With vibration mode shapes, the locations of maximum amplitudes for being ribbed to mitigate the structure-borne noise are then obtained, and the structure-borne noise mitigation performance shall be eventually analyzed regarding to the ribbing conduction. The results demonstrate that the structural vibration and structure-borne noise of the viaduct box girder mainly occupy both in the range within 100 Hz, and the dominant frequency bands both are [31.5, 80] Hz. The peak frequency for the structureborne noise of the viaduct box girder is mainly caused by 16th and 62th vibration modes; these two mode shapes mainly reflect the local vibration of the wing plate and top plate. By introducing web plate at the maximum amplitude of main mode shapes that contribute most to the acoustic modal contribution factors, the acoustic pressure peaks at the field-testing points are hereinafter obviously declined, this implies that the structure-borne noise mitigation performance is relatively promising for the viaduct.