268 research outputs found
Molecular mechanisms underlying the pathogenesis of nasal polyposis and its response to steroid treatment
Ph.DDOCTOR OF PHILOSOPH
FIELD LOADING-TEST BASED SHM SYSTEM SAFETY STANDARD DETERMINATION
Structural health monitoring (SHM) allows for real-time structural response monitoring and online data acquisition of bridge structures. This data reflects the operational and environmental conditions of the bridge, which is important in identification of possible anomalous changes. In order to effortlessly determine the safety condition of the bridge directly through the transferred data without data analysis, a five-level safety standard system will be established for real-time safety warning in this paper. The threshold of each safety levels will be determined through field loading tests results on an external prestressing rehabilitated continuous rigid frame bridge, of which permanent structural health monitoring system was instrumented. After overall evaluation, we come to the conclusion that the rehabilitation is successful and that the bridge is under safe operating condition. A novel, simplified safety standard thresholding technique is proposed based on static loading test results as well as ultimate limit state of the bridge. This technique is simple yet very practical in daily bridge monitoring
EVALUATION OF THE EFFECT OF EXTERNAL PRESTRESSED STEEL STRANDS ON CABLE-STAYED BRIDGES BASED ON FINITE ELEMENT ANALYSIS AND STATIC TEST
This article relies on the reinforcement project of the Mulinghe cable-stayed bridge to explore the changes in the mechanical properties of the reinforced concrete cable-stayed bridge before and after reinforcement. The bridge has large cable spacing, large internal force of a single cable, and the main beam is mainly Reinforced Concrete. Therefore, structural calculation, disease analysis, and damage state simulation are carried out. Afterwards, the bridge's commonly used reinforcement methods were compared, and suitable reinforcement schemes were selected. After the reinforcement, the field test was carried out on the cable-stayed bridge, the main beam deflection, the strain of the main beam and the main tower, and the increase in the cable force of the cable- stayed were analyzed. The results show that external prestressed reinforcement is the best way, which can significantly reduce the vertical displacement of the main beam and the horizontal displacement of the main tower, and also improve the stress on the upper and lower edges of the main beam. After the external prestressed reinforcement, the ratio of the observed value to the observed value in the filed load test of the cable-stayed bridge's decreased significantly. It is up to 31% increase in bending capacity of main beams and up to 24% increase in stiffness. This article is instructive for the reinforcement of the early-built sparse-cable reinforced concrete cable-stayed bridge, while also expanding the scope of implementation of external prestressed reinforcement technology
Experimental investigation on semi-active control of base isolation system using magnetorheological dampers for concrete frame structure
The traditional passive base isolation is the most widely used method in the engineering practice for structural control, however, it has the shortcoming that the optimal control frequency band is significantly limited and narrow. For the seismic isolation system designed specifically for large earthquakes, the structural acceleration response may be enlarged under small earthquakes. If the design requirements under small earthquakes are satisfied, the deformation in the isolation layer may become too large to be accepted. Occasionally, it may be destroyed under large earthquakes. In the isolation control system combined with rubber bearing and magnetorheological (MR) damper, the MR damper can provide instantaneous variable damping force to effectively control the structural response at different input magnitudes. In this paper, the control effect of semi-active control and quasi-passive control for the isolation control system is verified by the shaking table test. In regard to semi-active control, the linear quadratic regulator (LQR) classical linear optimal control algorithm by continuous control and switch control strategies are used to control the structural vibration response. Numerical simulation analysis and shaking table test results indicate that isolation control system can effectively overcome the shortcoming due to narrow optimum control band of the passive isolation system, and thus to provide optimal control for different seismic excitations in a wider frequency range. It shows that, even under super large earthquakes, the structure still exhibits the ability to maintain overall stability performance
When Source-Free Domain Adaptation Meets Label Propagation
Source-free domain adaptation, where only a pre-trained source model is used
to adapt to the target distribution, is a more general approach to achieving
domain adaptation. However, it can be challenging to capture the inherent
structure of the target features accurately due to the lack of supervised
information on the target domain. To tackle this problem, we propose a novel
approach called Adaptive Local Transfer (ALT) that tries to achieve efficient
feature clustering from the perspective of label propagation. ALT divides the
target data into inner and outlier samples based on the adaptive threshold of
the learning state, and applies a customized learning strategy to best fits the
data property. Specifically, inner samples are utilized for learning
intra-class structure thanks to their relatively well-clustered properties. The
low-density outlier samples are regularized by input consistency to achieve
high accuracy with respect to the ground truth labels. In this way, local
clustering can be prevented from forming spurious clusters while effectively
propagating label information among subpopulations. Empirical evidence
demonstrates that ALT outperforms the state of the arts on three public
benchmarks: Office-31, Office-Home, and VisDA
Study on Construction Resource Optimization and Uncertain Risk of Urban Sewage Pipe Network
With considering sewage pipe network upgrading projects in the “villages” in cities, the optimization of construction resources and the assessment of delay risks could be achieved. Based on the schedule-cost hypothetical theory, the mathematical model with constraint indicators was established to obtain the expression of optimal resource input, and conclude the method to analyze the schedule uncertainties. The analysis showed that cyclical footage of pipe could be regarded as a relatively fixed value, and the cost can be regarded as a function that depending on the number of working teams. The optimal number of teams and the optimal schedule occurred when the minimum total cost achieved. In the case of insufficient meteorological data, the Monte Carlo simulation method and uncertainty analysis method can be applied to assess the impact of rainfall on the total construction period, correspondingly the probability of such risk could be derived. The calculation showed that the risk of overdue completion varied significantly according to the construction starting time. It was necessary to take rainfall risk into consideration and make corresponding strategies and measures
Numerical Investigation of Turbulence Models for a Superlaminar Journal Bearing
With rotating machineries working at high speeds, oil flow in bearings becomes superlaminar. Under superlaminar conditions, flow exhibits between laminar and fully developed turbulence. In this study, superlaminar oil flow in an oil-lubricated tilting-pad journal bearing is analyzed through computational fluid dynamics (CFD). A three-dimensional bearing model is established. CFD results from the laminar model and 14 turbulence models are compared with experimental findings. The laminar simulation results of pad-side pressure are inconsistent with the experimental data. Thus, the turbulence effects on superlaminar flow should be considered. The simulated temperature and pressure distributions from the classical fully developed turbulence models cannot correctly fit the experimental data. As such, turbulence models should be corrected for superlaminar flow. However, several corrections, such as transition correction, are unsuitable. Among all the flow models, the SST model with low-Re correction exhibits the best pressure distribution and turbulence viscosity ratio. Velocity profile analysis confirms that a buffer layer plays an important role in the superlaminar boundary layer. Classical fully developed turbulence models cannot accurately predict the buffer layer, but this problem can be resolved by initiating an appropriate low-Re correction. Therefore, the SST model with low-Re correction yields suitable results for superlaminar flows in bearings
PARTNER: Level up the Polar Representation for LiDAR 3D Object Detection
Recently, polar-based representation has shown promising properties in
perceptual tasks. In addition to Cartesian-based approaches, which separate
point clouds unevenly, representing point clouds as polar grids has been
recognized as an alternative due to (1) its advantage in robust performance
under different resolutions and (2) its superiority in streaming-based
approaches. However, state-of-the-art polar-based detection methods inevitably
suffer from the feature distortion problem because of the non-uniform division
of polar representation, resulting in a non-negligible performance gap compared
to Cartesian-based approaches. To tackle this issue, we present PARTNER, a
novel 3D object detector in the polar coordinate. PARTNER alleviates the
dilemma of feature distortion with global representation re-alignment and
facilitates the regression by introducing instance-level geometric information
into the detection head. Extensive experiments show overwhelming advantages in
streaming-based detection and different resolutions. Furthermore, our method
outperforms the previous polar-based works with remarkable margins of 3.68% and
9.15% on Waymo and ONCE validation set, thus achieving competitive results over
the state-of-the-art methods.Comment: ICCV 202
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