23 research outputs found
Fast algorithms for Bayesian variable selection
No full textVariable selection of regression and classification models is an important but challenging problem. There are generally two approaches, one based on penalized likelihood, and the other based on Bayesian framework. We focus on the Bayesian framework in which a hierarchical prior is imposed on all unknown parameters including the unknown variable set. The Bayesian approach has many advantages, for example, we can access unknown obtain the posterior distribution of the sub-models. And more accurate prediction may be obtained by model averaging.
However, as the posterior distribution of the model parameters is usually not in closed form, posterior inference that relies on Markov Chain Monte Carlo (MCMC) has high computational cost especially in high-dimensional settings, which makes Bayesian approaches undesirable. In order to deal with datasets with large number of features, we aim to develop fast algorithms for Bayesian variable selection, which approximate the true posterior distribution, but yet still return the right inference (at least asymptotically).
In this thesis, we start with a variational algorithm for linear regression. Our algorithm is based on the work by Carbonetto and Stephens (2012), and with essential modifications including updating scheme and truncation of posterior inclusion probabilities. We have shown that our algorithm achieves both frequentist and Bayesian variable selection consistency.
Then we extend our variational algorithm to logistic regression by incorporating the Polya-Gamma data-augmentation trick (Polson et al., 2013), which links our algorithm for linear regression with logistic regression. However, as the variational algorithm needs to update the variational distribution of all the latent Polya-Gamma random variables of the same size of the observations at every iteration, this algorithm is slow when there are huge amount of observations, or even be infeasible when the data is too large to be loaded into computer memory. We propose an online algorithm for the logistic regression, under the framework of online convex optimization. Our algorithm is fast, and achieves similar accuracy (log-loss) as the state-of-art algorithm (Follow-the-Regularized-Proximal algorithm).Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2019-08-01The student, Xichen Huang, accepted the attached license on 2017-07-07 at 15:07.The student, Xichen Huang, submitted this Dissertation for approval on 2017-07-07 at 15:23.This Dissertation was approved for publication on 2017-07-10 at 12:40.DSpace SAF Submission Ingestion Package generated from Vireo submission #11339 on 2017-09-29 at 10:46:46Made available in DSpace on 2017-09-29T17:45:38Z (GMT). No. of bitstreams: 2
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Previous issue date: 2017-07-10Embargo set by: Colleen Fallaw for item 103486
Lift date: 2019-09-29T17:48:06Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 103486
Lift date: 2020-03-02T19:56:41Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 103486
Lift date: 2020-03-02T19:59:52Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 103486
Lift date: 2020-03-02T20:02:46Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Only Restriction Lifted for Item 103486 on 2020-03-03T10:15:29Z
Exploration of the Motion Graphics Educational tools based on the animations ‘Weddings’
No full textWith the development of science and technology, computer networks and smart devices are widely used in our life and strongly driving social growth, including the field of education. Cities are becoming bigger and bigger. People are getting busier in modern times. People have lots of free but short time slots every day, but attending traditional classes is limited by the factors of geographical location, distance, time, etc. Thus the demand for on-line meetings and remote learning is sharply increasing. People are seeking a convenient and effective method to gain knowledge or information with their fragment time. This thesis is under such a background and focuses on the exploration of the Motion Graphics Educational tools based on the animations ‘Weddings’.
This thesis project presents an applicable design solution to facilitate extensive online educational classes. The author designed a series of animations of weddings in two specific times as an Exploratorium attempt via motion graphics from four aspects, audio, time, graphics, and motion effects. This thesis describes the process discussion on the topics of design and the benefits based on these four factors. For further accessible cultural communication, the author set up a website of weddings to work as a public channel to display the animations to the audience. On purpose for better understand the benefits of motion graphic educational tools better and functional realization effectiveness of this project, the author conducted two surveys and analyzed the responses and confirmed the educational tools do work to convey the expected information to the audience.
This thesis project demonstrates how motion graphics are implicated as a useful educational tool based on the animations ‘Weddings.’ It creates a more learner-friendly and accessible manner for the audience to gain knowledge or information conveniently and efficiently
The Coupling of Strain and Lithium Diffusion: A Theoretical Model Based on First-Principles Calculations
No full textMost electrodes undergo volume changes in lithium-ion batteries, and it turns out that the volume changes also significantly affect lithium diffusion kinetics based on first-principles calculations. To study the mechano-electro-chemical coupling, a theoretical model of spherical electrode has been developed and the effect of strain on diffusion coefficient is explicitly considered. The results show that strain-enhanced diffusion greatly alleviates diffusion-induced stresses, and the lithiation and delithiation are extremely asymmetric in lithium concentration distribution and stresses due to asymmetrical changes of diffusion coefficient with time and positions along the radial direction. (C) 2015 The Electrochemical Society.National Natural Science Foundation of China [11172231, 11372241]; ARPA-E [DE-AR0000396]; AFOSR [FA9550-12-1-0159]SCI(E)[email protected]; [email protected]
An Optimization Model Applied to Active Solar Energy System for Buildings in Cold Plateau Area
No full textAbstractThe large-scale utilization of solar energy in buildings is one of the most promising technologies to solve the global energy shortage problem and reduce the carbon dioxide emissions. The present paper has proposed an optimization model coupled with solar thermal and photovoltaic systems. Optimization results of active solar energy system from the energy saving view and economical view have been obtained for typical hotel and office buildings in cold plateau area, respectively
Impact of Water Saving Policy on Water Resource and Economy for Hebei, China Based on an Improved Computable General Equilibrium Model
No full textHebei Province of China is facing a severe water resource shortage, making it urgent to formulate economical and effective water conservation policies. However, few studies have focused on analyzing the resource and economic impacts of a water policy. This study developed an improved computable general equilibrium (CGE) model with an extended water resources module as a policy analysis tool. The extended water resources module includes different water resources as commodities and water sectors, and introduces a substitution mechanism among the water resources. Policy scenarios containing different policy types and policy objects were established, including water price, technology (tech) improvement, structure adjustment, and water reuse policies in primary, secondary, and tertiary sectors. The impact on the water resource and economy of the scenarios was analyzed using the CGE model. The recommended policies include: an agricultural technology improvement policy that decreases groundwater usage by 240 hm3; an industrial technology improvement policy under which water usage per 10,000 CNY of industrial added value decreases by 13%; an industrial water reuse policy that increases unconventional water usage by 20%; and a structure adjustment policy to increase the proportion of the tertiary sector. The study provides an analysis tool for simulating and evaluating a water resource policy
Essays in empirical microeconomics
No full textIn my dissertation, I use tools in empirical microeconomics to study topics broadly related to public economics. In Chapter 1, I study the impact of recreational marijuana dispensaries on local crime in Chicago. The legalization of recreational marijuana dispensaries in many U.S. states has prompted debates about their potential social consequences. This paper examines the impact of recreational marijuana dispensaries on local crime in Chicago, Illinois. Utilizing the lottery-based issuance of dispensary licenses, I employ Difference-in-Difference estimators that account for heterogeneous treatment effects with differential timing. I show that the opening of a recreational marijuana dispensary in Chicago led to about a 30\% increase in crime within a 500-meter radius of the dispensary. This effect persists over time and is primarily associated with property crime and violent crime. Moreover, evidence suggests that this crime increase is driven by the relocation of crime from more distant areas to those in closer proximity to ds. I also identify heterogeneous effects across different demographic and socio-economic factors. Finally, I present evidence that census tracts may not be suitable units for analyzing the effects of ds, highlighting the importance of geographical granularity in such studies. Overall, this research reconciles conflicting findings in the existing literature by illustrating that the impact of ds on local crime is context-dependent.
In Chapter 2, I study the effects of dowries on female intra-household bargaining power and female welfare. I also study the effects of dowries on children human capital accumulation. I use a Chinese longitudinal dataset CFPS. To address endogeneity issues, I use an instrument that measures local dowry spending with respect to average household income. I find evidence that higher dowries lead to higher female household bargaining power and therefore better children education outcome. I find no evidence that higher dowries increase female mental and physical welling or children health.
In Chapter 3, I study the impact of the Paycheck Protection Program on employment in publicly traded companies. The COVID-19 pandemic caused unprecedented disruption of the U.S. labor markets, with rapid, record-setting increases in unemployment. The Paycheck Protection Program (PPP) was enacted as a response to counter the havoc. To date, over 800 billion dollars have been issued as low interest rate loans to small businesses and the majority of it has been forgiven. This paper tries to understand whether this enormous spending has achieved its goals of maintaining employment and whether it provide a good model for future policy responses to crisis. Linking compustat data on publicly traded firms with PPP loan data from Small Business Administration, I estimate an OLS model and a TWFE model. In both specifications I find no significant effect of PPP loans on employment, consistent with some previous literature.Ph.D.Includes bibliographical reference
The trans DNA cleavage activity of Cas12a provides no detectable immunity against plasmid or phage
No full textCas12a is a type V-A CRISPR-Cas RNA-guided endonuclease. It cleaves dsDNA at specific site, and then is activated for nonspecific ssDNA cleavage in trans in vitro. The immune function of the trans activity is still unknown. To address this question, we constructed a Cas12a targeting system in Escherichia coli, where Cas12a cleaved a high-copy target plasmid to unleash the trans ssDNA cleavage activity. Then, we analyzed the effect of the Cas12a targeting on a non-target plasmid and a ssDNA phage. The results show that Cas12a efficiently eliminates target plasmid but exerts no impact on the maintenance of the non-target plasmid or plague formation efficiency of the phage. In addition, a two-spacer CRISPR array, which facilitates target plasmid depletion, still has no detectable effect on the non-target plasmid or phage either. Together, the data suggest that the trans ssDNA cleavage of Cas12a does not contribute to immunity in vivo
Study on the Optimization of Wujiang’s Water Resources by Combining the Quota Method and NSGA-II Algorithm
No full textRecently, the Chinese government has implemented stringent water requirements based on the concept of ‘Basing four aspects on water resources’. However, existing research has inadequately addressed the constraints of water resources on population, city boundaries, land, and production, failing to adequately analyze the interplay between water resource limitations and urban development. Recognizing the interconnectedness between urban water use and economic development, a multi-objective model becomes crucial for optimizing urban water resources. This study establishes a nonlinear multi-objective water resources joint optimization model, aligning with the “Basing four aspects on water resources” requirement to maximize urban GDP and minimize total water use. A genetic algorithm (NSGA-II Algorithm) is applied to solve this complex nonlinear multi-objective model and obtain the Pareto solution set, addressing information loss inherent in the traditional water quota method. The model was tested in Wujiang District, an area located in China’s Jiangsu Province that has been rapidly urbanizing over the past few decades, and yielded 50 non-inferior water resource optimization schemes. The results reveal that the Pareto solution set visually illustrates the competition among objectives and comprehensively displays the interplay between water and urban development. The model takes a holistic approach to consider the relationships between water resources and urban population, land use, and industries, clearly presenting their intricate interdependencies. This study serves as a valuable reference for the rational optimization of water resources in urban development
