Publications

Research on Midcourse Guidance Method of Large Elliptic Transfer Orbits Based on Velocity Gain Gudance

The Accurate Calculation of Fresnel Diffraction and Collins' Formula by Using the Fast Fourier Transform

In order to reduce the influence of the mixing and overlap of frequency spectrum on the calculated result in the calculation of the fast Fourier transform (FFT) of diffraction,the interval of sampling should be taken to be as small as possible.However,a many number of sampling leads to great difficult in general to FFT program with finite computer memory.In this paper,a error trace calculation methd is proposed based on the study of the mixing and overlap energy of frequency spectrum and the Fresnel diffraction integral.Using our method,the FFT program needs a little of computer memory to finish the calculation of Fresnel diffraction with the arbitrary interval of sampling and the demanded precision.This method can be extended conveniently to Collins formula.

RESEARCH ON PROPAGATION CHARACTERISTICS AND REINFORCEMENT METHOD OF PENETRATING CRACK AT RIB-TO-DIAPHRAGM WELDED JOINTS IN STEEL BRIDGE DECK

The rib-to-diaphragm welded joints in the deck of an orthotropic steel bridge is most prone to fatigue cracking. A FE model was established and fracture mechanics was used to study the reinforcement effect of angle steel reinforcement methods on the penetrating crack at fatigue vulnerable details. Based on the finite element model corresponding to a full-foot segment fatigue test model, a penetrating fatigue model was established for the cracks in rib-to-diaphragm welded joints, and the reinforcement effect was evaluated on two reinforcement techniques:bolted angle steel and the bolted steel plate beside a longitudinal rib. The results indicate that:the fatigue cracks at the welded joint in the rib-to-diaphragm of a steel bridge deck expand into a certain length and will develop into penetrating cracks, the deformation of the crack surface under stress conditions is complicated, the fatigue crack propagation characteristics of the inner and outer side of longitudinal ribs are not the same, and as the crack propagation progresses, the cracking mode of the crack tip will be dominated by composite cracking. The existing research results show that:the bolted angle steel reinforcement method can well inhibit the longitudinal rib and diaphragm connection details of the vulnerable part with the fatigue crack type I cracking. Therefore, the short crack propagation can be well suppressed. However, the reinforcement effect on penetrating fatigue cracks extended in a composite type in this detail is not as good as the short crack that have not penetrated the web; the reinforcement method of the half U rib steel plates bolted to the outside of longitudinal ribs can effectively reduce the equivalent stress intensity factor of penetrating fatigue cracks, and stay below the crack propagation threshold after reinforcement. It shows that the reinforcement method has a good reinforcement effect on penetrating fatigue cracks.

Automated identification and segmentation of urine spots based on deep-learning

Micturition serves an essential physiological function that allows the body to eliminate metabolic wastes and maintain water-electrolyte balance. The urine spot assay (VSA), as a simple and economical assay, has been widely used in the study of micturition behavior in rodents. However, the traditional VSA method relies on manual judgment, introduces subjective errors, faces difficulty in obtaining appearance time of each urine spot, and struggles with quantitative analysis of overlapping spots. To address these challenges, we developed a deep learning-based approach for the automatic identification and segmentation of urine spots. Our system employs a target detection network to efficiently detect each urine spot and utilizes an instance segmentation network to achieve precise segmentation of overlapping urine spots. Compared with the traditional VSA method, our system achieves automated detection of urine spot area of micturition in rodents, greatly reducing subjective errors. It accurately determines the urination time of each spot and effectively quantifies the overlapping spots. This study enables high-throughput and precise urine spot detection, providing important technical support for the analysis of urination behavior and the study of the neural mechanism underlying urination.

Object recognition with a wavelet‐transform‐based joint transform correlator

We built a new system for object recognition by combining the joint transform structure with the wavelet transform. The system can perform preprocessing and correlation in a single step. It has many good features including high antinoise capability and sharp correlation peaks without sidelobes. To test the effectiveness of this system, experimental results on a plane model are also given.

Experiment on Mechanical Behavior of Concrete Hollow-ribbed Floor with Different Box

Robustness Analysis on the Aerothermal Performance of Turbine Blade Squealer Tip

Abstract An improved efficient uncertainty quantification (UQ) analysis framework is proposed by the combination of sparse polynomial chaos expansion (PCE) and universal Kriging (UK) metamodel to obtain the surrogate model (UK-PCE). Moreover, a challenging analytical test function and an engineering test are considered to investigate the response performance of UK-PCE method. The results show that the UK-PCE method reduces the computational cost by more than 70% in comparison to the typical PCE method. Then this method was applied to the UQ of the aerodynamic and heat transfer performance of GE-E3 rotor blade squealer tip. Additionally, a series of uncertainty quantities visualization methods based on the data mining method, parallel computing method, and Delaunay triangulation method is proposed to reveal more enlightening uncertainty phenomena in the actual operation. The results of UQ show that under the influence of uncertain inputs, the leakage flow rate and downstream entropy increase will be significantly increased. The statistical average of tip heat flux has increased by 8.56% relative to the design value, and the probability of it deviating from the design value by 10% is as high as 43.27%. In addition, the three-dimensional tip heat flux deviation distributions calculated by the proposed uncertainty quantities visualization method reveal a coupling of the hot corrosion and thermal fatigue of the squealer tip. It is also indicated that under the influence of the uncertain inputs, there is a marked increase in blade tip flux, and the blade tip flux deviation has been maintained at a high value, about 13.0%. The results of sensitivity analysis show that the largest contributor to the uncertainty of the blade tip aerodynamic performance is the tip clearance deviation and its variance index to the uncertainty of leakage flow rate and downstream entropy increase is as high as 88.21% and 62.63%. Therefore, the geometric accuracy of the tip clearance should be strictly ensured in the turbine blade assembly and marching process. The influence of the inlet total temperature deviation on the uncertainty of the heat transfer performance of the squealer tip must also be taken into account. So a satisfactory control system should be designed in the actual operation of the gas turbine to make sure that the fluctuation of inlet total temperature can be attenuated rapidly.

Acoustic Performance Analysis of Impedance Compound Muffler with Aluminum Foam

The common reactive muffler has poor acoustic properties in high frequency, so aluminum foam is applied to the reactive muffler and the impendence compound muffler is designed. The acoustic performance of the muffler is analyzed; the interior sound field of the muffler is modeled and meshed in the ANSYS, then they are imported into SYSNOISE, and imposed reasonable boundary conditions to carry out the analysis of acoustic performance of the muffler. The results show that, compared to reactive muffler, the muffler with aluminum foam has a higher amount of noise reduction and a wider frequency band in middle and high frequency.

A Study on Turbine Unsteady Flow via PIV and Hotwire

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Jun Li, Ming Su; A Study on Turbine Unsteady Flow via PIV and Hotwire. AIP Conf. Proc. 5 June 2007; 914 (1): 580–586. https://doi.org/10.1063/1.2747484 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

Structural damage detection considering sensor performance degradation and measurement noise effect

Damage identification in underground tunnel structures with wavelet based residual force vector

Discrete pseudo-integrals

Adaptive CUSUM Chart for Real-Time Monitoring of Bivariate Event Data

Monitoring time-between-events (TBE) data, where the goal is to track the time between consecutive events, has important applications across various fields. Many existing schemes for monitoring multivariate TBE data suffer from inherent delays, as they require waiting until all components of the observation vector are available before making inferences about the process state. In practice, however, these components are rarely recorded simultaneously. To address this issue, Zwetsloot et al. proposed a Shewhart chart for bivariate TBE data that updates the process status as individual observations arrive. However, like most Shewhart-type charts, their method evaluates the process based solely on the most recent observation and does not incorporate historical information. As a result, it is ineffective in detecting small to moderate changes. To overcome this limitation, we develop an adaptive CUSUM chart that updates with each incoming observation while also accumulating information over time. Simulation studies and real-data applications demonstrate that our method substantially outperforms the Shewhart chart of Zwetsloot et al., offering a robust and effective tool for real-time monitoring of bivariate TBE data.

Bridge condition monitoring under moving loads using two sensor measurements

A novel damage detection approach using only two sensors to detect the damage in beam bridges subjected to a moving vehicle is proposed in this article. In this approach, a moving mass is considered representing a vehicle moving across the bridge, and structural vibration responses at two locations are measured from a pair of sensors. A moving window is defined with a certain length determined by the sampling frequency and the fundamental frequency of the measured responses. The windowed pair time series extracted from these two measured responses are used to calculate the cross-correlation, which is used to define the local damage index. A simply supported beam bridge subjected to a moving mass is simulated to demonstrate the effectiveness and accuracy of the proposed approach. Numerical results indicate that the proposed approach can accurately identify the single and multiple damages using both displacement and acceleration responses, even when the responses are smeared with a significant noise. This indicates a good robustness to the noise effect. Experimental verifications on a laboratory beam bridge model demonstrate that the proposed approach can successfully identify the damage location using different selections of sensor pairs. Both the numerical and experimental results demonstrate that the new damage index is a good candidate for structural damage detection with very limited measurement information.

Research on the influence of strike-slip fault slippage on production casing and control methods and engineering application during multistage fracturing in deep shale gas wells

Shear deformation often occurs during multistage fracturing of shale gas worldwide, increasing the operation cost of gas well completion and lowering the well's productivity; strike-slip fault slippage is thought to be a crucial underlying factor. This paper presents a detailed analysis of the influence of strike-slip fault slippage on casing inner diameter and establishes a technique for predicting casing inner diameter after fault slippage. Numerical simulation models were developed to simulate the process of fault slippage and calculate changes in the inner diameters of the casing, considering different engineering and geological conditions. The influential factors, including the fault strike angle, slip distance, radius-thickness ratio, and mechanical properties of the formation, were analyzed in engineering practice; the simulation results were shown to be consistent. Four methods, including adjusting the wellbore trajectory of shale gas horizontal wells, avoiding perforation at the formation interface, decreasing the fracturing parameters including the fracturing pressure, discharge capacity, volume of injecting fracturing fluid, and prediction of casing inner diameter after casing shear deformation, were proposed and verified through engineering application and theoretical calculation, respectively.

Temperature calibration of optical fiber attenuation differences induced measurement error of Raman distributed temperature sensor

The effect of optical fiber attenuation differences (AD) induced temperature error of Raman distributed temperature sensor (RDTS) is analyzed using the temperature demodulation algorithm. First of all, a novel method to address the effects caused by the AD between Stokes and anti-Stokes light is proposed. Furthermore, the temperature measurement error caused by additional AD of fiber temperature is also reduced by using a formula obtained by experimental data. The experimental results demonstrate that the RDTS system can measure different temperature zones more accurately.

Crack Causes of Manifold at a Sour Natural Gas Gathering Project

The cause and influence factors of crack of manifold were analyzed at a sour natural gas gathering project.Improper welding processes were the root causes.The failure characteristic of cracking was the typical delay cracking.

A dynamic visualization system for risk characterization and accident evolution of molten metal operation

The dynamic visualization system for risk characterization and accident evolution of molten metal operation takes steel smelting and electrolytic aluminum as scenes, taking the four typical accidents of explosion, spitting, tilting and leakage as the objects, 3Dmax+Substance Painter2 are used for modeling and mapping, and Unity3d+C# are used for development. The system consists of steel smelting and electrolytic aluminum subsystems, including the functional modules such as hazard & risk characterization, accident rehearsal, accident reconstruction, safety cognition, etc. It is expected to provide operators, managers and other relevant personnel with effective tools for accident evolution analysis, accident deduction analysis, and safety cognition, to reduce accidents.