Browsing by Author "Wang, Lu"
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- Cure Rate Model with Spline Estimated ComponentsWang, Lu (Virginia Tech, 2010-07-13)In some survival analysis of medical studies, there are often long term survivors who can be considered as permanently cured. The goals in these studies are to estimate the cure probability of the whole population and the hazard rate of the noncured subpopulation. The existing methods for cure rate models have been limited to parametric and semiparametric models. More specifically, the hazard function part is estimated by parametric or semiparametric model where the effect of covariate takes a parametric form. And the cure rate part is often estimated by a parametric logistic regression model. We introduce a non-parametric model employing smoothing splines. It provides non-parametric smooth estimates for both hazard function and cure rate. By introducing a latent cure status variable, we implement the method using a smooth EM algorithm. Louis' formula for covariance estimation in an EM algorithm is generalized to yield point-wise confidence intervals for both functions. A simple model selection procedure based on the Kullback-Leibler geometry is derived for the proposed cure rate model. Numerical studies demonstrate excellent performance of the proposed method in estimation, inference and model selection. The application of the method is illustrated by the analysis of a melanoma study.
- A general Metal-Ion-Modification route for preparing hydrophobic paper and tableware from lignocellulose fibersNayanathara, R. M. Oshani; Leng, Weiqi; Liyanage, Senal D.; Wang, Xiang; Wang, Lu; Wang, Jinwu; Tian, Zhenhua; Pittman, Charles U.; Gwaltney, Steven R.; Zhang, Xuefeng (Elsevier, 2023-03)Inherent hydrophilicity and poor water resistance prevent using lignocellulosic materials as green plastic al- ternatives to fossil fuel-based plastics. Here, we report a facile metal-ion-modification (MIM) route, swelling with aqueous metal ion solutions, and drying to convert conventional hydrophilic paper and wood pulp into biode- gradable hydrophobic paper and tableware without the addition of hydrophobic sizing chemicals/materials. Metal ions such as Fe3+ and Zr4+ can coordinate with pulp fibers' polar groups (i.e., OH, C-O, and COOH) that induce self-assembly of their surface fibrillated "hairy" cellulose nanofibrils to form a more compact structure with fewer available OH groups for water sorption. This decreases the surface energy of pulp fibers and increases their hydrophobicity and water resistance. Only similar to 3 mg of metal ions is needed to induce the wettability tran- sition in 1 g of kraft pulp, resulting in hydrophobic paper and tableware with water contact angles (WCAs) of 120-140 degrees. The coordinated Fe3+ and Zr4+ are stable, with negligible metal leaching during use, allowing the hydrophobic paper and tableware to be used for food packaging. This MIM technique can be integrated into the existing paper-making process for the scalable production of hydrophobic papers and tableware, providing an alternative route for developing sustainable and biodegradable plastic counterparts.
- Volumetric Transparency: Application of an Improved Double Glass Facade System to Cowgill Hall, BlacksburgWang, Lu (Virginia Tech, 2002-08-21)The initial idea for this thesis involved the design of an addition to Cowgill Hall on the Virginia Tech Campus in Blacksburg, Virginia. This addition, to be constructed with an envelope comprised primarily of glass, would be located on the south side of Cowgill Hall, adjacent to Cowgill Plaza. The all-glass box would add a transparent volume to the existing building, diminishing the barrier between inside and outside. The project would also energize the existing plaza by connecting the activity inside to outside and providing the dynamic reflection of a glass facade. Cowgill Hall would also be given new life by providing a new shared vertical space for dynamic communication and light. Potential problems associated with the all-glass box include high heat loss or gain, glare and noise control. A double envelope system of construction was explored as a means of solving some of these problems and an endeavor on literature review, technical research and design improvement of double glass facade was also made.