False Discovery Rate Controlled Heterogeneous Treatment Effect Detection for Online Controlled Experiments

Online controlled experiments (a.k.a. A/B testing) have been used as the mantra for data-driven decision making on feature changing and product shipping in many Internet companies. However, it is still a great challenge to systematically measure how every code or feature change impacts millions of users with great heterogeneity (e.g. countries, ages, devices). The most commonly used A/B testing framework in many companies is based on Average Treatment Effect (ATE), which cannot detect the heterogeneity of treatment effect on users with different characteristics. In this paper, we propose statistical methods that can systematically and accurately identify Heterogeneous Treatment Effect (HTE) of any user cohort of interest (e.g. mobile device type, country), and determine which factors (e.g. age, gender) of users contribute to the heterogeneity of the treatment effect in an A/B test. By applying these methods on both simulation data and real-world experimentation data, we show how they work robustly with controlled low False Discover Rate (FDR), and at the same time, provides us with useful insights about the heterogeneity of identified user groups. We have deployed a toolkit based on these methods, and have used it to measure the Heterogeneous Treatment Effect of many A/B tests at Snap

An exploration of composite language modeling for speech recognition

Title from PDF of title page (University of Missouri--Columbia, viewed on September 12, 2013).The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Thesis advisor: Dr. Yunxin ZhaoIncludes bibliographical references.M.S. University of Missouri--Columbia 2013.Dissertations, Academic -- University of Missouri--Columbia -- Computer science."May 2013"Language models are one of the most critical knowledge sources of automatic speech recognition (ASR) systems. In the past decades, many language models have been developed, and some have proved useful and successful in speech recognition systems. However, almost all language models only capture one or two aspects of natural language. This study aims to investigate the effects of a syntactic, semantic, and lexical language model on speech recognition. In this study, we refer this language model as the composite language model (CLM). The parameters of the CLM in our study are distributed among hundreds of computer nodes in a supercomputer because they are too large to be stored in just one computer node. A distributed application has been developed to implement two speech rescoring techniques by using the CLM: lattice rescoring and confusion network rescoring. Experiments on a Wall Street Journal task have shown that using CLM to rescore word lattices and confusion networks have led to improvements in word accuracy over the commonly used trigram language model, with the latter offering a larger performance gain

Semi-Empirical Method for Estimating Stiffness and Deformation of Cylindrical Retaining Diaphragm Wall

This study presents a semi-empirical method to estimate stiffness and deformation of cylindrical retaining diaphragm wall. Based on the concept of "arch-beam" method, the retaining structure is separated into two structural components: arch unit and supported beam unit. The stiffness of both units is computed by parameter analytical method and then combined to obtain the total retaining stiffness of cylindrical diaphragm wall. The proposed model incorporates major factors considered in design of cylindrical retaining structure such as soil condition, geometry of excavation, geometries and materials of diaphragm wall, spacing and stiffness of ring beam, joints in diaphragm wall. A statistical equation is developed to relate the stiffness and lateral wall deformation. The proposed stiffness and deformation model is validated by 24 cylindrical excavation cases in literature

Digital piracy, creative productivity, and customer care effort: evidence from the digital publishing industry

We empirically investigate how writers’ output is affected by copyright piracy using data from a Chinese digital publishing platform. We identify two measurements of writers’ output—creative productivity and customer care—which are also affected by readers’ feedback through purchasing, tipping, and commenting. We take advantage of an exogenous event—the termination of a free personal storage service and search function by a leading Chinese cloud storage provider in June 2016—to causally identify the effects of the resulting reduced copyright piracy on writers’ efforts. Using a difference-in-differences modeling approach, we compare the changes in average writer behavior before and after the event across two groups of writers: (1) writers who have profit-sharing contracts with the platform and (2) those who do not. We find that after the termination, contracted writers increased their creative productivity efforts in terms of quantity without sac-rificing quality but reduced their customer care efforts. However, these effects are absent for noncontracted writers. Our study is among the first to provide empirical support for the positive effect of digital intellectual property rights infringement re-duction on creative productivity

Imperfect Preventive Maintenance Policies With Unpunctual Execution.

Traditional maintenance planning problems usually presume that preventive maintenance (PM) policies will be executed exactly as planned. In reality, however, maintainers often deviate from the intended PM policy, resulting in unpunctual PM executions that may reduce maintenance effectiveness. This article studies two imperfect PM policies with unpunctual executions for infinite and finite planning horizons, respectively. Under the former policy, imperfect PM actions are periodically performed and the system is preventively replaced at the last PM instant. The objective is to determine the optimal number of PM actions and associated PM interval so as to minimize the long-run average cost rate. While the latter policy specifies that a system is subject to periodic PM activities within a finite planning horizon and there is no PM activity at the end of the horizon. The aim is then to identify the optimal number of PM activities to minimize the expected total maintenance cost. We discuss the modeling and optimization of the two unpunctual PM policies, and then explore the impact of unpunctual executions on the optimal PM decisions and corresponding maintenance expenses in an analytical or numerical way. The resulting insights are helpful for practitioners to adjust their PM plans when unpunctual executions are anticipated

Optical Study of Liquid Crystal Lens Doped with Multiwalled Carbon Nanotubes

In this paper, a new kind of electrically controlled liquid crystal lens, which respond in a relatively fast time, is presented. The multiwalled carbon nanotubes are doped into liquid crystal to fabricate the liquid crystal lens. As 0.02 % concentration of multiwalled carbon nanotubes is uniformly distributed in the liquid crystal, the optical features of the liquid crystal lens are obviously improved. The liquid crystal lens with a diameter of 2.0 mm was fabricated with about 0.2 s response time and less than 5 Vrms applied voltage. The focal length can vary from 16 to 510 mm, and the operation voltage changes from 1.0 to 5.5 Vrms. This liquid crystal lens has the very attractive feature of submillisecond response time, which is a much faster response time in comparison with conventional liquid crystal lens. Thus, this kind of liquid crystal lens has high potential for implementation in many practical imaging applications and imaging commercialisation

Fast-Response Liquid Crystal Lens Doped with Multi-Walled Carbon Nanotubes

In this paper, a relatively fast-response liquid crystal (LC) lens was proposed, which was fabricated by a simple method. Multi-walled carbon nanotubes (MWCNTs) were utilized in fabricating the LC lens. As MWCNTs were doped into the LCs, the dielectric anisotropy of the mixture changed, which was the key factor in solving the technical barrier of slow response time. In experiments, the effects of doping with MWCNTs were demonstrated. The concentration of doped MWCNTs was discussed in detail, and the best concentration and doping method were analyzed. The relationship between the concentration and response time was also obtained. This LC lens had a sub-millisecond response time, which was a relatively fast response time in comparison to conventional LC lenses of pristine LCs. Thus, this proposed method could be considered as a new method to realize fast-response LC lens

Chinese Family Strengths and Resiliency

Chinese family and marriage strengths and challenges are delineated in this article, including equity in marriage, affection, the ability to adapt to changes, mutual trust, compatibility, harmony, and family support. Despite the fact that Chinese households are getting smaller as a result of governmental policy and the broadening of housing markets, families remain crucial support networks, especially in the areas of socialization and intergenerational relationships. Current research on Chinese marriages and families is cited, outlining attitudinal changes regarding mate selection, divorce, and childbirth between genders, between older and younger generations, and between urban and rural residents

Azorhizobium caulinodans c-di-GMP phosphodiesterase Chp1 involved in motility, EPS production, and nodulation of the host plant

Establishment of the rhizobia-legume symbiosis is usually accompanied by hydrogen peroxide (H2O2) production by the legume host at the site of infection, a process detrimental to rhizobia. In Azorhizobium caulinodans ORS571, deletion of chp1, a gene encoding c-di-GMP phosphodiesterase, led to increased resistance against H2O2 and to elevated nodulation efficiency on its legume host Sesbania rostrata. Three domains were identified in the Chp1: a PAS domain, a degenerate GGDEF domain, and an EAL domain. An in vitro enzymatic activity assay showed that the degenerate GGDEF domain of Chp1 did not have diguanylate cyclase activity. The phosphodiesterase activity of Chp1 was attributed to its EAL domain which could hydrolyse c-di-GMP into pGpG. The PAS domain functioned as a regulatory domain by sensing oxygen. Deletion of Chp1 resulted in increased intracellular c-di-GMP level, decreased motility, increased aggregation, and increased EPS (extracellular polysaccharide) production. H2O2-sensitivity assay showed that increased EPS production could provide ORS571 with resistance against H2O2. Thus, the elevated nodulation efficiency of the increment chp1 mutant could be correlated with a protective role of EPS in the nodulation process. These data suggest that c-di-GMP may modulate the A. caulinodans-S. rostrata nodulation process by regulating the production of EPS which could protect rhizobia against H2O2