Moment Inequalities in the Context of Simulated and Predicted Variables

This paper explores the effects of simulated moments on the performance of inference methods based on moment inequalities. Commonly used confidence sets for parameters are level sets of criterion functions whose boundary points may depend on sample moments in an irregular manner. Due to this feature, simulation errors can affect the performance of inference in non-standard ways. In particular, a (first-order) bias due to the simulation errors may remain in the estimated boundary of the confidence set. We demonstrate, through Monte Carlo experiments, that simulation errors can significantly reduce the coverage probabilities of confidence sets in small samples. The size distortion is particularly severe when the number of inequality restrictions is large. These results highlight the danger of ignoring the sampling variations due to the simulation errors in moment inequality models. Similar issues arise when using predicted variables in moment inequalities models. We propose a method for properly correcting for these variations based on regularizing the intersection of moments in parameter space, and we show that our proposed method performs well theoretically and in practice

Embracing traditional Chinese culture through design

As a designer from China I am constantly focused on my passion for design of China, This interest comes from both my commitment to deep-rooted Chinese traditions, and my concern with regards to the gradual loss of traditional cultural values within contemporary society. As a product designer, I really like designing daily object, through exploring the relationship between consciousness and behavior. I consider this connection in order to make objects more meaningful to users. This project discusses the current situations of Chinese traditions and cultural values, and the challenges they face to survive in the contemporary world. My mission is to arouse the resonance to traditional cultural values with modern Chinese and inspire them to carry out those values in details of everyday life

Essays on dynamic demand, pricing and investment

My dissertation develops and applies empirical structural models to study consumers’ dynamic adoption of durable goods, and firms’ dynamic research and development (R&D) investment and pricing strategies. In Chapter 2, I study consumer purchase dynamics for a new technology good, the digital single-lens-reflex (DSLR) camera, where consumer learning and switching costs across brands are present. Using a unique dataset that tracks individual DSLR camera ownership history, I find that low-end DSLR cameras are gateway products that most consumers buy initially. When some consumers choose to repurchase, they are more likely to buy high-end DSLR cameras from the same brand as the initial purchases. Combining individual camera ownership data with aggregate sales data, I develop and estimate a dynamic demand model that incorporates consumer learning and switching costs. The estimated demand model implies a dynamic complementary relationship between high- and low-end products that are produced by the same firm. In Chapter 3, I further empirically investigate the influence of consumer purchase dynamics on forward-looking firms’ pricing strategies. Supply-side simulations imply that firms have incentives to invest in their customer bases using low-end products and to harvest the resolved uncertainty of valuation and switching costs using high-end products. In Chapter 4, I explore the nature of uncertainty in innovation production through firms’ R&D investment. Utilizing a rich dataset that tracks Spanish manufacture firms’ R&D activities and innovation outcomes for up to 17 years, I build and estimate a dynamic model of firms’ R&D investment incorporates the uncertainties in innovation

Influence of Social Network Integration on the Online Review Helpfulness

Online consumer reviews are important for consumers when they make purchasing decisions. However, the large volume of online reviews makes it difficult for consumers to identify those helpful reviews. The influencing factors on online review helpfulness have drawn great attention from different research fields. In recent years, online review websites start to exhibit more features of social media. For example, some websites allow users to integrate with other social media accounts. The influences of such social factors, however, are rarely studied in the literature. Drawing on a dataset from Qunar.com, this paper explores how social network integration and reviewer network centrality influence online review helpfulness through a negative binomial regression model. Our results show that both factors have a positive effect on review helpfulness, and that network centrality positively moderates the effect of social network integration. Our research results provide important implications for reviewers, industry practitioners, and online review websites

Effects of Cations and PH on Antimicrobial Activity of Thanatin and s-Thanatin against _Escherichia coli_ ATCC25922 and _B. subtilis_ ATCC 21332

Thanatin and s-thanatin were insect antimicrobial peptides which have shown potent antimicrobial activities on a variety of microbes. In order to investigate the effect of cations and pH on the activity of these peptides against Gram-negative bacteria and Gram-positive bacteria, the antimicrobial activities of both peptides were studied in increasing concentrations of monovalent cations (K^+^ and Na^+^), divalent cations (Ca^2+^ and Mg^2+^) and H^+^. The NCCLS broth microdilution method showed that both peptides were sensitive to the presence of cations. The divalent cations showed more antagonized effect on the activity against Gram-negative bacteria than the monovalent cations, since the two peptides lost the ability to inhibit bacterial growth at a very low concentration. In addition, the activities of both peptides tested were not significantly affected by pH. Comparing to studies of other antibacterial peptide activities, our data support a hypothesis that positive ions affect the sensitivity to cation peptides