Gongcheng Kexue Yu Jishu/Advanced Engineering Science

The base isolation structure has a high requirement for integrity of the isolation layer, and the connection behavior of the isolation layer members affects the integrity and the seismic behavior of the isolation layer directly. In this paper, the welding connection mode between longitudinal reinforcements at the bottom of the beam was improved, the tensile tests were also carried out, and a new frame joint was proposed of the isolation layer for prefabricated concrete base isolation structure. Then, the finite element models of the new frame joint and traditional cast-in-place joint were established to simulate the seismic behavior and the structural integrity under the lateral repeated loads in ABAQUS. Finally, an improved connection mode for the new frame joint was proposed by comparing the difference of seismic behavior between the two kinds of joints. The results showed that the tensile strength of the specimen which connected by grooving and welding on the steel plate was close to that of the complete reinforcement, and could significantly reduce the bending deformation of the connecting steel plate. The bearing capacity, stiffness and energy dissipation capacity of the prefabricated frame joint were lower than that of the cast-in-place joint, but the deformation capacity was stronger. The bearing capacity, stiffness, and deformation capacity of the new frame joint on the prefabricated isolation layer increased when some anchored rebars were added to the ends of the prefabricated beam, the reinforcement ratio at the end of beams also increased, at the same time, the plastic development of the longitudinal reinforcement was delayed by the anchored rebars, so the energy dissipation capacity decreased. The load-bearing capacity, stiffness and deformation capacity of the improved prefabricated frame joint were all stronger than that of cast-in-place joint, so the improved new frame joint had an excellent structural integrity, and it could be used in practical engineering widely.

To meet the demand for green construction of power grids in the new era, it is urgent to develop and apply a new type of environment-friendly foundation for power grid projects. For this purpose, an improved thin-walled tapered-end grouted miniature steel pipe pile was proposed, and the uplift bearing characteristics of this pile were studied through field tests. With the project background of the 220 kV line Shuanglou-Jiaohe Dongguang north substation, 18 steel pipe piles with two pile diameters of 159 mm and 203 mm, two burial depths of 5 m and 8 m were designed under two conditions of grouting and no grouting. The effects of grouting on the load–displacement curves, uplift bearing capacities, and soil failure modes for different test piles were analyzed through on-site uplift bearing characteristic tests. Based on the failure mechanism of pile–soil interface obtained through the field tests, a finite element model incorporated the pile–soil interaction for the tests was established, and the uplift deformation and failure process of the steel pipe pile was numerically simulated and analyzed. The simulation results showed that the failure modes of the pile–soil interface were consistent with the field tests. By comparing the shear strength parameters and microstructure of the soil around the pile before and after grouting, the macroscopic and microscopic mechanism of the influence of grouting on the soil around the pile was analyzed. The test results are as follows: 1) The load–displacement curve of steel pipe pile changed from steep drop type to slow change type after grouting, and the grouting enhanced the ability of the pile foundation to resist plastic deformation. 2) The uplift capacity of steel pipe pile increased by 59%～148% after grouting, and the increase range was negatively related to the slenderness ratio of test pile. 3) There were few cracks in the surface soil at the failure state of uplift tests for the non-grouting steel pipe piles. The pile body was almost extracted, and the surface soil appeared radial and circumferential cracks at the failure state of the grouting steel pipe piles. 4) Many voids in soil were filled in the process of grouting, which improved the soil strength around the pile. Cement consolidation was formed around the steel pipe pile after grouting, and a shear surface was formed between the cement consolidation and soil. This conclusion was also supported by the numerical simulation results. The influence mechanism of grouting on the uplift bearing capacity of steel pipe pile was mainly reflected in the increase of shear area and side friction of soil around the pile. The engineering application showed that the proposed steel pipe pile had a short construction period, a high bearing capacity, and a low impact on the surrounding environment. These steel pipe piles have been well popularized and applied in the 220 kV line project Shuanglou-Jiaohe Dongguang north substation.

Generally, the noise transmitted in the optical path mainly includes the influence of optical power, external vibration interference, the intrinsic noise of the optical path, and the influence of thermal motion caused by environmental temperature changes. The optical fiber is extremely sensitive to environmental interference, and any environmental disturbance will bring corresponding phase errors. At the same time, if the signal is preprocessed and filtered, it is easy to cause some small information to be lost and increase reconstruction errors. Aiming at the problem of internal common mode noise affecting measurement accuracy and increasing reconstruction error in micron-level vibration measurement, a differential measurement system based on all-fiber Fabry–Perot (F–P) interference is established. Firstly, according to the phase equation of the F–P interference principle and the 2×2 single-mode fiber coupler during the transmission process, the through arm and the coupling arm have a phase difference of 90°. It is deduced that the signals received by the two output detectors are equal in amplitude and opposite in direct. Then the difference between the two signals can increase the overall signal amplitude, weaken the influence of common mode noise on the signal, and enhance the signal quality. Through the reconstruction displacement analysis of the interference signal, the experimental results show that the reconstruction error of the synthesized signal is reduced by 0.4% in the 2 μm sinusoidal vibration of the mirror. Under 1.4 μm vibration measurement on rough surface, the reconstruction error is reduced by 2.8%. The experimental results also show that the differential structure can reduce the vibration measurement reconstruction error, and the reconstructed waveform is smoother.

A hydrological simulation in the Huaihe River Basin (HRB) was investigated using two different models: a coupled land surface hydrological model (CLHMS), and a large-scale hydrological model (LSX-HMS). The NCEP-NCAR reanalysis dataset and observed precipitation data were used as meteorological inputs. The simulation results from both models were compared in terms of flood processes forecasting during high flow periods in the summers of 2003 and 2007, and partial high flow periods in 2000. The comparison results showed that the simulated streamflow by CLHMS model agreed well with the observations with Nash-Sutcliffe coefficients larger than 0.76, in both periods of 2000 at Lutaizi and Bengbu stations in the HRB, while the skill of the LSX-HMS model was relatively poor. The simulation results for the high flow periods in 2003 and 2007 suggested that the CLHMS model can simulate both the peak time and intensity of the hydrological processes, while the LSX-HMS model provides a delayed flood peak. These results demonstrated the importance of considering the coupling between the land surface and hydrological module in achieving better predictions for hydrological processes, and CLHMS was proven to be a promising model for future applications in flood simulation and forecasting

The main purpose of video background separation is to extract objects of interest from the video, but it is still one of the most challenging tasks in computer vision and other fields due to the influence of noise and lighting changes. The truncated nuclear norm (TNN) algorithm is a classic robust principal component analysis (RPCA) algorithm, which is widely used to separate the background and the front of the video. However, the truncated kernel norm in this algorithm does not have a high degree of approximation to the rank function in the traditional robust principal component analysis, resulting in poor stability and low accuracy in separating the front and background of the video in some complex scenes. To solve this problem, this paper proposes an improved truncated nuclear norm (improved truncated nuclear norm, ITNN) algorithm. The algorithm first replaces the kernel norm in the TNN model with a non-convex γ norm, and analyzes that the non-convex γ norm has a higher degree of approximation to the rank function than the kernel norm . Corresponding model; secondly, in order to solve the proposed model, this paper introduces the generalized alternating direction method of multipliers (GADMM) to solve the model; finally, the proposed ITNN algorithm is applied to multiple public videos In the previous background separation experiment, and by showing the foreground effects of different videos, the effectiveness of the ITNN algorithm was verified from a visual point of view. At the same time, the F-measure value of the video foreground extracted by the proposed algorithm and the comparison algorithm is calculated, which further verifies the effectiveness of the ITNN algorithm from the perspective of quantification. In addition, the experiment also recorded the running time of the video front and background separation of each algorithm, which verified the efficiency of the ITNN algorithm. In a word, this paper verifies the effectiveness and superiority of the proposed ITNN algorithm in the separation of video front and background through experiments.