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.

A deep seismic sounding profile across the Tianshan Mountains

Abstract: The deep seismic sounding profile across the Tianshan Mountains revealed a two-layer crustal structure in the Tianshan region, namely the lower and upper crusts. Lateral variations of layer velocity and thickness are evidently shown. Low-velocity layers spread discontinuously at the bottom of the upper crust. The Mono depth is 47 km in the Kuytun area and 50 km in the Xayar area. In the Tianshan Mountains, the Moho becomes deeper with the maximum depth of 62 km around the boundary between the southern and northern Tianshan Mountains. The average velocity ranges from 6.1 to 6.3 km/s in the crust and 8.15 km/s at the top of the upper mantle. Two groups of reliable reflective seismic phases of the Moho (Pm1 and Pm2) are recognized on the shot record section of the Kuytun area. A staked and offset region, 20–30 km long, is displayed within a shot-geophone distance of 190–210 km in Pm1 and Pm2. Calculation shows that the Moho is offset by 10 km in the northern Tianshan region, 62 km deep in the south while 52 km deep in the north, and plunges northwards. In comparison with typical collisional orogenic belts, the structure of the Moho beneath the Tianshan Mountains presents a similar pattern. This can be used to explain the subduction of the Tarim plate towards the Tianshan Mountains. This intracontinental subduction is considered the dynamic mechanism of the Cenozoic uplifting of the Tianshan Mountains. The discovery of seismic phases Pm1 and Pm2 serves as the seismological evidence for the northward subduction of the Tarim plate.

Turbulence effects on surface pressures of rectangular cylinders

Abstract: This paper presents the effects of free-stream turbulence on streamwise surface pressure fluctuations on two-dimensional rectangular cylinders. Particular attention is given to possible effects of turbulence integral scale on fluctuation and peak pressures. The mean, standard deviation, peak pressure coefficients, spectra and cross-correlation of fluctuating pressures were measured to investigate the nature of the separation and reattachment phenomenon in turbulent flows over a wide range of turbulence intensity and integral scale.

Equivalent Static Wind Loads on Long-Span Roof Structures

Abstract: The loads on buildings and structures caused by the buffeting action of wind have traditionally been analyzed using the gust loading factor (GLF) approach in most codes and standards. In the GLF approach, the equivalent static wind load (ESWL) for structural design is equal to the mean wind force multiplied by the GLF. However, this method fails to provide meaningful guidance in cases with zero mean response. This paper presents a new description of the ESWLs on long-span roof structures based on the load-response-correlation approach, which eliminates the shortcoming of the GLF. The ESWL for a given peak displacement response is expressed in terms of the mean and dynamic components; and the wind loading inputs are determined based on wind tunnel test results of multiple point pressure measurements on rigid structural models. It is noteworthy that in the proposed approach the total dynamic response is directly calculated by the complete quadratic combination approach, in which there is no need to separate the response into the background and resonant components and meanwhile the contributions of multimode response and modal response correlations are taken into consideration. Moreover, unlike existing approaches, it is not required to calculate the correlation of the load and the response, which is difficult to determine by conventional methods. Finally, an extra-long-span roof structure, which is the world's longest spatial lattice structure, is considered to illustrate the determination of the ESWLs by the proposed approach and to demonstrate its effectiveness in the design and analysis of long-span roof structures. It is shown through an example that the proposed approach can be used in conjunction with wind tunnel tests in predicting the response components not directly measured from the model tests and providing the design loads accurately.

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)