800 publications from this institution
There are many problems existing in basic accounting work of oil and gas field companies related to current account, heavy repair expenditure, materials, capital and accounting documents. The causes are investigated and observed so as to find out corresponding measures to improve quality of basic management work. Suggestions such as enhancing propaganda, ascertaining responsibilities, improving quality of financial personnel and strengthening check and audit are proposed.
Convolutional neural networks have been widely employed for structural health monitoring and damage identification. The convolutional neural network is currently considered as the state-of-the-art method for structural damage identification due to its capabilities of efficient and robust feature learning in a hierarchical manner. It is a tendency to develop a convolutional neural network with a deeper architecture to gain a better performance. However, when the depth of the network increases to a certain level, the performance will degrade due to the gradient vanishing issue. Residual neural networks can avoid the problem of vanishing gradients by utilizing skip connections, which allows the information flowing to the next layer through identity mappings. In this article, a deep residual network framework is proposed for structural health monitoring of civil engineering structures. This framework is composed of purely residual blocks which operate as feature extractors and a fully connected layer as a regressor. It learns the damage-related features from the vibration characteristics such as mode shapes and maps them into the damage index labels, for example, stiffness reductions of structures. To evaluate the efficacy and robustness of the proposed framework, an intensive evaluation is conducted with both numerical and experimental studies. The comparison between the proposed approach and the state-of-the-art models, including a sparse autoencoder neural network, a shallow convolutional neural network and a convolutional neural network with the same structure but without skip connections, is conducted. In the numerical studies, a 7-storey steel frame is investigated. Four scenarios with considering measurement noise and finite element modelling errors in the data sets are studied. The proposed framework consistently outperforms the state-of-the-art models in all the scenarios, especially for the most challenging scenario, which includes both measurement noise and uncertainties. Experimental studies on a prestressed concrete bridge in the laboratory are conducted. The proposed framework demonstrates consistent damage prediction results on this beam with the state-of-the-art models.
In order to improve the quality of massive online open courses (MOOCs), we proposed an evaluation method applying a triangular fuzzy analytical hierarchy process (FAHP)-based comprehensive evaluation model. In the model, FAHP was used to determine the weights of indexes at each level, which proved effective in avoiding the fuzziness of expert evaluations in index assignment. In addition, we also illustrated how to construct the evaluation model, taking maritime-related vocational education as an example. The research results showed that the proposed model is scientific and rational, and can be well-applied to the reality.
SVG can compensate reactive power deficiency, suppress harmonics, improve three-phase imbalance and power quality more flexibly. There are very few small volume SVG products available for low voltage distribution network in the past. The generic SVG products are very expansive, thus not suitable for low voltage distribution network. Therefore, it is an urgent task to design a new generation distribution network SVG product that offers good value for money. This paper studied a SVG digital controller based on TMS320F28335 DSP chip. The fast and powerful computing and parallel operation capability of TMS320F28335 can satisfy the real-time, multifunction and multiple objective coordination control of SVG. Applied the instantaneous reactive power theory and adopted current direct control mode, an enhanced filtering algorithm to filter instantaneous sampling value is proposed. Automatic bi-directional compensation control strategy effectively reduced voltage variation at the user side. Its effectiveness is verified by an engineering project.
This paper proposes a novel structural damage quantification approach using a sparse regularization based electromechanical impedance (EMI) technique. Minor structural damage in plate structures by using the measurement of only a single surface bonded lead zirconate titanate piezoelectric (PZT) transducer was quantified. To overcome the limitations of using model-based EMI based methods in damage detection of complex or relatively large-scale structures, a three-dimensional finite element model for simulating the PZT–structure interaction is developed and calibrated with experimental results. Based on the sensitivities of the resonance frequency shifts of the impedance responses with respect to the physical parameters of plate structures, sparse regularization was applied to conduct the undetermined inverse identification of structural damage. The difference between the measured and analytically obtained impedance responses was calculated and used for identification. In this study, only a limited number of the resonance frequency shifts were obtained from the selected frequency range for damage identification of plate structures with numerous elements. The results demonstrate a better performance than those from the conventional Tikhonov regularization based methods in conducting inverse identification for damage quantification. Experimental studies on an aluminum plate were conducted to investigate the effectiveness and accuracy of the proposed approach. To test the robustness of the proposed approach, the identification results of a plate structure under varying temperature conditions are also presented.
The accuracy of structural damage identification is affected by the uncertainties in the vibration measurements and the finite element modeling. This paper proposes a novel approach based on sparse deep belief network (DBN) for structural damage identification with uncertain and limited data. Vibration characteristics, that is, natural frequencies and mode shapes, are extracted as the input to the network, while the output are the damage locations and severities of the structure. DBN is chosen to train the generated data sets and identify structural damages. Restricted Boltzmann Machines (RBMs) are used as building blocks to composite a DBN. To further enhance the capacity of the RBMs, an arctan-based sparse constraint is utilized to enable the hidden units to become sparse. This is achieved by adding an arctan norm constraint on the whole of the hidden units' activation probabilities. Numerical and experimental studies are conducted to verify the accuracy and performance of the proposed method. Undetermined damage identification is conducted, in which the quantity of input modal data is less than that of the system parameters to be identified. The identification results show that the proposed sparse DBN based on arctan can identify the damage effectively, and its accuracy is better than those obtained by other methods, even when the modeling uncertainty and the measurement noise exist and only limited data is available.
This article introduces the research and development for the China Galileo Test Range (CGTR) system, which includes indoor test environment (ITE) based on the microwave anechoic chamber, outdoor test environment (OTE) based on the pseudolite network and multimedia demonstration and training facility (MDTF) with multimode GNSS software receiver, application simulating facility, and multimedia platform. This article presents the key technical topics of CGTR and the system status by now. The topics are valuable for GNSS receiver testing, in indoor and outdoor test environment designing, multimode GNSS software receiver designing and GNSS application simulations.
Abstract the entrance portal of No.8 tunnel of F3 bid section of E60 highway in Georgia is shallow buried and under unsymmetrical pressure, which leads to high risk and difficulty in tunnel construction. Tunnel 8 is designed based on ADECO-RS (analysis of controlled deformation in rock and soil). In order to understand the stability characteristics of tunnel portal in the whole section construction process and determine reasonable and feasible engineering countermeasures, the numerical simulation analysis of tunnel construction process is carried out. We not only studied the relationship between the stability of the slope at the entrance and the stability of the whole tunnel body under the actual stratum conditions, but also studied the mechanical and deformation characteristics of the surrounding rock and supporting structure of the tunnel.The numerical analysis results show that the stability characteristics of the portal slope directly affect the overall stability of the tunnel portal section; due to the disturbance of tunnel excavation, a large range of plastic zone appears at the interface of rock and soil at the portal section, resulting in large settlement deformation of vault. The collapse and deformation of the upper soil layer with poor engineering properties will cause excessive additional load on the supporting structure of the tunnel.Therefore, advance support measures should be taken to control the excessive deformation of vault. At the same time, due to the influence of asymmetric pressure, the supporting structure of the shallow buried side and the deep buried side of the tunnel appears obvious asymmetric pressure state. It is suggested to strengthen the stiffness of the shallow buried side support structure and adopt the asymmetric support structure to ensure the safety of the support structure.
Abstract A 6.9 magnitude earthquake hit Menyuan County, Haibei Prefecture, Qinghai Province, at 01:45 PM Beijing time on January 8, 2022 (17:45 PM GMT time on January 7, 2022). To explore the magnitude of the earthquake deformation and the affected area, this work combined optical remote sensing interpretation, interferometric synthetic aperture radar (InSAR) coseismic deformation extraction, and field surveys for research and analysis. Relying on the high-resolution Earth observation system of the Qinghai Remote Sensing Center for Natural Resources, high-resolution GF1D, GF2, and TRIPLESAT optical remote sensing images were acquired immediately after the earthquake. The airborne triangulation encryption method was used to carry out orthographic correction, fusion, and mosaic processing of digital orthophoto map (DOM) and digital surface model (DSM) images, and first-hand optical remote sensing images of the disaster areas were obtained. Based on differential InSAR (D-InSAR), small baseline subset InSAR (SBAS-InSAR) and lifting rail fusion methods, the coseismic deformation field and deformation rate of the lifting rail direction were obtained by using Sentinel-1A data processing before and after the earthquake. Combined with optical interpretation, InSAR deformation, and field investigation, the results show that the deformation trend of the line of sight (LOS) images to the north and south of the ascending and descending orbits show an obvious opposite trend. The surface shape variables are −50 to 45 cm and −65 to 72 cm, respectively, and the deformation rate before the earthquake reached 25 cm/year. The deformation field characteristics show that the earthquake was mainly due to thrust, and the coseismic deformation field fractured along the WNW‒ESE direction with a length of approximately 33 km. The areas affected by 10 mm, 20 cm, and 50 cm deformation magnitudes in the whole earthquake area were 975.14, 321.10, and 38.55 km 2 , respectively. Within 20 km, there were two main affected townships, namely, Sujitan Township and Huangcheng Mongolian Township. Within 50 km, there were four main affected towns and townships, namely, Sujitan Township, Mongolian Township of the Imperial city, Qingshizui town, and Haomen town.
Abstract Continuous rigid-frame bridge (CRFB) is widely constructed in western China with high seismicity areas. To investigate the seismic response characteristics and whiplash effect mechanism of CRFBs under near-fault ground motions, this study selects a long-span CRFB with high piers as the prototype bridge and develops the nonlinear finite element model based on OpenSees. In this work, three groups of near-fault ground motions having forward directivity pulse, fling-step pulse and non-pulse are selected as seismic inputs. These records are intercepted using significant duration index and scaled to 0.2 g, 0.4 g, and 0.64 g, representing basic ground motions, frequent ground motions and rare ground motions, respectively. The study analyzes the seismic response characteristics of CRFBs and discusses the effects of bearing constraints, ground motion components and vertical excitations on the seismic responses. The numerical results show that the longitudinal vibration, transverse whiplash effect and vertical uplift behavior of main girder are main deformation characteristics of CRFBs. Compared with non-pulse earthquakes, the structural displacements, lateral drift angles, bearing deformations, internal forces and pounding effects all significantly increase under pulse-like earthquakes. There are spatial torsional effects in mid-span girder and main piers and pounding effects between girder ends and transition pier top. The perfectly-free and fixed bearings in transverse direction are not recommended for the seismic design of CRFBs. An optimal stiffness ratio in friction pendulum systems may exist that can minimize bending degree of the main girder. Furthermore, the side-span girder under pure longitudinal excitations can uplift that is closely related to the pier-girder consolidation form and rotation of the main piers. The main piers may be tensioned under strong vertical excitations, which is an uncommon problem worthy of attentions.
Tonopah Test Range (TTR) in Nevada and Kauai Test Facility (KTF) in Hawaii are government-owned, contractor-operated facilities managed and operated by Sandia Corporation (Sandia), a wholly owned subsidiary of Lockheed Martin Corporation. The U.S. Department of Energy (DOE), National Nuclear Security Administration (NNSA), through the Sandia Field Office (SFO), in Albuquerque, New Mexico, administers the contract and oversees contractor operations at TTR and KTF. Sandia manages and conducts operations at TTR in support of the DOE/NNSA’s Weapons Ordnance Program and has operated the site since 1957. Navarro Research and Engineering subcontracts to Sandia in administering most of the environmental programs at TTR. Sandia operates KTF as a rocket preparation launching and tracking facility. This Annual Site Environmental Report summarizes data and the compliance status of the sustainability, environmental protection, and monitoring program at TTR and KTF through Calendar Year 2013. The compliance status of environmental regulations applicable at these sites include state and federal regulations governing air emissions, wastewater effluent, waste management, terrestrial surveillance, Environmental Restoration (ER) cleanup activities, and the National Environmental Policy Act. Sandia is responsible only for those environmental program activities related to its operations. The DOE/NNSA/Nevada Field Office retains responsibility for the cleanup and management of TTR ER sites. Environmental monitoring and surveillance programs are required by DOE Order 231.1B, Environment, Safety, and Health Reporting (DOE 2012).
Abstract A large number of pressure vessels and pipelines in China’s refining and chemical industry will soon enter the extended service period (more than 20 years). It is estimated that by 2025, the growth rate of pressure vessels in extended service will increase from the current 10 thousand units/year to 100 thousand units/year, thus the safety of these aging equipment is the focus of current attention. It is necessary to accurately evaluate and early warn the failure risk of these equipment, especially considering the complex influences, high uncertainty and suddenness of the failure in long-term service. On the other hand, the risk management methods of pressure vessels and pipelines are well-established based on API 571, API 581 and API 584. The commercial software is also developed for risk assessment and integrity management by some institutions and companies. However, at present, the risk assessment and control of equipment in refining and chemical industry are mainly based on the static data and static assessment methods, which have little correlations with the dynamic data from equipment operation and corrosion inspection. Based on the above requirements of corrosion management and risk control for the equipment in extended service, this study developed a dynamic risk management method and system, included the dynamic data interaction with Laboratory Information Management System (LIMS), Distributed Control System (DCS) and corrosion inspection systems, the damage identification diagnosis, the dynamic risk and residual life assessment, and the application of Integrity Operating Windows (IOWs). This paper also introduces the application of the system in crude distillation units as an example to explain the method in detail. The results show that the dynamic risk management system can effectively identify the real-time risks of aging equipment and give early warning to state parameters, which is important to avoid the failure of aging equipment.
In this note, we discuss when the concave integral coincides with the pan- integral with respect to the standard arithmetic operations + and ·. The subadditivity of the underlying monotone measure is one sufficient condition for this equality. We show also another sufficient condition, which, in the case of finite spaces, is necessary, too.
