Probabilistic Risk Assessment of RCC Dam Considering Grey-Stochastic-Fuzzy Uncertainty

Wenlong Chen,Xiaoling Wang,Minghui Liu,Yushan Zhu,Shaohui Deng 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.11

Greyness, randomness and fuzziness are three inseparable uncertainty factors influencing the safety of a roller compacted concrete dam (RCC dam), which can be regarded as a system reliability problem associated with multiple failure modes. Aiming at the current probabilistic risk analysis of RCC dams, most of the studies limited to single failure mode and single uncertainty. A probabilistic risk assessment method for dam under Grey-Stochastic-Fuzzy (GSF) uncertainty is proposed to consider the randomness and greyness of parameters and the fuzziness of the failure criteria. First, the fault tree model of an RCC dam is established based on Fault Tree Analysis (FTA). Then, bootstrap repeated sampling is embedded into grey system theory to quantify the grey properties of stochastic variables. The Latin Hypercube Sampling (LHS) function is improved to compensate for the inability of describing the fuzzy failure criteria. Finally, considering the correlated multiple failure modes, the proposed method is applied to analyze the parameter sensitivity and failure probability of the LDL dam in China. The results show that the proposed method is a high-efficiency, fastconvergence and more scientific method with reasonable outputs compared to common uncertainty probability analysis methods. The proposed method also provides an effective basis for the structural design and safety analysis of a concrete dam.

Effect of Nanoparticle Size on the Interface Bond Energy in KTa0.5Nb0.5O3 / Polyimide Composites

Chuntian Chen,Juan Wang,Wenlong Yang,Xiaokang Li,Jingyun Zhang 보안공학연구지원센터 2014 International Journal of Hybrid Information Techno Vol.7 No.6

The effects of particle size on the interface bond energy in KTa0.5Nb0.5O3/ polyimide composites were investigated using the molecular dynamics method. The composites of polyimide and the KTa0.5Nb0.5O3 nanoparticles with different size (0.4 nm, 0.5 nm, 0.6 nm, 0.8 nm, 1.2 nm, and 1.4 nm) have been established and simulated using the Forcite program package of Materials Studio software. The calculated results show that the interface bond energy is 38~150 Kcal/mol, which indicate the Van der Waals force exist between the nanoparticle and polyimide matrix. The interface bond energy of the smaller nanoparticle is greater than the lager nanaparticle due to the size effect. The introduction of the smaller nanoparticle could generate the stronger intermolecular bonding interaction between the nanoparticle and polyimide matrix.

An Improved Model Predictive Torque Control Strategy of a Shearer Semi-direct Permanent Magnet Synchronous Motor Based on Duty Cycle

Du Wenlong,Li Wei,Lu En,Sheng Lianchao,Chen Yuming,Jiang Song 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.5

In order to improve the stability of low-speed and high-torque permanent magnet synchronous motor control in the shearer semi-direct cutting system under large load fl uctuation and strong impact conditions, an improved model predictive torque control strategy based on duty cycle is proposed which can eff ectively reduce the fl ux and torque ripples and improve steadystate control performance. This method combines the separate process of the voltage vector selection and the duty cycle calculation through the predictive model combined with duty cycle. Then, the optimal voltage vector and its duration is selected simultaneously based on minimizing the cost function. In addition, in order to mitigates the computational burden of the proposed method, the voltage vectors in the fi nite control set is pre-selected using hysteresis comparator according to the motor operating status. Furthermore, the duty cycle pulse width modulation is introduced to obtain a fi xed switching frequency of the inverter. The results of simulation experiments confi rm that the proposed strategy can signifi cantly reduce the fl ux and torque ripples and improve the steady state performance while maintaining fast dynamic response.

Application of noise reduction and heat insulation based on controlled-size polystyrene hollow microspheres

Jiaxing Zhang,Wenlong Chen,Rui Zhai,Hui Chen,Zhihua Shan 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.115 No.-

Core/shell polymer microspheres containing carboxyl group were prepared by emulsion polymerization,and then the hollow polymer microspheres (PHMs) were formed by infiltration and swelling after alkalisolution post-treatment. Effects of emulsifier types and initial pH of alkali post-treatment on the particlesize distribution and morphology of PHMs emulsion were investigated. Foamed animal skin material(FAS) was obtained by cross-linking and curing the skin collagen materials with PHMs. The resultsshowed that the optimal initial pH was 9, and a stable PHMs emulsion with a maximum average particlesize of 888.5 nm was obtained. The average particle size order of the PHMs emulsions obtained with differentemulsifiers was: sodium stearate (1028.0 nm) > SDBS (823.6 nm) > cetyltrimethylammonium chloride(607.4 nm). The mechanical strength, porosity, and thermal stability of FAS were enhanced by PHMsdispersing and fixing, while its natural permeability and softness were retained. In addition, the whitenessand ultraviolet aging resistance of FAS were improved obviously. The thermal conductivity of FASwas reduced to 0.034 W/(Km), which was in line with the standard of polystyrene foam board for buildingmaterials. In the range of 2000 7000 Hz, the sound transmission loss of FAS reaches 25 40 dB.

Stabilization for a Class of Stochastic Nonlinear Systems with Arbitrary Switching via the Common Lyapunov Function Method

Jian Wu,Weisheng Chen,Jingli Du,Wenlong Ren 제어·로봇·시스템학회 2013 International Journal of Control, Automation, and Vol.11 No.5

This paper addresses the stabilization problem for a class of stochastic nonlinear systems with arbitrary switching. Based on the simultaneous domination approach, the common Lyapunov function method and the backstepping technique, a state feedback controller and an output feedback controller are designed, respectively. The closed-loop systems are proved to be globally asymptotically stable in probability. The main advantage of the proposed control schemes is that the controllers are independent of switching signal. Two simulation examples are given to illustrate the effectiveness of the proposed control strategies.

Effect of Bacterial Wilt on Fungal Community Composition in Rhizosphere Soil of Tobaccos in Tropical Yunnan

Yuanxian Zheng,Jiming Wang,Wenlong Zhao,Xianjie Cai,Yinlian Xu,Xiaolong Chen,Min Yang,Feiyan Huang,Lei Yu,Yuansheng He 한국식물병리학회 2022 Plant Pathology Journal Vol.38 No.3

Bacterial wilt, which is a major soil-borne disease with widespread occurrence, poses a severe danger in the field of tobacco production. However, there is very limited knowledge on bacterial wilt-induced microecological changes in the tobacco root system and on the interaction between Ralstonia solanacearum and fungal communities in the rhizosphere soil. Thus, in this study, changes in fungal communities in the rhizosphere soil of tobaccos with bacterial wilt were studied by 18S rRNA gene sequencing. The community composition of fungi in bacterial wilt-infected soil and healthy soil in two tobacco areas (Gengma and Boshang, Lincang City, Yunnan Province, China) was studied through the paired comparison method in July 2019. The results showed that there were significant differences in fungal community composition between the rhizosphere soil of diseased plants and healthy plants. The changes in the composition and diversity of fungal communities in the rhizosphere soil of tobaccos are vital characteristics of tobaccos with bacterial wilt, and the imbalance in the rhizosphere microecosystem of tobacco plants may further aggravate the disease.

The Influence of Composite Wave Field Fluctuation Parameters Matching to Permeability of Low Permeability Reservoirs

Zengli Xiao,Junbin Chen,Xiangqian Du,Wenlong Qin 보안공학연구지원센터 2016 International Journal of Smart Home Vol.10 No.7

There are essential differences in the influence rules of the binary composite wave generated by the combination of artificial resonance wave and hydraulic impulse wave to two-phase fluid flow of low permeability reservoirs porous media oil-water. When the fluctuation parameters of binary composite wave field reaching the optimal matching, the binary composite wave will have a good synergetic effect on two-phase fluid flow of oil-water, and the improvement effect on two-phase fluid flow of low permeability reservoirs oil-water will generate resonance effect which is far more effective than unary wave field. If the fluctuation parameters of binary composite wave field are not matched well, bad synergetic effect on two-phase fluid flow of oil-water will be generated ,not only it can’t raise the improvement effect on two-phase fluid flow of oil-water, but also it will make the improvement effect below unary wave field. Even there will be an inhibition effect on fluid flow of oil-water, which reduces the displacement efficiency and the availability of low permeability reservoirs water injection’s development. By using the indoor fluctuation oil recovery simulation experiment device, the influence rules of displacement vibration wave and hydraulic impulse binary composite wave field to low permeability reservoirs oil-water single phase and two-phase fluid flow feature were studied. The influence rules of amplitude, frequency, work cycle and the other important parameters of composite wave to the permeability of oil-water single phase was intensively studied. Finally the mechanism of the synergetic effect generated by composite wave to two-phase fluid flow of low permeability reservoirs was analyzed.

Non-probabilistic Integrated Reliability Analysis of Structures with Fuzzy Interval Uncertainties using the Adaptive GPR-RS Method

Minghui Liu,Xiaoling Wang,Xiaobin Zhu,Wenlong Chen,Xiao Li 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.9

Due to its weak dependence on the quantity of variable samples, the non-probabilistic reliability analysis method based on the convex set model is applicable to practical problems in structural engineering with inherent uncertainties. However, when dealing with the black-box limit-state function issues in practical complex structural engineering, the traditional quadratic polynomial response surface (QP-RS) method has the problem of insufficient precision in approximating a highly nonlinear function. Meanwhile, fixing the limits of interval variables is trickier in case of scant samples and meager statistical information. To remedy the above deficiencies, this paper introduces a reasonable integrated reliability analysis approach. First, an adaptive Gaussian process regression response surface (GPR-RS) method that dynamically improves the fitted accuracy near the design point of the black-box limit-state function is formulated. Furthermore, the integrated reliability index with consideration of fuzzy interval uncertainties is presented. Three validation and two application examples are employed, which have justified the approach as a more reasonable assessor of practical complex structural reliability with safer results.

Field Test on Uplift Bearing Capacity of Rock-Socketed Belled Piles

Qinke Wang,Jianlin Ma,Zili Xiao,Wenlong Chen,Yukun Ji 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.8

The thick sandstone with an upper layer of clay (2 m to 3 m) was identified at the transmission line projects in western China. Tower foundations are affected by extreme weather such as strong wind and snow all the year round, so the research of foundation uplift is very significant. Belled piles are widely used in the area due to its high uplift bearing capacity, however, further research studies regarding the uplift bearing capacity of the belled piles in this special scenario still need to be conducted. The uplift bearing characteristics of five rock-socketed belled piles were studied by field testing method. The load-displacement curves, fitting analysis of load-displacement curves, change rate of pullout stiffness, distribution of axial force alone the pile, and pile side friction were analyzed. Observation results show that the load-displacement curves of rock-socketed belled piles are steeply changed. Moreover, we find that the hyperbolic model can provide a good fitting result for load-displacement curves, and the ultimate uplift bearing capacity is suggested to be predicted by using a reduction parameter of 0.64 − 0.85. Both uplift bearing capacity coefficient Nu and utilization ratio of pile material ηincrease with the increase of L/d under a same diameter, while the growth rate decreases. In this paper, the significant size effect is observed with increasing of pile diameter. The change rate of pullout stiffness-displacement curves are consistent with the trend of the safety factor-displacement curves, and can be fitted by power function model. Additionally, the change rate of pullout stiffness at the limit state will decrease to around 154 in this study, which can be used as the instability threshold for the rock-socketed belled piles in a similar soil foundation.

EFFECTS OF WATER INJECTION ON COMBUSTION EMISSION AND KNOCK CHARACTERISTICS OF TURBOCHARGED DIRECT INJECTION GASOLINE ENGINE

Fuwu Yan,Junjun Wang,Dong Yan,Wenlong Zhang,Guoqing Zhang,Jizhou Zhang,Ziyi Chen,Yu Wang 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.4

This paper studied the effects of water injection on combustion, emissions and knock. The results showed that direct water injection (DWI) absorbed more heat than inlet port water injection (PWI), resulting in lower cylinder pressure, higher oxygen content and longer combustion duration. And the turbulence kinetic energy of DWI model was greater, resulting in lower soot and CO emissions of DWI. Furthermore, the cooling effect of exhaust port side WI was better than intake port side, which reduced NOX emission. Besides, the injection pressure of single injector WI was higher than double injector, which increased the combustion duration and reduced the cylinder pressure. The decrease of temperature under water dilution was the main reason for the reduction of NOX, while the increase of incomplete combustion increased the soot and CO emission. Finally, with the same amount of WI, the knock suppression effect of DWI models was better than PWI models. The knock intensity (KI) of all models decreased gradually with the increase of water, and DWI models decreased more rapidly. For PWI models, when the amount of water became smaller, the engine pressure fluctuation of certain areas in the cylinder increased slightly, weakening the influence of WI on engine knock.