A 15 h ozonation was performed on bioremediated soil to remove recalcitrant residual oil. To monitor the survival of indigenous microorganisms in the soil during in-situ chemical oxidation(ISCO) culturing and a functional genearray, GeoChip, was used to examine the functional genes and structure of the microbial community during ozonation (0h, 2h, 4h, 6h, 10hand15h). Breakthrough ozonation decreased the population of cultivable heterotrophic bacteria by about 3 orders of magnitude. The total functional gene abundance and diversity decreased during ozonation, as the number of functional genes was reduced by 48percent after 15 h. However, functional genes were evenly distributed during ozonation as judged by the Shannon-Weaver Evenness index. A sharp decrease in gene number was observed in the first 6 h of ozonation followed by a slower decrease in the next 9 h, which was consistent with microbial populations measured by a culture based method. Functional genes involved in carbon, nitrogen, phosphors and sulfur cycling, metal resistance and organic remediation were detected in all samples. Though the pattern of gene categories detected was similar for all time points, hierarchica lcluster of all functional genes and major functional categories all showed a time-serial pattern. Bacteria, archaea and fungi decreased by 96.1percent, 95.1percent and 91.3percent, respectively, after 15 h ozonation. Delta proteobacteria, which were reduced by 94.3percent, showed the highest resistance to ozonation while Actinobacteria, reduced by 96.3percent, showed the lowest resistance. Microorganisms similar to Rhodothermus, Obesumbacterium, Staphylothermus, Gluconobacter, and Enterococcus were dominant at all time points. Functional genes related to petroleum degradation decreased 1~;;2 orders of magnitude. Most of the key functional genes were still detected after ozonation, allowing a rapid recovery of the microbial community after ozonation. While ozone had a large impact on the indigenous soil microorganisms, a fraction of the key functional gene-containing microorganisms survived during ozonation and kept the community functional.

As online shopping becomes to be popular, the recommender system in e-commerce sites is an increasingly popular business tool to increase sales. Researchers and industry practitioners are looking for all possible approaches to improve recommendation performance. Even a minor improvement could lead to a big business return.

Traditional approaches of recommender systems include content-based methods and collaborative filtering methods. For example, if a user viewed some cameras in the website, the system learns that the user is interested in cameras and recommends more similar items to the user. Yet it might not match with the user's true purchase intention. In real-world applications, recommender systems could leverage more information from the user, both information within a single session and information across sessions. To solve this problem, we propose to investigate the session-aware recommender system in e-commerce. Such system can understand a user's short-term goal and long-term preference, in order to recommend appropriate items accordingly.

We first explore how to integrate the complementary information (e.g. the user's purchase information, search information and so on) within a single session to build a textit{unified recommender system}. We analyze the available information for the unified model, including the user's history-related information, the search-related information and the product's marketing-related information. Three unified models are proposed and compared to integrate different pieces of information.

To go beyond making recommendations within a single session, we then study how to make better recommendations across sessions. To make recommendations based on a user's previous behavior in earlier sessions, we need to understand how users make purchase decisions across sessions. Earlier research in economics and marketing indicates that a consumer usually makes purchase decision(s) based on the product's marginal net utility (i.e., the marginal utility minus the product price). Utility is defined as the satisfaction or pleasure a user gets when purchasing the corresponding product. A rational consumer chooses the product to purchase in order to maximize the total net utility. To better match users' purchase decisions in the real world, we explore how to recommend products with the highest marginal net utility in e-commerce sites. Inspired by the Cobb-Douglas utility function in consumer behavior theory, we propose a novel utility-based recommendation framework. The framework can be utilized to revamp a family of existing recommendation algorithms.

To further incorporate the time interval between sessions into the system, we propose and study a new problem: how to recommend the right product at the right time? We adapt the proportional hazards model in survival analysis and propose the new opportunity model in e-commerce. The new model estimates the joint probability of a user making a follow-up purchase of a particular product at a particular time. This joint purchase probability can be leveraged by recommender systems in various scenarios, including a zero-query pull-based scenario or a proactive push-based email promotion scenario.

We evaluate the soundness of our models with multiple metrics. Experimental results with a real-world e-commerce website (shop.com) show that they have decent predictability of the user's purchase behavior within a session and across sessions. In addition, the models significantly improve the conversion rate in pull-based systems and the user satisfaction/utility in push-based systems.

In this dissertation, we first introduce the motivation of the work.

Secondly, we report some state-of-art related work of this topic.

Thirdly, models are proposed to tackle the problem, followed by the experimental results. Then we summarize our contribution in both the research field of recommender systems and the e-commerce domain.

Disorders and dissipations play the key role in the understanding of quantum coherent system. In this thesis, I'm using numeric method plus theoretical analysis to answer the questions: What are the low energy modes in disordered quantum spin system? How will environment dissipation damp the spin system's quasi-particle excitation quantitatively?

There are three parts in my thesis. Part 1 is the study of disordered quantum Ising chain. Part 2 is a numerical method for analytic continuation. Part 3 is the study of dissipative quantum Ising chain.

Wetland carbon sequestration is offset by carbon dioxide (CO2) and methane (CH4) emissions for which the magnitudes remain coarsely constrained. To better understand the spatial and temporal variations of gaseous carbon fluxes from marsh soils in a Mediterranean climate, I collected air and soil samples over the course of 10 months at Carpinteria Salt Marsh Reserve (CSMR) located in the County of Santa Barbara, California. The CSMR consists of four zones characterized by differences in elevation, tidal regime, soil properties, and vegetation. Twelve static chambers were deployed among two lower marsh zones, a mudflat, and a marsh-upland transition zone for fortnightly flux measurements from September 2015 to May 2016. In August 2015 and June 2016, soil cores up to 50 cm deep were extracted near the chambers, segmented by depth, and analyzed for soil moisture, bulk density, particle size distribution, electrical conductivity, pH, organic/inorganic carbon, and total nitrogen content. Averaged over the 9-month study period, the marsh-upland transition zone had the highest CO2 fluxes at 5.3 ± 0.7 g CO2 m-2 d-1, followed closely by the lower marsh zones (3.8 ± 0.6 g CO2 m-2 d-1 and 2.8 ± 0.7 g CO2 m-2 d-1), which were one order of magnitude higher than the CO2 fluxes from the mudflat (0.4 ± 0.1 g CO2 m-2 d-1). The CO2 fluxes varied significantly on a seasonal scale but were not consistently correlated with environmental variables measured. The CH4 fluxes had no clear seasonal patterns, but overall CH4 flux rates from the lower marsh zones (2.2 ± 1.5 mg CH4 m-2 d-1 and 1.9 ± 0.2 mg CH4 m-2 d-1) surpassed those from the mudflat (0.2 ± 0.06 mg CH4 m-2 d-1) by an order of magnitude, and the marsh-upland transition zone was a net methane sink (-0.07 ± 0.1 mg CH4 m-2 d-1). The CH4 fluxes correlated well with most soil properties by zone. Our results show that soil gaseous carbon fluxes from a coastal salt marsh vary by salt marsh zone.

Zeroth order pseudodifferential operators with Morse--Smale dynamical assumption have been used as a model for the dynamics of internal waves. The operators provide a novel mathematical explanation to the formation of attractors for two dimensional internal waves in a bounded aquarium. In addition, the spectral properties are somewhat surprisingly related to phenomena in quantum scattering.

In this thesis we introduce an analogue of the scattering matrix and describe its geometric structure. We also study the dynamics of resonances and answer a question posed by Colin de Verdi ere by proving the generic absence of embedded eigenvalues.

The definition of the scattering matrix, although based on analogues with Euclidean scattering, is more involved as we need to deal with the principal symbols of Lagrangian distributions. After being conjugated by certain natural unitary operators, our scattering matrix turns out to be a Fourier integral operator and its canonical relation is related to the bicharacteristics of the operator.

Resonances for 0th order pseudodifferential operators are defined as limits of eigenvalues for the operator with viscosity. We show that the convergences rate is linear for simple embedded eigenvalues of the operator. We also consider 0th order perturbations of 0th pseudodifferential operators. A series expansion of resonances for the perturbed operators near embedded eigenvalues for the original operator is proved. A special case of this expansion gives the Fermi golden rule. Using the formulae for the coefficients in the expansion, we prove the absence of embedded eigenvalues for generic perturbation.

As a by-product of the study of 0th order pseudodifferential operators, we state and prove the sharp radial estimates in Besov spaces, which generalize the corresponding estimates in Sobolev spaces.