800 publications from this institution
The design parameters have been researched about the relative position that the scraper conveyor fixed into the loader,and the parameters are optimized.Through that,makes the scraper conveyor move to the most front of the loader to reduce the place that the loader couldn't load and raise the loading efficiency.
The bolster is one of the key components of a train. It is subjected to the complicated alternating load such as tensile, compression, torsion in various directions in practical application, and the fatigue crack initiation and propagation is the major failure mode of the bolster. In this paper, it is taken that the bolster of CRH2046 train after a period of service as the research object. Based on the fracture mechanics, the residual life prediction method of the bolster with the pre-existing cracks is researched. First, three-dimensional solid modeling and finite element strength analysis are carried out on the integral structure of the bolster with surrounding components to determine the stress distribution characteristics of the critical region of the bolster. Second, the sub-model technique is applied to establish the equivalent finite element model of the critical region. The function of stress intensity factor changing with crack morphology and relative crack depth is obtained. At last, the process of predicting the residual life the bolster under the two stage of the crack propagation is presented.
The pseudoliquid (PSL) armature with air spring is a novel railgun armature which has been fired successfully many times in a simple railgun by a united research group led by Beijing Institute of Special Electromechanical Technology (BISET), and the results of these experiments show that this armature can prevent transition in some conditions. Multiple turns in a railgun can significantly increase the inductance gradient of the launcher and decrease the needed current. Therefore, BISET initiated a program to launch projectiles with PSL armatures by a two-turn railgun. This paper presents an overview of this program, including the pulsed-power supply, a two-turn rail launcher, projectiles, and some experimental results. Further experimental studies are being continued.
This article proposes an improved multi-scale principal component analysis approach to recover the structural dynamic response in the time domain from data measured by performance-deteriorated sensors. The proposed approach builds on discrete wavelet transform, principal component analysis, and inverse discrete wavelet transform. The main approach is based on a cross-correlation calculation to better preserve the true structural vibration behavior as well as to recover the structural response from data measured by deteriorated sensors. Three sensor performance degradation models are considered in this study. Numerical studies are conducted first to demonstrate the effectiveness and accuracy of the proposed approach to recover the structural vibration response of an example spatial truss model considering sensor performance degradation under different loading scenarios. Experimental data on an in-field benchmark bridge are also analyzed to further validate and demonstrate the performance of the proposed approach.
ABSTRACT The problem of casing force and deformation during MPC (managed pressure cementing) injection pose great challenges to cementing in deep and ultra-deep Wells. According to the combination structure size of casing, the properties of multi-density and variable volume fluid in casing and annulus, the calculation method of multi-density fluid position change with injection time in cementing process is presented. Combined with causes of casing force during MPC injection stage, a temperature-pressure coupled mathematical model was established to calculate the temperature and pressure of casing caused by injection fluid flow in cementing. The calculation formula of U-tube effect was used to correct the parameters in the model. The energy conservation equation of casing and annulus is given, and wellbore pressure is obtain based on the theory of fluid mechanics. Taking a well A as an example, the model has been well used in pressure prediction and casing force analysis during MPC injection stage. The results show that the casing force is complicated during the injection process. The optimization of displacement can effectively alleviate casing deformation and make the bottom hole pressure in a safe state. The research results provide a theoretical basis for the optimization of construction parameters during MPC injection stage. INTRODUCTION The exploitation of ultra-deep oil and gas resources has promoted the continuous breakthrough of drilling technology. At present, there are more than 30 Wells in the world with a depth of over 9000m, which is of great significance for improving self-sufficiency in natural gas, increasing energy supply, optimizing and adjusting the energy structure, and improving people's livelihood. However, increasing well depth has brought great challenges to cementing. Many new problems have emerged (Rostami et al.; Thibodeaux et al., 2018), such as high cement slurry density, high circulating resistance, high liquid column pressure, high surface pump pressure for cementing, and high temperature and pressure formation. These problems have a serious impact on casing deformation during MPC injection stage.
The dynamic behavior of the cable-stayed bridge of Yibin Changjiang River Bridge at both construction and completion stages is calculated.The selected values of three-component coefficients of the main girder of the bridge are analyzed and the flutter and static stability thereof are checked through calculations.The results indicate that the wind-resistant stability of the bridge either in the state of the longest double cantilevers or single cantilever at construction stage or at completion stage is extremely safe and the divergent instability due to static torsion will not occur.Finally,proposals are made to add more damping measures to the stay cables,i.e.the magnetorheological fluid dampers could be added in addition to the internally-set rubber collar dampers.
As the typical series from of multi-terminal DC(MTDC) transmission technology , cascade multi-terminal UHVDC (CMT-UHVDC) power transmission technology has good prospects for development. Base on the typical connection mode and configuration consideration of CMT-UHVDC and according to the life cycle theory, the economic influence factors of CMT-UHVDC and Two-terminal UHVDC selection are quantitatively analyzed, providing reference for CMT-UHVDC selection.
With the build of Monitoring Center in our country, a great of signals are uploaded from many substations which are located on every corner. When an abnormal or a grid fault in Power System happens, lots of signals come out, then many operators on duty can’t often react quickly and judge the fault accurately.Recently，more and more scholars begin studying intelligent alarm processing system. In this paper, by analyzing signals characters and SCADA network of Monitoring Center, an intelligent processing frame to alarms in monitoring center is provided, the frame includes three layers named signals foundation treatment layer, signals connecting and sharing layer, signals intelligent diagnosis layer. Now the frame has been implemented successfully in Monitoring Center of our company. At the same time, based on an virtual signals software, lots of devices alarms and grid faults are simulated, this intelligent processing system, which are built on the frame, always show the alarm tip quickly. Facts prove it attributes to grid fault judge for operators of Monitoring Center.
Temperature drift, stress birefringence and low frequency vibration lead to the randomness and fluctuation of the output of optical voltage sensor(OVS). In order to solve the problem, this study adopts the lock-in amplifier technology with the aid of a high-speed rotating electrode to realize electric field modulation. This technology could shift the measured signal frequency band from near 50 Hz moved to several kilometer Hz, so as to make the output signal avoid the interference from low-frequency temperature drift, stress birefringence and vibration, leading to higher stability and reliability. The electro-optic coupling wave theory and static electric field finite element method are utilized to investigate the shape of modulation wave. The simulation results proves that lock-in technology is able to prevent the measured voltage signal from the large step signal interference and restore the perfect original signal. While the sample rate is decreased to the value of the modulation frequency.
In DFIG drivetrain, traditional two-level (2L) rotor-side converter (RSC) suffers from high thermal stress during its operation with high rotor current at low slip frequency. This paper presents the application of a three-level (3L) ANPC converter as the RSC in DFIG drivetrain. The thermal performance of the 3L-ANPC RSC is analyzed in details through numerical simulator approach for a wide operating range of DFIG RSC, and compared with the traditional 2L RSC employing continuous PWM and 60° DPWM modulation. The results show that 3L-ANPC RSC can effectively reduce device thermal stress across a wide operating range, especially at low slip frequency operation, of the RSC. This benefit enables improved reliability and lifetime of the RSC and DFIG wind drivetrain, and also indicates the capability to increase power rating and power density of the system.
Make a feasible schedule planning for software project, is the foundation to carry out an orderly software project activity, is the key to success of the project. To solve the difficulties of schedule planning, this article studies the science technology and methods, including four aspects: First, using network chart to show the dependencies between activities, including Precedence Diagram Method and Arrow Diagram Method; Second, Program Evaluation and Review Technique is used to evaluate the time of the project activity; Third, the critical path method of determining the project total duration, including deduce from calculation formula of active time and determine the critical path; Fourth, duration compression method based on progress compression factor method. According to the situation of many technologies and methods, studied the main factors considered by selecting techniques and methods. Results show that using scientific technology and method to make the schedule planning, will reduce the workload of planning, improve the accuracy of the plan and have high practical value.
Based on a sy stem of macro & m icro f racture appearance obser vation, energ y spect rum anal ysis, metallurgical st ructure inspection and the fr acture mechanism, the f racture cause o f the compres so r piston rod w as obtained. The results show ed that the piston rod w as over load fracture. Af ter the piston f ractur ed, driving for ce made the piston rod pr ess the cylinder components or the broken the piston, and led to the piston r od defo rmat ion and fracture.
A substructural damage identification approach based on structural response reconstruction in frequency domain is presented. The response reconstruction is based on transforming the measured responses into responses at other locations with the transmissibility matrix and then the relationship between two sets of response vectors is formulated. The damage identification is conducted by minimizing the difference between a measured response vector and the reconstructed response vector. Measured acceleration responses from the damaged substructure and the finite element model of the intact substructure only are required in the identification algorithm. A dynamic response sensitivity-based method with the adaptive Tikhonov regularization technique is adopted for the damage identification with improved results from noisy measurements. A seven-storey frame structure is taken as an example to illustrate the effectiveness and performance of the proposed approach.
