Experiment research on seismic performance of prestressed steel reinforced high performance concrete beams

Weichen Xue,Feng Yang,Liang Li 국제구조공학회 2009 Steel and Composite Structures, An International J Vol.9 No.2

Two prestressed steel reinforced high performance concrete (SRC) beams, a nonprestressed SRC beam and a counterpart prestressed concrete beam were tested under low reversed cyclic loading to evaluate seismic performance of prestressed SRC beams. The failure modes, deformation restoring capacity, ductility and energy dissipation capacity of the prestressed SRC beams were discussed. Results showed that due to the effect of plastic deformations of steel beams encased in concrete, the three SRC beams exhibited residual deformation ratios ranging between 0.64 and 0.79, which were apparently higher than that of the prestressed concrete beam (0.33). The ductility coefficients of the prestressed SRC beams and the prestressed concrete beam ranged between 4.65 and 4.87, obviously lower than that of nonprestressed SRC beam (9.09), which indicated the steel beams influenced the ductility little while prestressing resulted in an apparent reduction in ductility. The amount of energy dissipated by the prestressed SRC beams was less than that dissipated by the nonprestressed SRC beam but much more than that dissipated by the prestressed concrete beam.

FRChain: A Blockchain-based Flow-Rules-oriented Data Forwarding Security Scheme in SDN

( Weichen Lian ),( Zhaobin Li ),( Chao Guo ),( Zhanzhen Wei ),( Xingyuan Peng ) 한국인터넷정보학회 2021 KSII Transactions on Internet and Information Syst Vol.15 No.1

As the next-generation network architecture, software-defined networking (SDN) has great potential. But how to forward data packets safely is a big challenge today. In SDN, packets are transferred according to flow rules which are made and delivered by the controller. Once flow rules are modified, the packets might be redirected or dropped. According to related research, we believe that the key to forward data flows safely is keeping the consistency of flow rules. However, existing solutions place little emphasis on the safety of flow rules. After summarizing the shortcomings of the existing solutions, we propose FRChain to ensure the security of SDN data forwarding. FRChain is a novel scheme that uses blockchain to secure flow rules in SDN and to detect compromised nodes in the network when the proportion of malicious nodes is less than one-third. The scheme places the flow strategies into blockchain in form of transactions. Once an unmatched flow rule is detected, the system will issue the problem by initiating a vote and possible attacks will be deduced based on the results. To simulate the scheme, we utilize BigchainDB, which has good performance in data processing, to handle transactions. The experimental results show that the scheme is feasible, and the additional overhead for network performance and system performance is less than similar solutions. Overall, FRChain can detect suspicious behaviors and deduce malicious nodes to keep the consistency of flow rules in SDN.

Facile One-Pot Synthesis and Optical Properties of Quinary Wurtzite Cu3ZnInSnS6 Nanocrystals

Dehui Li,Chen Zhang,Yajie Zhang,Weichen Qi,Jinxiang Dong,Jing Yang,Zhidong Qiu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.11

Nearly monodisperse bullet-like Cu3ZnInSnS6 (CZITS) nanocrystals with wurtzite structure were successfully synthesized through optimized noninjection method. The structure, composition, morphology and optical properties of CZITS nanocrystals were characterized by X-ray diffraction, energy dispersive spectrometry, transmission electron microscopy and UV-Vis–NIR absorption. Their suitable bandgap and photoresponsive behavior indicate a high potential application in the field of solar cells. The growth mechanism of the as-synthesized CZITS nanocrystals was preliminarily discussed. It was found that the formation of CZITS could be separated into two steps: nucleation of Cu7S4 and growth of the CZITS main body.

One-Pot Synthesis of Zincblende CuInSe2 Nanocrystals via a Green Solution Reaction Route

Dehui Li,Weichen Qi,Jinglei Xiao,Jing Yang,Yong Wu,Qiao Gao,Shengyong Zhai 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.9

The facile and ecofriendly method for the synthesis of a suitable colloidal nanocrystal ink plays an important role in the field of solar cells. Here, we describe our recent efforts toward this direction by a simple one-pot colloidal method to engineer CuInSe2 (CISe) nanocrystals with cubic zinc-blende (ZB) structure. The suitable band gap value and obvious photoresponse of the as-synthesized CISe nanocrystals indicate their potential application in the field of thin film solar cells. In addition, a possible crystal growth mechanism has been suggested for the formation of ZB CISe.

Interval non-probabilistic time-dependent reliability analysis of boom crane structures

Yang Ruigang,Li Wenzhao,Zhao Guangli,Liu Yuzhen,Jing Weichen 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.2

The reliability of boom crane structure determines the safety and performance of the whole machine. Due to the sample information of uncertain parameter is lacking, nonprobabilistic reliability of boom crane structure under the condition of limited samples is studied. Considering the time dependent deterioration of structure resistance and the load time effect, the time-dependent uncertain parameters of boom structures are comprehensively analyzed. A time-dependent reliability model of boom structures based on interval non-probabilistic is proposed. Based on the theory of interval non-probabilistic time-varying reliability, an engineering example is analyzed by using VC++ programming. The influence of different weight and uncertain parameters on the structure reliability of the boom is analyzed. The results show that the resistance, attenuation coefficient, average resistance and non-probabilistic time-varying reliability indicators of the boom structure attenuate seriously after decades. The conclusion verifies the scientific of the proposed method on the time accumulation effect.

Conceptual configuration and seismic performance of high-rise steel braced frame

Shengfang Qiao,Xiaolei Han,Kemin Zhou,Weichen Li 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.23 No.2

Conceptual configuration and seismic performance of high-rise steel frame-brace structure are studied. First, the topology optimization problem of minimum volume based on truss-like material model under earthquake action is presented, which is solved by full-stress method. Further, conceptual configurations of 20-storey and 40-storey steel frame-brace structure are formed. Next, the 40-storeystructure model is developed in Opensees. Two common configurations are utilized for comparison. Last, seismic performance of 40-storey structure is derived using nonlinear static analysis and nonlinear dynamic analysis. Results indicate that structural lateral stiffness and maximum roof displacement can be improved using brace. Meanwhile seismic damage can also be decreased. Moreover, frame-brace structure using topology optimization is most favorable to enhance lateral stiffness and mitigate seismic damage. Thus, topology optimization is an available way to form initial conceptual configuration in high-rise steel frame-brace structure.

Effect of bending stiffness on the in-plane free vibration characteristics of a cable network

Wei Chen,Zhuojie Zhang,Xiaoxia Zhen,Mingyang Li 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.11

Stay cables of cable-stayed bridges are connected by cross-ties to form a cable network, or the slings of the same suspension points on a suspension bridge are connected by vibration absorbers to form a sling network. As a result, the cable network’s in-plane free vibration characteristics are different from independent, single cables. However, stay cables or slings have certain bending stiffnesses, which directly affect the cable network’s free vibration characteristics. Therefore, to clarify the real dynamic behavior of a cable network and to improve the accuracy of cable network measurements, a multi-node, cross-tied, multilayer beam analytical model that considers the bending stiffness is proposed. The system equilibrium equation is established and the free vibration frequencies and modes of the system are obtained by analytical algorithm. Then, numerical simulations and field experiments, are carried out to verify the analytical results. In addition, parameter analyses with different configurations are performed on a multilayer stay-cable network and on a double-layer sling network to study the influence of bending stiffness on the cable network’s free vibration characteristics with different parameters.

Parameter estimation of partial linear model under monotonicity constraints with censored data

Wei Chen,Xiaojia Li,Dehui Wang,Guohua Shi 한국통계학회 2015 Journal of the Korean Statistical Society Vol.44 No.3

We propose a weighted least square method for estimation in the partial linear model with monotonicity constraints and right-censored data. This method uses the Kaplan–Meier weights to account for censoring and monotone B-splines to approximate the unknown monotone function.Weshow that the proposed estimator of regression coefficients is rootn consistent and asymptotically normal under appropriate assumptions. One advantage is that our method can be easily computed using existing software. A simulation study is conducted to evaluate the finite sample performance of the proposed method.