Reliability Analysis and Prediction on Tunnel Roof under Blasting Disturbance

Pengfei Wu,Tianjiao Yang,Weichao Jia 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.9

The parameters of underground structure have the characteristics of large spatial heterogeneity and strong uncertainty. Recently, people gradually begin to use the idea of probability to analyze the safety of underground structures. However, few articles analyze the dynamic response of structural reliability. In this paper, the reliability of tunnel roof under blasting disturbance is studied, and the influence of the number of disturbances and the distribution of random variables on the structural reliability is analyzed. The prediction model of structural reliability is proposed. The sensitivity of different parameters to the structural reliability is discussed. The results show that the traditional method of evaluating the structural safety status is more dependent on the design value of each parameter. However, the design value does not represent the true state of the structure in a completely accurate way, which will result in a certain deviation between the assessment of the structural safety state and the actual state. Single disturbance has a limited impact on the structural reliability, while repeated disturbances can still have a noticeable effect on the structural reliability. When the disturbance reaches a certain number of times, the reliability of the structure can drop sharply. This paper proposes the prediction function of structure reliability according to the decay of structure reliability after blasting disturbance. Only a small number of parameters are needed to predict the structure reliability at different times. The error between the forecast results and the actual results is about 1%. With the increase of the number of blasting disturbances, the sensitivity coefficient of the structural resistance factor gradually decreases, and the sensitivity coefficient of the loaded effect gradually increases. The control of the blasting strength should be gradually increased to ensure the structural safety. Even if the mean and mean square error of random variables are the same, different distribution forms will have a great impact on the calculation results.

Research on Calculation Method of Suspension Bridge Internal Force under Random Traffic Load

Pengfei Wu,Zhichun Fang,Xue Wang,Renyuan Wang,Qiang Xu 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.11

Suspension bridge is a flexible structure. The weight, location and number of traffic on the bridge will affect the geometric alignment of the bridge. Although the finite element software can analyze the geometric nonlinearity of the bridge, the calculation of random load combination in finite element software is huge. In this paper, based on the deformation coordination, static equilibrium and constitutive model of the bridge, the force expression considering the geometric nonlinearity of the bridge is derived. Finite element software is used to simulate the internal force of components of suspension bridge under train load and vehicle load. The accuracy is verified by comparing the finite element results. Considering the random number of traffics, the random location of traffics, and the random weight of traffics, this paper analyzes the stress state of bridge under the random process of train load and vehicle load respectively. The method in this paper can be well used to analyze the actual stress state of the bridge, and provide a theoretical basis for related calculations.

Reliability Evaluation and Prediction of Deep Buried Tunnel Based on Similarity Theory and Model Test

Pengfei Wu,Zhichun Fang,Xue Wang,Guangyi Zhu 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.6

Deep buried tunnel has a complex stress environment and large stress level. At present, it is difficult to dynamic monitoring for such tunnels. In order to make the safety evaluation and prediction of tunnel closer to the engineering practice, this paper deduces the tunnel reliability evaluation algorithm. The time-varying reliability of deep tunnel excavation process is analyzed and predicted. Based on the similarity theory, the actual deep tunnel excavation is simulated by indoor model test, the stress and deformation are monitored. The results show that after the tunnel excavation, the reliability of the structure does not decrease gradually, but increases slowly first and then decreases sharply. With the increase of the buried depth of the tunnel, the structural reliability decreases gradually. When the buried depth reaches a certain depth, the structural reliability will decrease rapidly. The influence of different parameters on the structural reliability has different sensitivity. The sensitivity of friction angle is the highest, and the sensitivity of gravity is the lowest. The sensitivity has little effect with the change of tunnel excavation time and tunnel buried depth. The accuracy of this method is verified by the comparative analysis of model box tests.

Feasibility of Free-Breathing, Non-ECG-Gated, Black-Blood Cine Magnetic Resonance Images With Multitasking in Measuring Left Ventricular Function Indices

Peng Pengfei,Yue Xun,Tang Lu,Wu Xi,Deng Qiao,Wu Tao,Cai Lei,Liu Qi,Xu Jian,Huang Xiaoqi,Chen Yucheng,Diao Kaiyue,Sun Jiayu 대한영상의학회 2023 Korean Journal of Radiology Vol.24 No.12

Objective: To clinically validate the feasibility and accuracy of cine images acquired through the multitasking method, with no electrocardiogram gating and free-breathing, in measuring left ventricular (LV) function indices by comparing them with those acquired through the balanced steady-state free precession (bSSFP) method, with multiple breath-holds and electrocardiogram gating. Materials and Methods: Forty-three healthy volunteers (female:male, 30:13; mean age, 23.1 ± 2.3 years) and 36 patients requiring an assessment of LV function for various clinical indications (female:male, 22:14; 57.8 ± 11.3 years) were enrolled in this prospective study. Each participant underwent cardiac magnetic resonance imaging (MRI) using the multiple breath-hold bSSFP method and free-breathing multitasking method. LV function parameters were measured for both MRI methods. Image quality was assessed through subjective image quality scores (1 to 5) and calculation of the contrast-to-noise ratio (CNR) between the myocardium and blood pool. Differences between the two MRI methods were analyzed using the Bland–Altman plot, paired t-test, or Wilcoxon signed-rank test, as appropriate. Results: LV ejection fraction (LVEF) was not significantly different between the two MRI methods (P = 0.222 in healthy volunteers and P = 0.343 in patients). LV end-diastolic mass was slightly overestimated with multitasking in both healthy volunteers (multitasking vs. bSSFP, 60.5 ± 10.7 g vs. 58.0 ± 10.4 g, respectively; P < 0.001) and patients (69.4 ± 18.1 g vs. 66.8 ± 18.0 g, respectively; P = 0.003). Acceptable and comparable image quality was achieved for both MRI methods (multitasking vs. bSSFP, 4.5 ± 0.7 vs. 4.6 ± 0.6, respectively; P = 0.203). The CNR between the myocardium and blood pool showed no significant differences between the two MRI methods (18.89 ± 6.65 vs. 18.19 ± 5.83, respectively; P = 0.480). Conclusion: Multitasking-derived cine images obtained without electrocardiogram gating and breath-holding achieved similar image quality and accurate quantification of LVEF in healthy volunteers and patients.

ESPO Based Course-tracking Control of Ships with Input Delay

Yanbin Wu,Pengfei Gao,Rui Wu,Jialu Du 제어·로봇·시스템학회 2023 International Journal of Control, Automation, and Vol.21 No.3

Consider the course-tracking control issue of ships with the dynamic parameter uncertainties, unknown time-varying ocean environment disturbance, and input delay. This paper creates a novel ship course-tracking control solution scheme under a uniformed framework such that the ship course tracks the desired course. Therein, an extended state predictor observer (ESPO) is constructed to estimate the course and the yaw rate of ships as well as the total disturbance caused by ship dynamic parameter uncertainties and unknown time-varying environment disturbance at the future instants, and whereby eventually contributes to compensating both the input delay and the total disturbance. Theoretical analyses indicate that our developed ship course-tracking control law with ESPO achieves the uniform stability of ship course-tracking closed-loop control system. Simulation results and simulation comparisons on a frigate demonstrate the effectiveness and superiority of our developed control law for ships with input delay.

Performance Analysis of Carbon Black/Carbon-Fiber Double-Layer Spacer Fabric/Epoxy Resin Composite Materials

Pengfei Zhang,Kaichang Kou,Zhifeng Deng,Guanglei Wu 한국섬유공학회 2019 Fibers and polymers Vol.20 No.4

In this paper, the carbon-fiber double-layer spacer fabric (CFDSF) was firstly introduced into epoxy resin (EP) forfabrication of CFDSF/EP composite materials. It is indicated that the introduction of CFDSF can significantly improve themechanical properties of EP. Meanwhile, the influence of the content of modified carbon black (CB) on the mechanical andelectrical properties of CB/CFDSF/EP composite materials was investigated. The results showed that the flexural strengthand impact strength of the CB/CFDSF/EP composite materials were improved as the modified CB content increased to 3 %. The bending and impact strengths were found to be 123.8 MPa and 15.88 kJ/m2, respectively, owing to a fracture mechanismtransition induced via the addition of modified CB. As the modified CB content increased from 6 % to 15 %, the bending andimpact strengths exhibited a decreasing trend and typical brittle features were evident in the composite. Further, the volumeresistance of the CB/CFDSF/EP composite materials also presented a decreasing trend.

A three-region movable-boundary helical coil once-through steam generator model for dynamic simulation and controller design

Wu Shifa,Li Zehua,Wang Pengfei,Su G.H.,Wan Jiashuang 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.2

A simple but accurate mathematical model is crucial for dynamic simulations and controller design of helical coil once-through steam generator (OTSG). This paper presents a three-region movable boundary dynamic model of the helical coil OTSG. Based on the secondary side fluid conditions, the OTSG is divided into subcooled region (two control volumes), two-phase region (two control volumes) and superheated region (three control volumes) with movable boiling boundaries between each region. The nonlinear dynamic model is derived based on mass, energy and momentum conservation equations. And the linear model is obtained by using the transfer function and state space transformation, which is a 37-order model of five input and three output. Validations are made under full-power steady-state condition and four transient conditions. Results show good agreements among the nonlinear model, linear model and the RELAP5 model, with acceptable errors. This model can be applied to dynamic simulations and controller design of helical coil OTSG with constant primary-side flow rate.

Chromogenic/Fluorogenic Ensemble Chemosensing Systems

Wu, Jiasheng,Kwon, Bomi,Liu, Weimin,Anslyn, Eric V.,Wang, Pengfei,Kim, Jong Seung American Chemical Society 2015 Chemical reviews Vol.115 No.15

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Hsa_circ_0003602 Contributes to the Progression of Colorectal Cancer by Mediating the miR-149-5p/SLC38A1 Axis

Wu Rong,Tang Shiyu,Wang Qiuxiao,Kong Pengfei,Liu Fang 거트앤리버 소화기연관학회협의회 2023 Gut and Liver Vol.17 No.2

Background/Aims: We aimed to investigate the role and working mechanism of Homo sapiens circular RNA_0003602 (hsa_circ_0003602) in colorectal cancer (CRC) development. Methods: The expression of circ_0003602, miR-149-5p, and solute carrier family 38 member 1 (SLC38A1) was detected by quantitative real-time polymerase chain reaction. RNase R assays were conducted to determine the characteristics of circ_0003602. CCK-8 assays, flow cytometry analysis, transwell invasion assays, wound healing assays and tube formation assays were employed to evaluate cell viability, apoptosis, invasion, migration, and angiogenesis. All protein levels were examined by Western blot or immunohistochemistry assay. The glutamine metabolism was monitored by corresponding glutamine, α-ketoglutarate and glutamate assay kits. Dualluciferase reporter assay was utilized to confirm the targeted combination between miR-149-5p and circ_0003602 or SLC38A1. A xenograft tumor model was established to analyze the role of circ_0003602 in CRC tumor growth in vivo. Results: Circ_0003602 was upregulated in CRC tissues and cell lines. Circ_0003602 silencing suppressed CRC cell viability, migration, invasion, angiogenesis, and glutaminolysis; induced cell apoptosis in vitro; and blocked tumor growth in vivo. Moreover, circ_0003602 directly interacted with miR-149-5p to negatively regulate its expression, and circ_0003602 knockdown suppressed the malignant behaviors of CRC cells largely by upregulating miR-149-5p. MiR-149-5p directly bound to the 3’ untranslated region of SLC38A1 to induce its degradation, and miR-149-5p overexpression reduced the malignant potential of CRC cells largely by downregulating SLC38A1. Circ_0003602 positively regulated SLC38A1 expression by sponging miR-149-5p in CRC cells. Conclusions: Circ_0003602 knockdown impedes CRC development by targeting the miR-149- 5p/SLC38A1 axis, which provides a novel theoretical basis and new insights for CRC treatment.

Thickness effect on the stability of unipolar resistance switching in tin ferrite thin films

Gong, Guodong,Wu, Changjin,Hu, Pengfei,Li, Ying,Kwon, Namic,Liu, Chunli Elsevier 2016 CURRENT APPLIED PHYSICS Vol.16 No.9

<P>We report the reproducible unipolar resistance switching behavior in Pt/SnFe2O4/Pt structures. The amorphous SnFe2O4 thin film was spin-coated on the Pt/TiO2/SiO2/Si substrate by a sol-gel method. The current-voltage characterization showed that as the spin coating cycles increased, the resistive switching (RS) characteristics became stable, and an excellent RS performance showing uniform set voltage distribution, stable resistance of both low resistance and high resistance states, and narrow reset current distribution can be obtained in SFO films with a thickness about 220 nm. Based on the conducting filament model, the variation of the RS behavior was ascribed to the increase of the electroforming voltage in the thicker films, which consequently induced more oxygen vacancies to participate in the RS process. Our results indicated that the electroforming voltage performs a significant role in the RS properties of the amorphous SnFe2O4 and the optimized RS behavior through the regulation of preparation process can be used for the resistance random access memory applications. (C) 2016 Elsevier B.V. All rights reserved.</P>