Progressive Collapse Analysis of Large-span Reticulated Domes

Qinghua Han,Mingjie Liu,Yan Lu,Chenxu Wang 한국강구조학회 2015 International Journal of Steel Structures Vol.15 No.2

The paper presents the progressive collapse analysis of large-span reticulated domes based on Alternate path (AP) method. Nonlinear buckling analysis is conducted on a large span roof with two different structural layouts. The results show that although large-span single-layer reticulated dome has a certain redundancy. When 10 key elements or 3 key nodes were removed, the single-layer reticulated dome under the service load would cause progressive collapse. Therefore the protection of key nodes of this structure should be strengthened. However, the redundancy of large-span double-layer reticulated dome is 7 to 13 times that of single-layer reticulated dome. When 10 key elements or 3 key nodes were removed, the double-layer reticulated dome under the service load would not cause progressive collapse. Hence, the resistance to progressive collapse of large-span double-layer reticulated dome is better than that of large-span single-layer reticulated dome.

Cyclic Response and Constitutive Model Study of G20Mn5QT Cast Steel

Qinghua Han,Qianwen Huang,Yan Lu 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.4

A series of cyclic loading tests of G20Mn5QT cast steel are carried out at the strain ratio of − 1. The results of tests show that the G20Mn5QT cast steel has the similar tendency in cyclic softening with diff erent constant strain amplitude. A slight strain softening is observed, and then the stress states keep steady during the remaining cycles. A new damage variable is proposed considering the eff ects of strength degeneration within two inner variables which are the maximum equivalent plastic strain and the equivalent plastic strain increment. The damage variable provides better insight into the multiaxial cyclic loading and gives a reasonable prediction of failure under the loading history of constant strain amplitude. The proposed damage variable is further introduced in the cyclic constitutive model by the user subroutine interfaces VUMAT by the software ABAQUS. The relationships between the equivalent plastic strain and the damage variable, Young’s modulus and yield strength are fi nally put forward as it is expedient to get the equivalent plastic strain in the numerical analysis.

Experimental research on load-bearing capacity of cast steel joints for beam-to-column

Qinghua Han,Mingjie Liu,Yan Lu 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.56 No.1

The load transfer mechanism and load-bearing capacity of cast steel joints for H-shaped beam to square tube column connection are studied based on the deformation compatibility theory. Then the monotonic tensile experiments are conducted for 12 specimens about the cast steel joints for H-shaped beam to square tube column connection. The findings are that the tensile bearing capacity of the cast steel joints for beam-column connection depends on the ring of cast steel stiffener. The tensile fracture happens at the ring of the cast steel stiffener when the joint fails. The thickness of square tube column has little influence on the bearing capacity of the joint. The square tube column buckles while the joint without concrete filled, but the strength failure happens for the joint with concrete filled column. And the length of welding connection between square tube column and cast steel stiffener has little influence on the load-bearing capacity of the cast steel joint. Finally it is shown that the load-bearing capacity of the joints for H-shaped beam to concrete filled square tube column connection is larger than that of the joints for H-shaped beam to square tube column connection by 10% to 15%.

A Novel Low-cost Thin-film Flat Plate Photobioreactor for Microalgae Cultivation

Chenghu Yan,Qinghua Zhang,Shengzhang Xue,Zhongliang Sun,Xia Wu,Zhihui Wang,Yunming Lu,Wei Cong 한국생물공학회 2016 Biotechnology and Bioprocess Engineering Vol.21 No.1

In this study, a novel thin-film flat plate photobioreactor (FPPBR) mounted with baffles and a 61.2 m2 (2,000 L) photobioreactor system based on the FPPBR were developed. The flow of the fluid in the thinfilm photobioreactor was investigated by means of computational fluid dynamics (CFD). The cultivation of Chlorella sp. and Scenedesmus dimorphus in the thin-film FPPBR was carried out outdoors. The results showed that the flow of culture medium in different channels was uniform. In outdoor cultivation, the biomass productivity in the FPPBR with baffles was 25.2% higher than that in the FPPBR without baffles. In the pilot-scale FPPBR system, the maximum area productivity of Scenedesmus dimorphus reached 21.9 g/m2/day. When the service time of the photobioreactor was 1 and 3 years, the capital cost of the photobioreactor was 4.72 and 2.45 $ kgalgae, respectively. The results demonstrated that the thin-film FPPBR was cost effective, and it has the potential to be used for mass cultivation of microalgae.

Electronic Circuit Optimization Design Algorithm based on Adaptive Culture Search

Xuesong Yan,Qinghua Wu,Chengyu Hu,Hong Yao,Hanmin Liu 보안공학연구지원센터 2013 International Journal of Control and Automation Vol.6 No.4

Robot Path Planning based on Swarm Intelligence

Xuesong Yan,Qinghua Wu,Chengyu Hu,Hong Yao,Yuanyuan Fan,Qingzhong Liang,Chao Liu 보안공학연구지원센터 2014 International Journal of Control and Automation Vol.7 No.7

Experimental Study of Horizontal Gas-liquid Two-phase Flow in Two Medium-diameter Pipes and Prediction of Pressure Drop through BP Neural Networks

Wang Qinghua,Zou Honglan,Luo Wei,Yang Junzheng,Wen Xiaohong,Wang Yan 한국유체기계학회 2018 International journal of fluid machinery and syste Vol.11 No.3

Horizontal gas-liquid two-phase flow is of crucial importance in oil-gas storage and transportation. In view of previous researches with the lack of horizontal gas-liquid two-phase flow in medium-diameter pipes (60-75 ㎜), experiments were conducted in DN 60 and DN75 at medium-high liquid velocity (50-250 m3/d) and high gas-liquid ratio (20-500 m3/m3). Comparison between flow patterns maps in DN60 and DN75 and the Taitel-Dukler model showed that only flow patterns map in DN60 agreed well. On the basis of experimental data analysis, variation laws of liquid holdup and pressure drop were determined. Besides, this paper developed a method to predict liquid holdup and pressure drop through BP neural networks. Results proved the capability of BP neural networks. The further validation can be made in practical applications.

Combining Adaptive Filtering and IF Flows to Detect DDoS Attacks within a Router

( Ruoyu Yan ),( Qinghua Zheng ),( Haifei Li ) 한국인터넷정보학회 2010 KSII Transactions on Internet and Information Syst Vol.4 No.3

Traffic matrix-based anomaly detection and DDoS attacks detection in networks are research focus in the network security and traffic measurement community. In this paper, firstly, a new type of unidirectional flow called IF flow is proposed. Merits and features of IF flows are analyzed in detail and then two efficient methods are introduced in our DDoS attacks detection and evaluation scheme. The first method uses residual variance ratio to detect DDoS attacks after Recursive Least Square (RLS) filter is applied to predict IF flows. The second method uses generalized likelihood ratio (GLR) statistical test to detect DDoS attacks after a Kalman filter is applied to estimate IF flows. Based on the two complementary methods, an evaluation formula is proposed to assess the seriousness of current DDoS attacks on router ports. Furthermore, the sensitivity of three types of traffic (IF flow, input link and output link) to DDoS attacks is analyzed and compared. Experiments show that IF flow has more power to expose anomaly than the other two types of traffic. Finally, two proposed methods are compared in terms of detection rate, processing speed, etc., and also compared in detail with Principal Component Analysis (PCA) and Cumulative Sum (CUSUM) methods. The results demonstrate that adaptive filter methods have higher detection rate, lower false alarm rate and smaller detection lag time.

Microstructure Evolution and Mechanical Performances of SiCf Reinforced (Al3Ti + Al3Ni)-Based Metallic–Intermetallic Laminate Composite

Yuqiang Han,Qinghua Que,Ran Cheng,Ran Cheng,Chunfa Lin,Wenqing Han,Enhao Wang,Junyi Zhu,Haoran Yan 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.10

In present work, a novel SiCfreinforced (Al3Ti + Al3Ni)-based metallic–intermetallic laminate (Ti–(Al3Ti + Al3Ni)/SiCf-MIL) composite without centerline defect was prepared using Ti, Al foils, NiTi wires and SiC fibers by vacuum hot pressingsintering method. Electron backscatter diffraction was employed to characterize the microstructure and phase constituents ofTi–(Al3Ti + Al3Ni)/SiCf-MIL composite during various stages of preparation process. The elimination mechanism of intermetalliccenterline was discussed. Besides, quasi-static compressive performance and fracture toughness of the synthesizedcomposite were investigated. The experimental results indicated that as reaction time increasing, the NiTi/Al interfacialreaction occurred prior to the Ti/Al interfacial reaction to form an Al3Ti/Al3Ni zone. Then, the oxides gathered at the frontof Ti/Al interfacial reaction layer were dispersed in the intermetallic layer rather than being pushed together to generate thecenterline due to the Al3Ti/Al3Ni zone. After reaction, there were no residual NiTi phases and intermetallic layers mainlyconsisting of Al3Tiand Al3Niphases were obtained in this composite. In addition, high angle grain boundaries in Al3Tigrains occupied a large proportion, conversely, low angle grain boundaries dominated in Al3Nigrains. Furthermore, stressconcentration appears at the interface between layers instead of along the middle plane of intermetallic layer. Moreover,both compressive strength and fracture toughness of the composite are superior in comparison with SiCfreinforced Ti–Al3Timetallic–intermetallic laminate composite (Ti–Al3Ti/SiCf-MIL) ascribed to the elimination of centerline.

A New Micromechanical Criterion for Ductile Fracture of G20Mn5QT Cast Steels Under Shear Stress

Yue Yin,Mengfei Li,Qinghua Han,Yan Lu,Jinghan Bai 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.5

A new micromechanical criterion was proposed for ductile fracture caused by shear in low stress triaxiality regions. The infl uences of both the stress triaxiality and the Lode parameter were reasonably considered. The formula of the critical plastic strain for ductile fracture by shear was deduced based on the idea that the evolution of microvoids in materials under shear stresses is a successive procedure of nucleation, growth, elongation and collapse. Six shear specimens of G20Mn5QT cast steels were tested under monotonic tension. Three confi gurations of these specimens provided diff erent combinations of the stress triaxiality and the Lode parameter. The critical void compression ratio for the void collapse was determined based on unit cell analysis and the shape of the dimples on the fracture surfaces of the test specimens. Parameters in the proposed criterion were then calibrated for G20Mn5QT cast steels based on tests and complementary fi nite element analysis of the shear specimens. Finally, diff erent fracture mechanisms of G20Mn5QT cast steels were discussed.