Simulation-Based Evaluation and Optimization of the Seismic Performance of Buildings with Passive Energy Dissipation System

Earthquakes are one of the major natural hazards that could directly cause damages to or collapse of buildings, leading to significant economic losses. In this dissertation research, analytical tools and simulation-based optimization framework are developed to improve our understanding of and the ability to design more seismic-resilient structures with passive energy dissipation systems. The main objectives of this dissertation are to (1) investigate the seismic performance of structures with energy dissipation systems and evaluate the effectiveness of damping coefficient dissipation methods using three-dimensional numerical models; (2) develop a simulation-based multi-objective optimization framework to evaluate and optimize the seismic performance of buildings with energy dissipation systems; (3) incorporate and evaluate the influence of soil-structure interaction in the performance-based seismic design of structures. Aiming at these objectives, this dissertation consists of three related studies. In the first study, the seismic performance of structures with energy dissipation systems, specifically fluid viscous dampers (FVD), was investigated using three-dimensional (3D) numerical models. Four different damping coefficient distribution methods for FVD were extended to 3D numerical models. Then, their effectiveness in terms of improving structural seismic performance was evaluated through a series of nonlinear dynamic analysis. The seismic performance of the structure has been significantly improved by applying the FVD, and this significance of the improvement depends on the distribution of damper\u27s damping coefficient within the 3d numerical model. Among the four different damping coefficient distribution methods, the story shear strain energy distribution (SSSED) method was found to be an optimal distribution method that can improve the inter-story drift of the structure while it can also provide the most uniformly distributed inter-story drift. In the second study, a performance-based optimization framework for the structural design was developed that considers multiple conflicting objectives: initial material cost, structural repair cost, and record-to-record variability of ground motions. The developed optimization framework was effective in improving the seismic performance of structures. All obtained optimum designs can dramatically decrease the inter-story drift and peak floor acceleration of the structure. This study also provided a practical approach to select the optimal design variables of the energy dissipation systems. The selected design can achieve the desired performance level of the structure with moderate initial material cost, structural repair cost, and robustness measure. In the third study, the effect of soil-structure interaction was incorporated into the optimization framework developed in the second study. Two scenarios were considered in the analysis: one with a fixed foundation, and the other one with a flexible foundation. In this study, the selection of soil properties was based on site class D. The frame with a flexible foundation was found to have a larger inter-story drift in each floor when compared to the frame with a fixed foundation. The guideline for selecting the best-performance design was developed based on the inter-story drift ratio. The improvement of the inter-story drift (compared to a bare frame without energy dissipation systems) and the uniformity of the inter-story drift, were proposed as two performance indices to evaluate the effectiveness of the selected designs. Finally, based on findings of this dissertation work, recommendations for seismic design of buildings with energy dissipation systems and directions for future research are given

Tourists' Attitudes Towards Tea Tourism: A Case Study in Xinyang, China

Tea tourism as a new niche market has become more and more popular. Through a case study in Xinyang, China, this research explores tourists' attitudes and perceptions toward tea and tea tourism, identifies who the potential tea tourists are, and compares their attitudes with others. One hundred seventy-nine questionnaires were administered; one-way ANOVA and chi-square test were used based on their willingness of tea tourism. The results suggest that tea tourists and non-tea tourists have significant differences in terms of their attitudes toward tea drinking and their willingness of buying tea as souvenir. Tea tourists are mainly tea lovers driven by their high interest in tea and tea culture; they tend to be both males and females (yet females show a significant higher percentage than males), between ages 31-40, who have a positive attitude toward tea drinking, and who often drink tea. This research also provides some marketing suggestions for this niche market

Interactive Causal Correlation Space Reshape for Multi-Label Classification

Most existing multi-label classification models focus on distance metrics and feature spare strategies to extract specific features of labels. Those models use the cosine similarity to construct the label correlation matrix to constraint solution space, and then mine the latent semantic information of the label space. However, the label correlation matrix is usually directly added to the model, which ignores the interactive causality of the correlation between the labels. Considering the label-specific features based on the distance method merely may have the problem of distance measurement failure in the high-dimensional space, while based on the sparse weight matrix method may cause the problem that parameter is dependent on manual selection. Eventually, this leads to poor classifier performance. In addition, it is considered that logical labels cannot describe the importance of different labels and cannot fully express semantic information. Based on these, we propose an Interactive Causal Correlation Space Reshape for Multi-Label Classification (CCSRMC) algorithm. Firstly, the algorithm constructs the label propagation matrix using characteristic that similar instances can be linearly represented by each other. Secondly, label co-occurrence matrix is constructed by combining the conditional probability test method, which is based on the label propagation reshaping the label space to rich label semantics. Then the label co-occurrence matrix combines with the label correlation matrix to construct the label interactive causal correlation matrix to perform multi-label classification learning on the obtained numerical label matrix. Finally, the algorithm in this paper is compared with multiple advanced algorithms on multiple benchmark multi-label datasets. The results show that considering the interactive causal label correlation can reduce the redundant information in the model and improve the performance of the multi-label classifier

Changes in the neutrophil-to-lymphocyte and platelet-to-lymphocyte ratios before and after percutaneous coronary intervention and their impact on the prognosis of patients with acute coronary syndrome

OBJECTIVES: This study aimed to prospectively observe the changes in the neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) before and after percutaneous coronary intervention (PCI) and their impact on the prognosis of patients with acute coronary syndrome (ACS). METHODS: Blood samples from 205 patients with ACS were collected at admission and at 24h and 30 days postPCI to observe changes in the complete blood count. The Cox multivariate regression model was used to analyze the factors influencing major adverse cardiac events (MACE) after PCI in patients with ACS. A receiver operating characteristic (ROC) curve was used to evaluate the predictive value of inflammation indicators for MACE after PCI. RESULTS: Following PCI, NLR and PLR first increased postoperatively and then decreased within 30 days after PCI. Cox multivariate regression analysis showed that NLR and PLR at 24h post-PCI and acute ST-segment elevation myocardial infarction were independent influencing factors for the incidence of MACE after PCI. The ROC curve analysis showed that the NLR at 24h post-PCI was a better predictor of the incidence of MACE. The NLR at 24h post-PCI was significantly correlated with the number and length of implanted stents and operation duration. CONCLUSIONS: After PCI, patients with ACS had an increased neutrophil proportion and NLR. The NLR at 24h post-PCI was a better predictor of the incidence of postoperative MACE

The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: a tomographic analysis of structure growth and expansion rate from anisotropic galaxy clustering

We perform a tomographic analysis of structure growth and expansion rate from the anisotropic galaxy clustering of the combined sample of Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 12, which covers the redshift range of $0.2<z<0.75$. In order to extract the redshift information of anisotropic galaxy clustering, we analyse this data set in nine overlapping redshift slices in configuration space and perform the joint constraints on the parameters $(D_V, F_{\mathrm{AP}}, f\sigma_8)$ using the correlation function multipoles. The analysis pipeline is validated using the MultiDark-Patchy mock catalogues. We obtain a measurement precision of $1.5\%-2.9\%$ for $D_V$, $5.2\%-9\%$ for $F_{\mathrm{AP}}$ and $13.3\%-24\%$ for $f \sigma_8$, depending on the effective redshift of the slices. We report a joint measurement of $(D_V, F_{\mathrm{AP}}, f\sigma_8)$ with the full covariance matrix in nine redshift slices. We use our joint BAO and RSD measurement combined with external datasets to constrain the gravitational growth index $\gamma$, and find $\gamma=0.656 \pm 0.057$, which is consistent with the $\Lambda$CDM prediction within 95\% CL.Comment: 8 pages, 8 figures, 2 tables, accepted for publication MNRAS. The measured results including the full covariance matrices are made available at https://github.com/ytcosmo/TomoBAORSD and tomographic clustering data used in this work is available at https://sdss3.org//science/boss_publications.ph

Experimental study and modelling of average void fraction of gas-liquid two-phase flow in a helically coiled rectangular channel

Void fraction is an important parameter in designing and simulating the relevant gas-liquid two-phase flow equipment and systems. Although numerous experimental research and modelling of void fraction in straight circular channels have been conducted over the past decades, the experimental data and prediction methods for the average void fraction in helically coiled channels are limited and needed. Especially, there is no such information in helically coiled channels with rectangular cross section. Therefore, it is essential to advance the relevant knowledge through experiments and to develop the corresponding prediction methods in helically coiled rectangular channels. This paper presents experimental results of the average void fraction and new models for the void fraction in a horizontal helically coiled rectangular channel. First, experiments were conducted with air-water two-phase flow in the horizontal helically coiled rectangular channel at a wide range of test conditions: the liquid superficial velocity ranges from 0.11 to 2 m/s and the gas superficial velocity ranges from 0.18 to 16 m/s. The average void fractions were measured with a quick-closing valve (QCV) method. The measured void fraction ranges from 0.012 to 0.927 which cover four flow regimes including unsteady pulsating, bubbly, intermittent and annular flow observed with a high speed camera. Second, comparisons of the entire measured average void fraction data to 32 void fraction models and correlations were made. It shows a low accuracy of these models and correlations in predicting the experimental data for the void fraction smaller than 0.5 while the drift flux model of Dix (Woldesemayat and Ghajar, 2007) predicts 98.3% of the entire experimental data within ±10% for the void fraction larger than 0.5. Therefore, the Dix model is recommended for the void fraction larger than 0.5. Furthermore, the observed flow regimes in the coiled channels were compared to two mechanistic flow regime maps developed for horizontal straight circular tubes. The flow regime maps do not capture all flow regimes in the present study. Finally, the effects of the limiting affecting parameters on the void fraction models are analyzed according to the physical phenomena and mechanisms. Incorporating the main affecting parameters, new void fraction models have been proposed for the void fractions in the ranges of 0 < α ≤ 0.2 and 0.2 < α ≤ 0.5 respectively according to the slip flow model. Both models predict the experimental data reasonably well. Overall, the new proposed models and the recommended model predict 92.8% of the entire void fraction data within ±30%

Fast Global Convergence of Natural Policy Gradient Methods with Entropy Regularization

Natural policy gradient (NPG) methods are among the most widely used policy optimization algorithms in contemporary reinforcement learning. This class of methods is often applied in conjunction with entropy regularization -- an algorithmic scheme that encourages exploration -- and is closely related to soft policy iteration and trust region policy optimization. Despite the empirical success, the theoretical underpinnings for NPG methods remain limited even for the tabular setting. This paper develops $\textit{non-asymptotic}$ convergence guarantees for entropy-regularized NPG methods under softmax parameterization, focusing on discounted Markov decision processes (MDPs). Assuming access to exact policy evaluation, we demonstrate that the algorithm converges linearly -- or even quadratically once it enters a local region around the optimal policy -- when computing optimal value functions of the regularized MDP. Moreover, the algorithm is provably stable vis-\`a-vis inexactness of policy evaluation. Our convergence results accommodate a wide range of learning rates, and shed light upon the role of entropy regularization in enabling fast convergence.Comment: v2 adds new proofs and improved results; accepted to Operations Researc