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This study designed and manufactured a 1/5‐scale model of a three‐story steel frame structure. Various types of ground motions, including non‐long period (NLP) ground motions, near‐fault pulse type (NFPT) ground motions, and non‐pulse long‐period (NPLP) ground motions, were selected following the site conditions of the structure. The multiple unidirectional single‐particle damper (MUSPD) and its layout schemes were then designed. A series of shaking table tests for the three‐story steel frame with and without MUSPD were performed. Subsequently, a mechanical model of the multi‐degree‐of‐freedom structure with MUSPDs was established, and a corresponding numerical simulation method was proposed. The results revealed that MUSPDs achieved an average damping rate of 18.24% for peak and 27.41% for Root Mean Square (RMS). Notably, MUSPD exhibited a superior damping effect on the RMS of the structure compared to the peak. The distributing floor particle mass according to the first‐order mode of the structure resulted in excellent damping performance. Additionally, determining the particle movement distance for each floor involved calculating the optimal distance using a single‐degree‐of‐freedom structure. MUSPDs exhibited a better damping effect under NLP ground motions compared to NFPT and NPLP ground motions. The shaking table test results confirmed the rationality and feasibility of the proposed numerical simulation method, demonstrating a high level of accuracy. [ABSTRACT FROM AUTHOR]

The microstructure evolution of 022Cr25Ni7Mo4N duplex stainless steel after isothermal treatment for 2-20 h at 1100℃ was studied. The morphology evolution of austenite grain was observed and the grain size was quantitatively characterized. The change of element content in austenite and ferrite phase was measured. The effect of microstructure evolution on the anisotropy of volume fraction of ferrite phase and low temperature impact toughness of test steels was analysed subsequently. The results show that with the increase of holding time, there is obvious accumulation, growth and coarsening of austenite grain, accompanied by significant changes in grain morphology. The volume fraction of rod-like crystal grains with a/b value above 4.0 dropped from nearly 20% to below 5%, and that of equiaxed grains with a/b value between 1.0 and 1.9 increases significantly, while the number of grains with size above 20 μm increases rapidly. The prolongation of the holding time makes molybdenum and chromium elements diffuse and enrich to the ferrite phase further, which leads to the increase of pitting resistance equivalent number (PREN) value in ferrite phase. The significant decrease in the volume fraction of slender rod-like austenite crystallites is the primary reason for the improvement in anisotropy of austenite volume fraction and the increase of low temperature impact toughness of test steel.

Based on the net-worked radar observation model, we analyze the relationship between the ISAR images obtained simultaneously by different radars. We also propose a rotation velocity estimation algorithm based on image rotation and matching, and realize the target palstance estimation by one-dimensional search of rotation velocity. Simulation results show that the proposed algorithm can estimate the rotation velocity robustly based on the multi-radar images and the cross-range scaling can be achieved. The proposed algorithm can deal with the radar echoes for slowly moving targets and translation compensated targets, and fits for wide-band net worked radars of different center frequency and different bandwidth. [ABSTRACT FROM AUTHOR]