Statistical Methodology Commons^™

Exploring Latent Mediation Through Bayesian Regularization Methods Of Lasso, Ridge, Horseshoe, Spike-And-Slab, Ethan Harris

Graduate Theses and Dissertations

Regularization is a powerful tool to combat overfitting and drive sparsity in complex models. Regularization was initially applied in regression modeling but has been increasingly utilized in structural equation modeling where its utility in identifying the essential components has helped improve modeling. As structural equation models have increased in complexity both in the number of indicators but also the number of latent factors, researchers have begun to investigate how applying Bayesian regularization to these systems can further push the limits on modeling complex models with limited sample sizes. One area where research is limited is the application of Bayesian regularizations …

Innovative Methods For The Design And Analysis Of Phase Ii Clinical Trials, Feng Tian

Dissertations and Theses (Open Access)

Drug development has become increasingly time-consuming, costly, and risky in recent years. There is significant potential for improving clinical trial designs, particularly for phase II trials, which play a critical role in the drug development process. Innovative methods are especially necessary for addressing key challenges in phase II trials in terms of dose-ranging study, patient population selection, and decentralized clinical trials (DCTs). This dissertation presents a comprehensive set of methodologies that address these critical issues with three projects. The first project introduces a Bayesian adaptive dose-ranging design that integrates both efficacy and toxicity data to evaluate each dose comprehensively. The …

A Text Mining And Sentiment Analysis Of Valuable Cie Texts Using R, Eric Sugarman, Ethan Turber-Ortiz, Hannah Quinn

Mathematics, Computer Science & Statistics Presentations

The purpose of this project was to perform a sentiment analysis of three texts used in Ursinus College's Common Intellectual Experience (CIE) course: Between the World and Me by Ta-Nehisi Coates, The New Jim Crow by Michelle Alexander and Discourse on Method by Rene Descartes. Word count and word cloud analysis were also performed on the texts as well as term frequency and bigram analysis.

Statistical Study Of Solar Wind Conditions Prior To Substorm Onsets, Luke H. Francis

Doctoral Dissertations and Master's Theses

Due to complex, multi-region, coupled plasma systems, auroral substorm onsets have been historically difficult to predict. The northward turning of the interplanetary magnetic field was considered the primary candidate as an external triggering mechanism for substorm onsets. However, that was later shown to be coincidental in nature. This study is motivated by recent multi-spacecraft observations that show how several magnetosheath jets at the bow shock were heavily correlated to substorm onsets, indicated by a strongly radial IMF interval. In the past, studies have looked at small samples of substorms in order to make large-scale predictions. However in this study, a …

Robust Spacecraft Autonomy For Deep Space Exploration In Special Euclidean Group Se(3), Matthew Wittal

Doctoral Dissertations and Master's Theses

Over the past half-century, humanity has gained extensive experience conducting manned spaceflight near Earth. Arguably, "near Earth" could even include the Moon — the most distant destination humans have reached. However, "near" in this work primarily refers low Earth orbit (LEO). One could argue that we have not truly left Earth since the Apollo, as spacecraft in some LEOs remain subject to atmospheric drag thus emphasizing their continued connection to Earth's immediate environment. Reflecting on this, it becomes clear that humanity has largely remained bound to Earth’s immediate vicinity since the Apollo missions reached the Moon. However, that is set …

Quaternary Subsurface Characterization Of The Mississippi River Valley Alluvial Aquifer: Insights From Interval Kriging And Airborne Em-Borehole Data Integration, Yuqi Song

LSU Doctoral Dissertations

The Pleistocene period significantly contributed to the formation of alluvial aquifer worldwide. These productive aquifers are crucial for domestic, industrial, and agricultural water supplies. The Mississippi River Valley alluvial aquifer (MRVA), a principal aquifer in the U.S., is crucial for national food security and global agricultural supply. This study aims to characterize the subsurface architecture of the MRVA, thereby enhancing fundamental understanding of sedimentological processes involved in the genesis of glacio-fluvial aquifers worldwide. The research objectives are threefold: (1) to provide a detailed characterization of the MRVA; (2) to develop 3D geostatistical methods for geological modeling; and (3) to develop …

Bayesian Nonparametric Hypothesis Testing Methods On Multiple Comparisons, Qiuchen Hai, Zhuanzhuan Ma

School of Mathematical & Statistical Sciences Faculty Publications

In this paper, we introduce Bayesian testing procedures based on the Bayes factor to compare the means across multiple populations in classical nonparametric contexts. The proposed Bayesian methods are designed to maximize the probability of rejecting the null hypothesis when the Bayes factor exceeds a specified evidence threshold. It is shown that these procedures have straightforward closed-form expressions based on classical nonparametric test statistics and their corresponding critical values, allowing for easy computation. We also demonstrate that they effectively control Type I error and enable researchers to make consistent decisions aligned with both frequentist and Bayesian approaches, provided that the …

Discounting Effect Size When Borrowing External Data In Clinical Studies, Zhuanzhuan Ma, Chul Ahn, Bin Wang, Xuefeng Li

Research Symposium

Background: When borrowing information from external data to augment a current trial, many available methods discount the sample size but retain the effect size from previous studies. Discounting the sample size is just one way to discount the prior information. It may not be appropriate if the underlying assumption of unbiased treatment effect does not hold, for example, when the treatment effect in the historical study is likely higher than the one expected in the current trial.

Methods: To tackle this potential issue, we study some methods to shrink the effect size from previous studies assuming that the prior effect …

Sparse Bayesian Variable Selection Using Global-Local Shrinkage Priors For The Analysis Of Cancer Datasets, Zhuanzhuan Ma

Research Symposium

Background: With a rapid development of data collection technology, high dimensional data, whose model dimension k may be growing or much larger than the sample size n, is becoming increasingly prevalent in different fields of study, such as ecology, genetics, among others. This data deluge is introducing new challenges to traditional statistical procedures and theories and is thus generating a renewed interest in the problems of variable selection and classification in high dimensional regression models. In large k, small n settings, variable selection is usually the first step for dimension reduction to uncover significant covariates, which contribute to …

Leveraging Bayesian And Classical Techniques For Survival Analysis Using The Weibull-Rayleigh Distribution, Mahmoud Mansour, Rashad El-Sagheer, Nagwa Mohamed

Basic Science Engineering

This paper contributes to an extensive analysis of the Weibull-Rayleigh distribution (WRD), including Bayesian inference for randomly censored data. The WRD is a versatile model that fits various types of survival data, especially in situations including censoring, commonly found in biostatistics and engineering reliability research. The research investigates the derivation of the WRD’s probability density and cumulative distribution functions, employing maximum likelihood estimation (MLE) and Bayesian estimating techniques to accurately infer parameters. Gamma priors are utilized in Bayesian analysis, and approximate Bayesian estimates are derived by Gibbs sampling and Lindley’s approximation methods. An actual dataset that represents leukemia-free survival times …

Static Performance And Stability Of A Multi-Span Hybrid Continuous Rigid Frame Bridge With High Piers, Huang Yu, Liu Guanyu, Yi Jianbo, Xing Xuan, Su Miao, Peng Hui

Journal of China & Foreign Highway

In order to study the static performance and stability of a steel-concrete composite continuous rigid frame bridge in Suichang,Zhejiang Province,a single girder and girder lattice finite element model for the whole bridge was established by using Midas Civil,and a local solid finite element model was established by using Ansys.A detailed analysis of the structural displacement and stress state of the bridge in use and the local stress in the solid section of the pier and girder under different loads was carried out.The influence of the pile-bottom restraint stiffness and pier-girder connection form on the overall stability of the bridge was …

Influence Of Train Speed On Thermal Insulation And Anti-Thawing Length For Tunnel In Cold Region, Huang Huanan, Chen Yong, Wang Yibo, Wu Yaping

Journal of China & Foreign Highway

To study the influence of train speed on thermal insulation and anti-thawing measures for surrounding rock of tunnels in cold regions,it is necessary to analyze the temperature field.By using the Kunlun Mountain Tunnel Project in cold regions as a case study,the effects of external atmospheric temperature,piston wind effects caused by varying train speeds,and the driving resistance on the distribution of the tunnel ’s internal temperature field were considered.A three-dimensional numerical calculation model including the surrounding rock,concrete lining,and tunnel air was established by utilizing the thermo-fluid-structure interaction (TFSI ) technique.The thermal environment variations caused by trains at different speeds were predicted.The …

Parametric Analysis Of Composite Slab With Steel Bar Trusses At Construction Stages, Zhang Junhao, He Jun, Tan Chao, Feng Sidong, Wang Zitong

Journal of China & Foreign Highway

To clarify the structural behavior of composite slab with steel bar trusses at key construction stages including hoisting and concrete post-pouring,a composite beam bridge with a main span of 60 m in Georgia ’s E60 Highway was investigated.A finite element model was developed by using ABAQUS to simulate the construction process and analyze the influence of parameters such as prefabricated bottom slab material,number of hoisting points,slab thickness,and number of steel bar trusses on the principal stress of concrete and mid-span deflection.The results indicate that ultra-high-performance concrete (UHPC ) prefabricated bottom slabs prevent plastic damage and enhance slab stiffness.Normal concrete (NC) …

Cracking Characteristics Of Cement-Stabilized Macadam With Early Strength Agent Under Variable Temperature And Humidity Curing Conditions, Ge Dongdong, Liu Dingyuan, Lyu Songtao, Jiang Xiangyang, Xue Yanhua, Yu Yang

Journal of China & Foreign Highway

In environments with large temperature variations and low humidity,the curing conditions of cement-stabilized macadam fail to meet the specifications,leading to slow early strength development and increased susceptibility to cracking.This study aimed to investigate the effects of actual environmental temperature,humidity,curing age,and addition of early strength agents on the cracking characteristics of cement-stabilized macadam.Variable temperature conditions were determined based on actual environmental temperature data.Four curing conditions were set by combining temperatures (variable temperature and standard temperature ) with relative humidity of 95%,80%,and 65%,respectively.Three types of specimens were prepared with 0%,10%,and 15% early strength agent contents and cured for 14 and 28 days,respectively.The …

Identification And Prediction Model For Traffic Blockage State Of Highways To Xizang, Wu Ling, Liu Jianbei, Zhang Zhiwei, Shan Donghui, Chi Gandu

Journal of China & Foreign Highway

To identify the traffic blockage state on highways to Xizang in extreme environments,comprehensive evaluation indicators for traffic blockage state based on the entropy-weighted TOPSIS method were proposed by using the traffic blockage event parameters observed on four major highways to Xizang:Sichuan ‒ Xizang Highway,Yunnan ‒ Xizang Highway,Qinghai ‒ Xizang Highway,and Xinjiang ‒ Xizang Highway.The K-Medoids clustering algorithm was used to categorize the traffic blockage state into different levels.By considering factors such as hazard types,road types,traffic volume,and vehicle type ratios,a classification model for the traffic blockage state on highways to Xizang was constructed based on machine learning algorithms.The results show that …

Seismic Performance Of Bridge Pile Foundation Considering Effects Of Material Freeze-Thaw Deterioration And Permafrost Degradation, Zhang Xiyin, Yu Shengsheng, Wang Wanping, Wen Hairong

Journal of China & Foreign Highway

In cold and high-seismic regions,such as the Qinghai‒Xizang Plateau in China,the deterioration of material properties caused by freeze-thaw cycles and permafrost degradation due to climate change have become increasingly severe,posing significant challenges for the seismic performance assessment of bridge pile foundations.To systematically investigate the impact of permafrost degradation and material freeze-thaw deterioration on the seismic performance of bridge pile foundations and ensure proper seismic design,a finite element model was established,considering the dual effects of permafrost degradation and material freeze-thaw deterioration.A comparative analysis was conducted to evaluate the influence mechanisms of various factors on the seismic performance of bridge pile foundations …

Design And Simulation Evaluation Of Converged Toll Collection Schemes For Senegalese Highways, Lai Zengcheng, Zhang Ning, Yang Shichun, Ding Xueqi, Ji Yanjie

Journal of China & Foreign Highway

The Senegalese highway toll collection system is inefficient,and significant congestion and delays frequently occur at toll stations in the face of sudden traffic surges during holidays.This paper examined the limitations of the existing toll collection methods on Senegalese highways and combined the image detection algorithm and electronic license plate recognition technology with the existing MTC and ETC toll collection methods to construct a converged toll collection method based on vehicle information recognition.The paper aimed to optimize the Senegalese highway toll collection system,reduce its cost of use,and improve the efficiency of toll collection.The BPV Thiès toll station in Senegal was selected …

Model Test On Bearing Capacity Of Gravity Anchor Foundation Considering Rock Socketed Effect, Yin Jingze, Guo Chao, Zhang Xinmin, Li Wei, Shi Haiyang, Fu Baiyong

Journal of China & Foreign Highway

The calculation of the bearing capacity of traditional gravity anchor foundation instructed by Code for Design of Ground Base and Foundation of Highway Bridges and Culverts (JTG D 63—2007 ) only considers the friction effects of the basement and neglects the rock socketed effect of bottom plate,which is simply regarded as a safety margin,on the improvement of bearing capacity.To study the influence of rock socketed effect on the bearing capacity of gravity anchor,this paper designed two groups of indoor scale model tests on non-rock-socketed and rock-socketed gravity anchors with a scale of 1∶50 to discuss the bearing capacity and load …

Theoretical And Experimental Studies On Adaptive Spatial Rotating Main Cable Saddle, Chen Yuanlin, Huang Anming, Chen Long, Xie Jun

Journal of China & Foreign Highway

To ensure the accuracy of the main cable alignment during adaptive rotation,an adaptive spatial rotating main cable saddle suitable for spatial suspension bridges was designed.The main cable saddle had two adaptive rotating pair mechanisms with axes passing through the IP point.By using a specific suspension bridge as a case study,the design was validated through a combination of finite element analysis and model testing to assess the reliability and structural safety of the adaptive rotation mechanism.The results show that the adaptive spatial rotating main cable saddle can automatically adjust its orientation based on variations in the main cable load during construction,with …

Section Form Of Open-Cut Tunnel By Ultra-Large-Diameter Shield Empty-Push Technology, Sun Chao, Zhang Guangwei

Journal of China & Foreign Highway

Based on the engineering background of the open-cut section by the shield machine with overall movement in the rapid transformation project of Wanghai Road,Shenzhen City,the structural stress and economy of three types of section forms under construction and operation conditions were analyzed to determine the optimal section design.The load-structure model was used to analyze the parameters affecting the internal force of the optimal section.The research results show that the top and bottom plates and side walls in the scheme with ribs set at the corner (scheme 3) have uniform force,and force during the construction period is close to that during …