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Existing high dimensional two-sample tests usually assume that different elements of a high dimensional predictor are weakly dependent. Such a condition can be violated when data follow a low dimensional latent factor structure. As a result, the recently developed two-sample testing methods are not directly applicable. To fulfill such a theoretical gap, we propose here a Factor Adjusted two-Sample Testing (FAST) procedure to accommodate the low dimensional latent factor structure. Under the null hypothesis, together with fairly weak technical conditions, we show that the proposed test statistic is asymptotically distributed as a weighted chi-square distribution with a finite number of degrees of freedom. This leads to a totally different test statistic and inference procedure, as compared with those of Bai and Saranadasa (1996) and Chen and Qin (2010). Simulation studies are carried out to examine its finite sample performance. A real example on China stock market is analyzed for illustration purpose. [ABSTRACT FROM AUTHOR]

A new approach to identification of modal damping ratios from free vibration response of a linear structure with viscous damping is proposed in this paper. For a single degree of freedom (dof) system, the formulated relations among areas forming from time history of response are used to determine the damping ratio for the free decay vibration. Comparing with traditional logarithmic-decrement method, the approach in this paper has advantages such as stronger anti-noise ability, higher precision, better stability and convenience. For a multi-dof system, the free vibration response measured at one point on the structure is expressed in an analytical form at first, and then multiplied by e at . Giving the initial value, a can be obtained by Newton's dichotomy or golden section method while the product of the response and e at has equal vibration amplitudes after a period of time. Accordingly, the damping ratio for this mode can be determined. Repeating the above-mentioned process, all damping ratios for different modes can be obtained in the same way. Results of digital simulations and field tests for the Dongting Lake Cable-stayed Bridge in Yueyang show that the approach presented in this paper is effective and practical. [Copyright &y& Elsevier]