SummaryIn this study, a demand-based optimal design method is proposed for an oscillator (a single-degree-of-freedom system) with a parallel-layout viscous inerter damper (PVID). The proposed design method overcomes some deficiencies of the existing method, which is based on the fixed-point theory and is mainly suitable for tuned mass dampers. Moreover, for the fixed-point method, the inherent damping of the primary structure is neglected, and the global optimal solution cannot be obtained.The proposed method can obtain a more rational and practical design for the actual design by minimizing both the response and the cost. The design problem of a PVID-equipped oscillator is transformed into a multi-objective optimization problem that can be solved using the ε-constraint approach, which is consistent with the concept of demand-based design. The dynamic response of the oscillator and the force of the PVID (i.e., the cost factor) are evaluated according to theories of random vibration to reduce the number of calculations required. A computer program is developed to perform demand-based parametric design of a PVID-equipped oscillator. Several design cases were examined under different excitation conditions using the computer program, and dynamic time history analyses were then conducted to verify the designs obtained. The results show that the proposed optimal design method identifies satisfactory designs more effectively than the existing method by obtaining PVID design parameter values that better meet the performance demand and simultaneously minimize the cost. | INTRODUCTIONStructural vibrations induced by earthquake or wind loads can be attenuated by various means, including modifying the stiffness, masses, damping, or shape of the structure, and by providing passive or active counter forces.[1] Among numerous available methods, passive mitigation measures are the most widely used in building and bridge engineering. Passive vibration mitigation involves providing a structure with additional damping by installing dampers, and the effectiveness of damping has been confirmed by extensive scientific studies and practical applications. Many types of dampers are used in the passive vibration mitigation of building structures all over the world, such as metalyield dampers, friction dampers, viscoelastic dampers, viscous fluid dampers, tuned mass dampers, and tuned liquid dampers. The concept of tuned mass dampers dates back to the 1900s, when Frahm [2] introduced a tuned mass damper (TMD) to absorb the energy of vibrations, thereby reducing the amplitudes of motions. Den Hartog [3] modified the original TMD concept in the

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A target-based baseline correction algorithm that can directly assign acceleration/velocity/displacement values equal or close to preset target values is proposed in this study for correcting vibration acceleration signals with inconsistent initial velocities and displacements. Baseline shift or drift phenomena can arise for velocity and displacement values obtained by numerical integration of recorded acceleration signals using assumed initial values that are inconsistent with reality. Two indicators, the drift ratio and amplitude ratio, are also proposed to identify the degree of baseline drift and to evaluate the results of baseline correction. The traditional polynomial detrending algorithm has typically been used to remove unreasonable trends in time series, but insufficient attention has been paid to consistency between acceleration, velocity, and displacement, which is explicitly considered in the proposed algorithm. The target-based algorithm has two implementation schemes, that is, a precise scheme and a detrending scheme, which can be selected according to the degree of baseline drift. Three inconsistent vibration signals are considered to verify the validity of the proposed algorithm. The baseline shift or drift trends can be removed effectively using the proposed target-based algorithm with the drift ratio and amplitude ratio reduced to satisfactory ranges whereas the traditional method fails to correct these signals.

Topical Influential User Analysis (TIUA) is an important technique in Twitter. Existing techniques neglected relationship strength between users, which is a crucial aspect for TIUA. For modeling relationship strength, interaction frequency between users has not been considered in previous works. In this paper, we firstly introduce a poisson regression-based latent variable model to estimate relationship strength by utilizing interaction frequency. We then propose a novel TIUA framework which uses not only retweeting relationship but also relationship strength. Experimental results show that the proposed TIUA algorithm can greatly improve the precision and relevance on finding topical influential users in Twitter.