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Your search keyword '"Wang, Longlin"' showing total 29 results
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29 results on '"Wang, Longlin"'

1. A Comparison of Hamming Errors of Representative Variable Selection Methods

Author

Ke, Zheng Tracy and Wang, Longlin

Subjects
Mathematics - Statistics Theory
Abstract

Lasso is a celebrated method for variable selection in linear models, but it faces challenges when the variables are moderately or strongly correlated. This motivates alternative approaches such as using a non-convex penalty, adding a ridge regularization, or conducting a post-Lasso thresholding. In this paper, we compare Lasso with 5 other methods: Elastic net, SCAD, forward selection, thresholded Lasso, and forward backward selection. We measure their performances theoretically by the expected Hamming error, assuming that the regression coefficients are iid drawn from a two-point mixture and that the Gram matrix is block-wise diagonal. By deriving the rates of convergence of Hamming errors and the phase diagrams, we obtain useful conclusions about the pros and cons of different methods., Comment: 87 pages; 13 figures

Published
2022

4. Learning and Optimization with Seasonal Patterns

Author

Chen, Ningyuan, Wang, Chun, and Wang, Longlin

Subjects
Computer Science - Machine Learning, Statistics - Machine Learning
Abstract

A standard assumption adopted in the multi-armed bandit (MAB) framework is that the mean rewards are constant over time. This assumption can be restrictive in the business world as decision-makers often face an evolving environment where the mean rewards are time-varying. In this paper, we consider a non-stationary MAB model with $K$ arms whose mean rewards vary over time in a periodic manner. The unknown periods can be different across arms and scale with the length of the horizon $T$ polynomially. We propose a two-stage policy that combines the Fourier analysis with a confidence-bound-based learning procedure to learn the periods and minimize the regret. In stage one, the policy correctly estimates the periods of all arms with high probability. In stage two, the policy explores the periodic mean rewards of arms using the periods estimated in stage one and exploits the optimal arm in the long run. We show that our learning policy incurs a regret upper bound $\tilde{O}(\sqrt{T\sum_{k=1}^K T_k})$ where $T_k$ is the period of arm $k$. Moreover, we establish a general lower bound $\Omega(\sqrt{T\max_{k}\{ T_k\}})$ for any policy. Therefore, our policy is near-optimal up to a factor of $\sqrt{K}$.

Published
2020

5. A Practical Approach to Alignment and Error Feedback Control for Long-Span Arch Bridges.

Author

Yao, Xinyu, Li, Chuanxi, Wang, Longlin, Yu, Mengsheng, Zhuo, Xiaoli, Hao, Tianzhi, and Wang, Xirui

Subjects
ARCH bridges, LONG-span bridges, ARCHES, UNIFORMITY, CABLES, METASTASIS
Abstract

The accurate installation of long-span arch bridges' arch ribs remains a challenge due to the complex calculations required for cable forces and arch rib displacements, as well as the significant influence of environmental and construction loads. In this study, we propose a practical approach to alignment and error feedback control for long-span arch bridges. Cable forces were optimized using multiple control objectives based on influence matrix principles. The impact of temperature on the next segment to be installed was analyzed using the metastatic GM(1, 1) model and fitting results. Several tunable parameters were employed to account for parameter errors and environmental interference. These parameters were adjusted based on the deviations between practical and theoretical alignments for different arch rib segments, achieving a model output of an offset-free-tracking arch rib structure. This technology was applied to monitor the construction of the Tian'e Longtan Grand Bridge. Compared to conventional alignment control approaches, the proposed method achieved excellent arch ring alignment after the closure of the high-accuracy arch rib and cable release, as well as effective control of cable force uniformity and tower deviation. Field measurement data indicate that the closing deviation of the arch ring is only 3 mm. This study provides a valuable reference for the construction control of long-span arch bridges. [ABSTRACT FROM AUTHOR]

Published
2024
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28. Study on the Monitoring Method of Windinduced Response of Transmission Tower Structure Based on Dynamic Analysis

Author

Wang Hailong, Luo Yuejing, Deng Nianchun, and Wang Longlin

Subjects
Vibration, Wind power, business.industry, Typhoon, Environmental science, business, Tower, Physics::Atmospheric and Oceanic Physics, Wind engineering, Wind speed, Finite element method, Transmission tower, Marine engineering
Abstract

It is important to study the wind disaster reduction method of transmission tower structure in typhoon prone coastal areas. In order to ensure the safety of the transmission tower structure and its power line under the typhoon wind load, it is proposed that the transmission tower structure should be monitored using bridge health monitoring method. The monitoring items including the wind power, wind speed and dynamic response of tower structure. Firstly, the finite element model of transmission tower structure system was built to make the dynamic and time history analysis under the simulated typhoon wind load; Secondly, with the result from analysis, the vibration acceleration, vibration displacement and time history curve of each part of the tower are analyzed, and the dynamic response rule of the tower under the action of vector wind load is obtained. Based on the finite element analysis results, the parts which had the large dynamic response are selected to arrange as measuring points of tower structure. The selection method of monitoring sensor is proposed according to the dynamic monitoring requirements. At last the wind monitoring system of transmission tower was presented. In the typhoon prone season, the dynamic monitoring system can be used to collect real-time response data of the tower, which can provide the basic data for the study of the wind disaster reduction for tower structure.

Published
2017

29. Vehicle–Bridge Coupling Vibration of Long-Span Concrete-Filled Steel Tubular Arch Bridge.

Author

Yu, Peng, Yu, Cun, Ren, Zhaoyong, and Wang, Longlin

Abstract

An increase in the nonlinearity of the bridge will lead to a more obvious vehicle–bridge interaction effect and affect the vehicle response and driving comfort as the span increases. This paper establishes a refined finite element model of vehicle–bridge coupling for the 575 m long-span concrete-filled steel tubular arch bridge, Pingnan Third Bridge. Coupling vibration responses under different vehicle speeds, vehicle weights and road conditions of this bridge is analyzed. Then its comfort is assessed according to the comfort criterion. The results show that the vehicle–bridge coupling model has good agreement with the field test. The dynamic response of the bridge within the speed limit has no significant linear relationship with the magnitude of the vehicle speed without considering the pavement class. When the vehicle exceeds the speed limit, the dynamic response increases sharply with the increase in speed. The increase in vehicle weight leads to an increase in the maximum dynamic deflection of the bridge and a decrease in the impact coefficient, but the actual total response of the bridge does not decrease. The worse the road surface condition, the more dramatic the dynamic response of the bridge structure, taking into account the road surface level. [ABSTRACT FROM AUTHOR]

Published
2024
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