In order to implement the test method to detect winding deformation excited by pseudorandom binary M-Sequences (The M-Sequence method), a detecting instrument for winding deformation synthetically based on the M-Sequence method and Frequency Response Analysis (FRA) is developed. Three kinds of the artificial failures aimed to simulate winding deformation were set in a pie-type winding. Comparative experiments between the M-Sequence method and FRA were carried out, and the results show that frequency response and statistical characteristics of the M-Sequence method are consistent with those of FRA in the common frequency band, which proves that the two methods have the same accuracy in terms of frequency response. Transfer function coefficients obtained by the M-Sequence method as well as changes in the map of the poles and/or zeros can also indicate winding deformation. The experiments confirm that the M-Sequence method is a feasible approach for identifying winding deformation. Moreover, the on-site experiment shows that frequency responses obtained through the two methods are coincident in the common frequency band, while differences exist between the poles/zeros obtained by transfer function and peaks/troughs in the frequency response curve obtained by FRA. The presented study of this new method demonstrates that it has some advantages over FRA and lays the foundation for further practical applications.
To monitor three-dimensional structural displacements in civil engineering, a stereovision displacement measurement method based on structure coordinate system is proposed in the present paper, and the absolute displacements of structure can be obtained through establishing the structure coordinate system and coordinate transformation. The center identification algorithm for circular target is studied to acquire the subpixel coordinates of center by combining Canny algorithm and Zernike algorithm. The epipolar constraint is introduced to conduct stereo matching of initial image pairs, and Kalman filtering and neighborhood searching algorithm are both employed to track circular targets on the left and right sequence images. To validate the effectiveness of the proposed method, a destructive test of concrete beams strengthened with ultraviolet-cured glass fiber reinforced polymer is performed in lab. Results show that the load–displacement curves obtained by the proposed stereovision method and linear variable differential transformer agree with each other; this verifies that the proposed stereovision method is feasible and effective for monitoring structural displacement in a destructive test.
[Abstract] In the past decades, Synthetic Aperture Radar (SAR) antennas have attracted much attention for its advantages over other optical based antennas in earth observation because of their all-weather and daylight independent capabilities. The large size membrane SAR antennas has the advantages of achieving large gain and good resolution with ultra light mass. In this paper, we have developed a foldable deployable structure to deploy a membrane antenna in two directions, longitudinal and lateral directions. The longitudinal deployment is driven by two symmetrically arranged deployable structures. Each of them has a six-bar linkage mechanism and two closed-cable-loops. Several motion controllable hinges fulfill the lateral deployment. The hinge is composed of a SMA actuator, tape springs and a motion control mechanism. In this paper, the six-bar linkage has been designed with an optimal method to meet the demand of simultaneous deployment of all frames and keeping in a common plane after they are fully deployed. To analyze the dynamic performance of the driving mechanism, the multibody dynamic analysis software ADAMS has been used. For large size antennas, the effect of the frame flexibility on the dynamic performance of the system cannot be ignored. Using ADAMS/Flex, we studied the effect of frame flexibility on the dynamic properties of the support structure. Also, the natural frequencies and mode shapes of the deployed structure have been analyzed using finite element method. In this paper, the structure of the motion controllable hinge is introduced and the relationship between the joint output torque with respect to its parameters is studied.
A test method to detect winding deformation by using pseudorandom binary M-Sequence excitation signals is proposed. This broadband excitation signal and the corresponding response from the winding are combined to obtain the analytic expression of the winding's transfer function by using a Recursive Least Square method. The coefficients, poles, and zeros of the transfer function can be used to describe the winding status, and any mechanical changes in the winding over time can be therefore detected. The steps and algorithms involved in using the M-Sequence method are presented, and a comparative simulation between the M-Sequence method and Frequency Response Analysis (FRA) is carried out using an equivalent circuit for the winding. Results of the simulation confirm that the response sensitivity of the M-Sequence method is as good as FRA in a common frequency band, and is actually more sensitive for slight winding deformations of series capacitance. The correlation factor of the transfer function coefficients, used as example, can also diagnose slight deformation. Additionally, significant differences exist in the map of the poles and/or zeros before and after deformation. The study confirms the feasibility of using the M-Sequence method for detection of winding deformation in transformers. Transfer function can have a wider application than frequency response curves, then analysis and judgment based on the transfer function may offer more analysis tools. The theory and simulation study of the new method provide supports for subsequent development of its corresponding detecting system as well as experimental research.
First-principles plane-wave pseudopotential calculations of the electron structure and energetics of the interfaces of clean and Ni-doped TiC/Fe are reported. We predicted the atomic structure, bonding, and the interface binding energy of TiC(100)/Fe(100) and TiC(100)/Fe(110). By comparing the interface bonding energy and the total charge density distribution, the interface have priority to combine in TiC(100)/Fe(100) and TiC(100)/Fe(110) ways, where the former’s interface binding energy is higher. So the structure of TiC(100)/Fe(100) is more stable. The doped Ni atoms have preferential access to Fe-based body and form FeNi alloy, and enhance the interface bonding energy, thus effectively reducing the system energy of TiC(100)/Fe(100) and TiC(100)/Fe(110) interfaces, increasing the bonding strength and stability of interfaces of the composite materials.
The paper presents a novel process for synthesis of ultrafine titanium carbide by reaction between TiOSO4 and Phenol-formaldehyde resins at different temperatures in the range of 1450°C–1500°C under argon cover for 1 hr. It was a new low-cost synthetic route for fabricating ultrafine TiC powders. The thermodynamic and reaction processes about phenolic resin’s cracking and reducing in the system of titanium oxide were studied. When the organic cracking reaction ended at 1000°C, amorphous carbon was provided by phenolic resin’s cracking. The grain size distribution of TiC synthesized from organic carbon was more narrower than that from inorganic carbon.
<p>To investigate the potential bearing uplift of long-span cable-stayed bridges, a 1/35 scaled double- tower bridge model was tested on four shake tables at Tongji University, China. A longitudinal floating system was first applied to the test model, <i>i.e., </i>the unlimited longitudinal but restrained transverse movements. Then, viscous fluid dampers (VFDs) were installed as the tower-deck connections to study their effects on alleviating the issue of bearing uplift at auxiliary piers. Test results showed that: (1) though ground motions were merely longitudinally input, there was a possibility of bearing uplift due to the longitudinal vibration of the towers combined with the vertical vibration of the deck; (2) the effectiveness of the VFDs on reducing the bearing force at the auxiliary pier was related to the characteristics of earthquakes; (3) compared with the deck longitudinal displacement, the effectiveness of VFDs on controlling its vertical displacement was insignificant.</p>
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)