Experimental and numerical investigations of hot-rolled austenitic stainless steel equal-leg angle sections

The present paper reports a thorough experimental and numerical study on the cross-section behaviour and resistances of hot-rolled austenitic stainless steel equal-leg angle section structural members. The experimental programme was performed on a total of five different angle sections, and involved ten stub column tests and ten laterally restrained 4-point bending tests about the cross-section geometric axes (parallel to the angle legs), together with measurements on material properties and initial local geometric imperfections. The testing programme was followed by a systematic finite element simulation programme, where the developed numerical models were firstly validated against the experimentally derived results and then employed to carry out parametric studies for the purpose of generating further structural performance data over a broader range of cross-section dimensions. The numerically derived results were then employed together with the test data to assess the accuracy of the established design rules for hot-rolled austenitic stainless steel equal-leg angle section stub columns and beams given in the European code. The results of the assessment revealed an overly high level of conservatism and scatter of the European code in predicting cross-section capacities of hot-rolled austenitic stainless steel equal-leg angle section stub columns and beams, which can be mainly attributed to the neglect of the beneficial material strain hardening. The continuous strength method (CSM) is a well-established design approach, taking due account of material strain hardening in the determination of cross-section resistances, and has been recently extended to cover the design of mono-symmetric and asymmetric stainless steel open sections in compression and bending about an axis that is not one of symmetry. The CSM was assessed against the experimental and numerical results on hot-rolled austenitic stainless steel equal-leg angle section stub columns and laterally restrained beams, and shown to result in substantially more precise and consistent cross-section capacity predictions than the European code

Combating Bilateral Edge Noise for Robust Link Prediction

Although link prediction on graphs has achieved great success with the development of graph neural networks (GNNs), the potential robustness under the edge noise is still less investigated. To close this gap, we first conduct an empirical study to disclose that the edge noise bilaterally perturbs both input topology and target label, yielding severe performance degradation and representation collapse. To address this dilemma, we propose an information-theory-guided principle, Robust Graph Information Bottleneck (RGIB), to extract reliable supervision signals and avoid representation collapse. Different from the basic information bottleneck, RGIB further decouples and balances the mutual dependence among graph topology, target labels, and representation, building new learning objectives for robust representation against the bilateral noise. Two instantiations, RGIB-SSL and RGIB-REP, are explored to leverage the merits of different methodologies, i.e., self-supervised learning and data reparameterization, for implicit and explicit data denoising, respectively. Extensive experiments on six datasets and three GNNs with diverse noisy scenarios verify the effectiveness of our RGIB instantiations. The code is publicly available at: https://github.com/tmlr-group/RGIB.Comment: Accepted by NeurIPS 202

Method of Multi-dimensional Gross Errors Snooping of GPS Velocity Estimation in Airborne Gravimetry

Precision velocity plays an important role in airborne gravimetry. Since the aircraft in a state of stable flight, we could establish a strict state equation with constant acceleration model for it, then obtained predicted velocity which was used for constructing a priori residual Q to detect the gross errors. Theoretical research showed that Q was influenced by the accuracy of predicted velocity and the measurement errors. According to the statistical features of Q combined with IGG Ⅲ principle, we could lower the contribution of the observation that contained the gross errors. Static testing was used for analyzing the characteristic of measurement errors as well as the accuracy of predicted velocity under the simulated ideal flight environment where the acceleration was approximate to a constant, the results also showed the relationship between the sampling rate and the ability of detecting gross errors. Both the static and kinematic tests demonstrate that new method can well detect the gross error smaller than 1 cycle

Pre- and Postcollapse Ground Deformation Revealed by SAR Interferometry: A Case Study of Foshan (China) Ground Collapse

On the evening of 7 February 2018, a deadly collapse of a metro tunnel under construction in the Southern China city of Foshan caused 11 deaths, 8 injuries, and 1 missing person. For disaster prevention and mitigation, the spatiotemporal ground deformations before and after the collapse event were derived from 55 Sentinel-1A synthetic aperture radar (SAR) images spanning from March 2017 to January 2019. The results showed that prominent ground subsidence in the shape of a funnel with a maximum rate of 42 mm/year was observed in the vicinity of the collapse area before the accident. After the accident, the area and magnitude of subsidence decreased compared with precollapse subsidence. This decrease is related to the progress of tunnel excavation and groundwater changes. In the temporal domain, continuous subsidence was observed over a year before and after the accident, and accelerated subsidence appeared one month before the collapse accident. Soft soil consolidation and tunnel-induced soil losses were the main reasons for the subsidence over the study area. The leakage of groundwater accounted for the collapse event. The leaked groundwater eroded the soil, resulting in the formation of an arched hole. The connection between the arched hole and the tunnel reduced the bearing capacity of the soil layer above the arched hole, triggering the collapse event. The findings provide scientific evidence for future collapse monitoring and early warning due to tunnel excavation

A Kind of Single-frequency Precise Point Positioning Algorithm Based on the Raw Observations

A kind of single-frequency precise point positioning (PPP) algorithm based on the raw observations is presented in this paper. By this algorithm, the ionospheric delays were corrected efficiently by means of adding the ionospheric delay prior information and the virtual observation equations with the spatial and temporal constraints, and they were estimated as the unknown parameters simultaneously with other positioning parameters. Then, a dataset of 178 International GNSS Service (IGS) stations at day 72 in 2012 was used to evaluate the convergence speed, the positioning accuracy and the accuracy of the retrieved ionospheric VTEC. The series of results have shown that the convergence speed and stability of the new algorithm are much better than the traditional PPP algorithm, and the positioning accuracy of about 2-3 cm and 2-3 dm can be achieved respectively for static and kinematic positioning with the single-frequency observations' daily solution. The average bias of ionospheric total electron content retrieved by the single-frequency PPP and dual-frequency PPP is less than 5 TECU. So the ionospheric total electron content can be used as a kind of auxiliary products in GPS positioning

An Efficient Approximate Algorithm for Disjoint QoS Routing

Disjoint routing is used to find the disjoint paths between a source and a destination subject to QoS requirements. Disjoint QoS routing is an effective strategy to achieve robustness, load balancing, congestion reduction, and an increased throughput in computer networks. For multiple additive constraints, disjoint QoS routing is an NP-complete class that cannot be exactly solved in polynomial time. In the paper, the disjoint QoS routing problem was formulated as a 0-1 integer linear programming. The complicating constraints were included in the objective function using an adaptive penalty function. The special model with a totally unimodular constraint coefficient matrix was constructed and could be solved rapidly as a linear programming. An efficient algorithm using an adaptive penalty function and 0-1 integer linear programming for the disjoint QoS routing problems was designed. The proposed algorithm could obtain the optimal solution, considerably reducing the computational time consumption and improving the computational efficiency. Theoretical analysis and simulation experiments were performed to evaluate the proposed algorithm performance. Through the establishment of random network topologies using Matlab, the average running time, the optimal objective value, and the success rate were evaluated based on the optimal values obtained in Cplex. The simulation experiments validated the effectiveness of the proposed heuristic algorithm

Evaluation of the External Accord Accuracy of Airborne Gravity Data with Upward Continuation

Three methods for evaluating the external accord accuracy of airborne gravity survey line data, namely the gradient based, the Poisson integral based and the fast Fourier transform (FFT) based upward continuation (UPC) of terrestrial gravity, are introduced. A cross validation method is proposed for the estimation of terrestrial gravity errors and their propagation at flight altitude. The external accord accuracy of airborne gravity survey line data over Mu Us in Inner Mongolia is evaluated based on the three UPC methods and the proposed cross validation method. Numerical results show that the gridding interpolation error and representative error of terrestrial gravity range from 0.66 to 0.92 mGal, which demonstrates the necessity of removing these errors for error estimation of airborne gravity data. The Poisson integral and the FFT based UPC method are capable of evaluating the external accord accuracy of airborne gravity data, both have comparative performance. Applying the methods for the data acquired by GT-2A airborne gravimetry system over Mu Us in Inner Mongolia, it turns out the external accord accuracy of the airborne gravity disturbances is better than 1.42 mGal(1 Gal=1×10-2 m/s2) after the removal of terrestrial gravity error contribution,while some remaining integral edge effects still exist

Use of NTRIP for Optimizing the Decoding Algorithm for Real-Time Data Streams

As a network transmission protocol, Networked Transport of RTCM via Internet Protocol (NTRIP) is widely used in GPS and Global Orbiting Navigational Satellite System (GLONASS) Augmentation systems, such as Continuous Operational Reference System (CORS), Wide Area Augmentation System (WAAS) and Satellite Based Augmentation Systems (SBAS). With the deployment of BeiDou Navigation Satellite system(BDS) to serve the Asia-Pacific region, there are increasing needs for ground monitoring of the BeiDou Navigation Satellite system and the development of the high-precision real-time BeiDou products. This paper aims to optimize the decoding algorithm of NTRIP Client data streams and the user authentication strategies of the NTRIP Caster based on NTRIP. The proposed method greatly enhances the handling efficiency and significantly reduces the data transmission delay compared with the Federal Agency for Cartography and Geodesy (BKG) NTRIP. Meanwhile, a transcoding method is proposed to facilitate the data transformation from the BINary EXchange (BINEX) format to the RTCM format. The transformation scheme thus solves the problem of handing real-time data streams from Trimble receivers in the BeiDou Navigation Satellite System indigenously developed by China