Qiusheng Li

Bio: Qiusheng Li is an academic researcher from City University of Hong Kong. The author has contributed to research in topics: Wind speed & Wind tunnel. The author has an hindex of 47, co-authored 429 publications receiving 8830 citations. Previous affiliations of Qiusheng Li include Chinese Ministry of Education & Guangzhou University.

Integrated wind‐induced response analysis and design optimization of tall steel buildings using Micro‐GA

Abstract: SUMMARY This paper presents an integrated procedure for wind-induced response analysis and design optimization for rectangular steel tall buildings based on the random vibration theory and automatic least cost design optimization technique using Micro-Genetic Algorithm (GA). The developed approach can predict wind-induced drift and acceleration responses for serviceability design of a tall building; the technique can also provide an optimal resizing design of the building under wind loads to achieve cost-efficient design. The empirical formulas of wind force spectra obtained from simultaneous measurements of surface pressures on various rectangular tall building models in wind tunnel tests are verified testified using a published example. Upon the known wind force spectra, the equivalent static wind loads for every storey, such as along-wind, across-wind and torsional loads, are then determined and applied for structural analysis including estimation of wind-induced responses. An improved form of GAs, a Micro-GA, is adopted to minimize the structural cost/weight of steel buildings subject to top acceleration and lateral drifts constraints with respect to the discrete design variables of steel section sizes. The application and effectiveness of the developed integrated wind-induced response analysis and design optimization procedure is illustrated through a 30-storey rectangular steel building example. Copyright © 2009 John Wiley & Sons, Ltd.

The jump phenomenon effect on the sound absorption of a nonlinear panel absorber and sound transmission loss of a nonlinear panel backed by a cavity

Abstract: Theoretical analysis of the nonlinear vibration effects on the sound absorption of a panel absorber and sound transmission loss of a panel backed by a rectangular cavity is herein presented. The harmonic balance method is employed to derive a structural acoustic formulation from two-coupled partial differential equations representing the nonlinear structural forced vibration and induced acoustic pressure; one is the well-known von Karman’s plate equation and the other is the homogeneous wave equation. This method has been used in a previous study of nonlinear structural vibration, in which its results agreed well with the elliptic solution. To date, very few classical solutions for this nonlinear structural-acoustic problem have been developed, although there are many for nonlinear plate or linear structural-acoustic problems. Thus, for verification purposes, an approach based on the numerical integration method is also developed to solve the nonlinear structural-acoustic problem. The solutions obtained with the two methods agree well with each other. In the parametric study, the panel displacement amplitude converges with increases in the number of harmonic terms and acoustic and structural modes. The effects of excitation level, cavity depth, boundary condition, and damping factor are also examined. The main findings include the following: (1) the well-known “jump phenomenon” in nonlinear vibration is seen in the sound absorption and transmission loss curves; (2) the absorption peak and transmission loss dip due to the nonlinear resonance are significantly wider than those in the linear case because of the wider resonant bandwidth; and (3) nonlinear vibration has the positive effect of widening the absorption bandwidth, but it also degrades the transmission loss at the resonant frequency.

Moho-mapping in the Dabie ultrahigh-pressure collisional orogen, central China

Abstract: Eight wide angle reflection/refraction seismic profiles (with a total length of ∼1700 km) and near-vertical reflection seismic profiles (with a total length of ∼340 km) across the Dabie Orogen, eastern China have been completed in recent years, and allow the Moho depth and uppermost-mantle velocity to be mapped across ∼40,000 km 2 . These data reveal the detailed structure of the crust and upper mantle of this orogen that resulted from collision of the North China craton (NCC) with the Yangtze Craton (YC). The Dabie Orogen is an asymmetric orogen, with a thin crustal root (∼6 km) preserved in its northern part, highlighted by a north-dipping Moho. Compared to the nearly seismically-transparent lower crust, the Moho crust-mantle transition zone under the Dabie Orogen is a prominent north-dipping, strongly layered reflection, which is inferred to reflect the remnants of subduction of YC under the edge of the NCC or post-collisional exhumation of ultrahigh-pressure (UHP) rocks, and indicates the northward polarity of subduction of the YC. The Moho of the YC and NCC meet beneath the northern part of the Dabie Mountains, and the NCC Moho (north) is uplifted by ∼4 to 5 km (Offset 1) over the YC Moho (south), marking the NCC-YC collision zone. Along the southern margin of the Dabie Mountains, the Moho below the Yangtze foreland is underthrust beneath the Moho of the Dabie Mountains, forming another Moho overlap (Offset 2) with a depth difference of 5 to 6 km. The two Moho overlaps (offsets) at both flanks of the Dabie Mountains formed two crustal-scale boundaries at depth between the NCC and the Dabie Orogen, and the Dabie Orogen and the YC respectively. Offset 1 is considered to be the Triassic suture between the YC and NCC as supported by the metamorphic ages of UHP rocks. This displays a wedge-shaped offset zone opening towards the east that acted as a channel for exhumation of UHP rocks. Offset 2 under the southern margin of the Dabie Orogen is connected to the Xiangfan-Guangji fault that gave rise to a large-scale thrust detachment that propagated towards the foreland of the Dabie Orogen during the Jurassic. Thus our Moho mapping confirms that there are structural remnants of the Triassic deep continental subduction preserved, despite the superimposed Jurassic deformation.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Nonlinear Time Series Analysis.

Abstract: : This thesis applies neural network feature selection techniques to multivariate time series data to improve prediction of a target time series. Two approaches to feature selection are used. First, a subset enumeration method is used to determine which financial indicators are most useful for aiding in prediction of the S&P 500 futures daily price. The candidate indicators evaluated include RSI, Stochastics and several moving averages. Results indicate that the Stochastics and RSI indicators result in better prediction results than the moving averages. The second approach to feature selection is calculation of individual saliency metrics. A new decision boundary-based individual saliency metric, and a classifier independent saliency metric are developed and tested. Ruck's saliency metric, the decision boundary based saliency metric, and the classifier independent saliency metric are compared for a data set consisting of the RSI and Stochastics indicators as well as delayed closing price values. The decision based metric and the Ruck metric results are similar, but the classifier independent metric agrees with neither of the other metrics. The nine most salient features, determined by the decision boundary based metric, are used to train a neural network and the results are presented and compared to other published results. (AN)