Component based moment-rotation model of composite beam blind bolted to CFDST column joint

Lei Guo,Jingfeng Wang,Wanqian Wang,Zhaodong Ding 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.38 No.5

This paper aims to explore the mechanical behavior and moment-rotation model of blind bolted joints between concrete-filled double skin steel tubular columns and steel-concrete composite beams. For this type of joint, the inner tube and sandwiched concrete were additionally identified as basic components compared with CFST blind bolted joint. A modified moment-rotation model for this type of connection was developed, of which the compatibility condition and mechanical equilibrium were employed to determine the internal forces of basic components and neutral axis. Following this, load transfer mechanism among the inner tube, sandwiched concrete and outer tube was discussed to assert the action area of the components. Subsequently, assembly processes of basic coefficients in terms of their stiffness and resistances based on the component method by simplifying them as assemblages of springs in series or in parallel. Finally, an experimental investigation on four substructure joints with CFDST columns for validation purposes was carried out to capture the connection details. The predicted results derived from the mechanical models coincided well with the experimental results. It is demonstrated that the proposed mechanical model is capable of evaluating the complete moment-rotation relationships of blind bolted CFDST column composite connections.

Experimental and theoretical studies of benzalkonium chloride as an inhibitor for carbon steel corrosion in sulfuric acid

Lei Guo,Shanhong Zhu,Shengtao Zhang 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.24 No.-

The effect of benzalkonium chloride (BKC) on the corrosion of carbon steel in H2SO4 media has been examined by electrochemical impedance spectroscopy (EIS), polarization, weight loss, and scanning electron microscopy (SEM) methods. The results showed that the corrosion inhibition efficiency of BKC was excellent. Potentiodynamic polarization study showed that the BKC was a mixed-type inhibitor. DFT calculations were used to gain insight into the structural and electronic properties in relation to the inhibition efficiency. Molecular dynamics (MD) simulations demonstrate that chloride ion plays a significant role in the inhibition mechanism.

Enhanced Dynamic Segment Protection in WDM Optical Networks under Reliability Constraints

Lei Guo,Jin Cao,Hongfang Yu,Lemin Li 한국전자통신연구원 2006 ETRI Journal Vol.28 No.1

In this letter, we study the protection problem in wavelength division multiplexing (WDM) optical networks, and propose a novel dynamic heuristic algorithm called differentiated reliable segment protection (DRSP). Differing from previous work, DRSP can effectively avoid the trap problem and is able to find a feasible solution for each connection request. Therefore, DRSP outperforms the previous work. Simulation results have shown to be promising.

Study and design of assembled CFDST column-beam connections considering column wall failure

Lei Guo,Jingfeng Wang,T.Y. Yang,Wanqian Wang,Binggen Zhan 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.39 No.2

Currently, there is a lack of research in the design approach to avoid column wall failure in the concrete filled double skin steel tubular (CFDST) column-beam connections. In this paper, a finite element model has been developed and verified by available experimental data to analyze the failure mechanism of CFDST column-beam connections. Various finite element models with different column hollow ratios () were established. The simulation result revealed that with increasing  the failure mode gradually changed from yielding of end plate, to local failure of the column wall. Detailed parametric analyses were performed to study the failure mechanism of column wall for the CFDST column-beam connection, in which the strength of sandwiched concrete and steel tube and thickness of steel tube were incorporated. An analytical model was proposed to predict the moment resistance of the assembled connection considering the failure of column wall. The simulation results indicate that the proposed analytical model can provided a conservative prediction of the moment resistance. Finally, an upper bound value of  was recommend to avoid column wall failure for CFDST column-beam connections.

Research on a new method to optimize the thermal characteristics of an engine nacelle cooling module

Lei Guo,Maojun Zhou,Jing Hu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.5

Heat reflow in the fan rotation center of a forced convection cooling system has a great influence on heat dissipation. In this research, a calculation model of the external flow field of an engine compartment’s cooling module was established. Computational fluid dynamics method was used to calculate and analyze the heat flow characteristics of the existing radiator. By comparing the calculations with the experimental results, the regions and the reasons for the heat reflow were found. The existing heat dissipation scheme was recalculated by using the secondary heat dissipation model, and an optimized and improved scheme was proposed to introduce a deflector cone structure to eliminate heat reflow. This structure was connected to the fan hood by four blades. The front end of the structure acted as a diversion for the conical structure, and the back end was a hollow cylinder structure, making it easier for the fluid to transition to the conical structure. Both ends and the distance between the vertebrae were set to range from 2-5 mm. The research results showed that the secondary heat dissipation model could more accurately describe the heat reflow problem of the engine compartment, the heat flow organization of the improved structure was more reasonable, and the temperature distribution was more uniform. Moreover, the theoretical heat dissipation effect of the improved structure was more than 10 % higher than that of the existing structure.

Response Surface Optimized Extraction of Flavonoids from Mimenghua and Its Antioxidant Activities In vitro

Lei Guo,Wen-Cheng Zhu,Ya-Ting Liu,Jiu-Yu Wu,An-Qi Zheng,Yan-Li Liu 한국식품과학회 2013 Food Science and Biotechnology Vol.22 No.5

The optimized extraction conditions of total flavonoids from mimenghua were determined by the Box-Behnken design and response surface methodology. The optimal conditions to achieve the maximum yield of flavonoids were determined as follows: ethanol concentration 68%(v/v), extraction temperature 72.4oC, liquid/material ratio 48:1mL/g, and extraction time 2 h. Under the optimized conditions, the extraction ratio of flavonoids was 15.44%. The crude extract was then purified by AB-8 macroporous adsorption resin, the flavonoids content in the purified extract increased to 90.43%. The antioxidant activities of the purified flavonoids were evaluated in vitro by scavenging capabilities of DPPH radical, hydroxyl radical and superoxide radical, reducing power and total antioxidant capacity. The results showed that the flavonoids have significant antioxidant activities, which can be used as a source of potential antioxidant.

Molecular characterization, activity analysis and transcriptional detection of chitinases encoded in the genome of Spodoptera exigua

Lei Hea,Huan Yu,Cun-Yi Xu,Ying Zhao,Fu-Xiang Yang,Ya-Dong Guo,Guo-Hua Huang 한국응용곤충학회 2019 Journal of Asia-Pacific Entomology Vol.22 No.2

Insect chitinases are necessary hydrolytic enzymes for chitin degradation, insect molting and metamorphosis. In this study, five chitinases encoded in the genome of Spodoptera exigua (SeCHIT7, SeCHIT11, SeCHIT12, SeCHIT13 and SeCHIT14) were identified by reverse transcription PCR. Phylogenetic analysis indicated that SeCHIT7 belonged to Group III, and SeCHIT11/12/13/14 belonged to Group VIII. Real-time quantitative PCR analyses showed that SeCHIT7 had an extensive transcription at the fourth- and fifth-instar larval and pupal stages, while SeCHIT11 had the highest transcription level at the egg stage, and the transcription of SeCHIT12 increased by over 1000 times from pre-pupal to pupal stage. Tissue-specific analyses showed that these three SeCHITs (SeCHIT7, SeCHIT11 and SeCHIT12) were mainly transcribed in the midgut and fat body. Chitinase activity assays suggested that the activity had a lower level at the egg stage and peaked at the pupal stage. The activities were increased by 9.4 times from egg to first-instar larval stage. Tissue specificity analysis showed that the highest activity was observed in the fat body, followed by hemolymph and cuticle of the pre-pupal stage. Overall, these results provided valid information for further research on the biological function and regulation of chitinases in S. exigua.

EQUIPMENT PERFORMANCE DEGRADATION ASSESSMENT BASED ON WAVELET SUPPORT VECTOR MACHINE

Lei Guo,Jin Chen 한국소음진동공학회 2008 한국소음진동공학회 국제학술대회논문집 Vol.2008 No.7

Improved Work Function of Preferentially Oriented Indium Oxide Films Induced by the Plasma Exposure Technique

Lei Yang,Shuai Guo,Qiuling Yang,Yuankun Zhu,Bing Dai,Hailing Yu,Pei Lei,Jiecai Han,Ying Hou,Jiaqi Zhu 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.6

The preferentially oriented In2O3 thin films were prepared on glass substrates by conventional magnetron sputtering with Ar+ plasma exposure at room temperature. Based on the x-ray diffraction, x-ray photoelectron spectroscopy, and UV photoelectron spectroscopy results, it was found that the Ar+ plasma exposure not only enhanced the low-temperature crystallization of In2O3 thin films, but also led to a dramatic improvement in the work function. Furthermore, it demonstrated that the shift mechanism of the work function in In2O3 thin films mainly combined with theelimination of oxygen defects and the change of the preferential orientation of In2O3 film surface.

Modelling and experiment of semi rigid joint between composite beam and square CFDST column

Lei Guo,Jingfeng Wang,Meng Zhang 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.34 No.6

Semi-rigid connections with blind bolts could solve the difficulty that traditional high strength bolts were unavailable to splice a steel/composite beam to a closed section column. However, insufficient investigations have focused on the performance of semi-rigid connection to square concrete filled double-skin steel tubular (CFDST) columns. In this paper, a component model was developed to evaluate the mechanical behavior of semi-rigid composite connections to CFDST columns considering the stiffness and strength of column face in compression and column web in shear which were determined by the load transfer mechanism and superstition method. Then, experimental investigations on blind bolted composite joints to square CFDST columns were conducted to validate the accuracy of the component model. Dominant failure modes of the connections were analyzed and this type of joint behaved semi-rigid manner. More importantly, strain responses of CFDST column web and tubes verified that stiffness and strength of column face in compression and column web in shear significantly affected the connection mechanical behavior owing to the hollow part of the cross-section for CFDST column. The experimental and analytical results showed that the CFDST column to steel-concrete composite beam semi-rigid joints could be employed for the assembled structures in high intensity seismic regions.