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Essays in Product Creation and Substitution
No full textThis dissertation contains three essays studying product creation and substitution. The first two chapters focus on the firm and how market regulations affect firms' decisions to create new products. The last chapter focuses on consumers and their demand substitution across products. Products exist in more narrow product spaces, based on shared characteristics, which firms and consumers take into account in their supply and demand decisions.
Chapter 1 examines the effect of price regulations on new product creation in pharmaceuticals. Rising pharmaceutical prices across the world is an important policy concern, particularly in developing countries, where access to essential medicines and healthcare is already limited. As a result, many countries have implemented or proposed price control policies. However, price controls may introduce market distortions, such as shortages, misallocation, and reduced incentives for firms to innovate. In the case of partial price controls, firms may also introduce new unregulated products, thereby increasing price dispersion. In this chapter, I study the impact of a partial price control policy in India's pharmaceutical sector on new product creation by existing firms. Using comprehensive pharmaceutical wholesale sales data and an event study framework, I study whether firms with greater exposure to the policy--based on their initial sales and prices--launch new products in response to the policy announcement. I find that firms with greater policy exposure do not create new products or enter new markets post-policy. Particularly, they also do not create new products of unregulated formulations even within the regulated active ingredient markets. These findings suggest that the policy may have successfully reduced prices for consumers without distorting firms' incentives to create new products to cannibalize the sales of their existing regulated products.
Chapter 2, coauthored with Gianluca Antonecchia, Ajay Bhaskarabhatla, and Eric Verhoogen, studies the path of product evolution within pharmaceutical firms in India, with a focus on newly available markets due to patent expirations. When firms adopt new products and expand their product scope, they may invest in new technologies, increase product quality, and improve worker training. This process is known as firm upgrading and is particularly important for firm growth in developing countries. However, strong patent protections encourage innovation and R&D in developed countries while hindering firm upgrading in developing countries by restricting firm entry into new markets and technologies. We study how firms in India's pharmaceutical sector expand into new markets and technologies when drug markets become newly available after a patent expiration in the United States. We propose new measures of proximity between firms and drugs they have not yet adopted and distinguish between proximity in production technology (supply-side) and proximity in therapeutic use (demand-side). We show that in general firms are more likely to adopt drugs that are similar to those they already produce, especially if they are similar to their core product. Once a market newly opens due to a patent expiration, we observe firm entry into the newly available market, particularly by technologically distant firms. Our results suggest that patents hinder access to medicines and slow firm upgrading in developing countries by delaying firm entry into new and differentiated markets.
Chapter 3, coauthored with Colin Hottman, estimates the degree of demand substitution between goods produced in different countries. This parameter, known as the Armington elasticity, is an important measure in international trade and macroeconomics, as it determines the magnitude of the relative demand response to international relative prices. For example, the efficacy of trade policy tools--such as tariffs--in shifting demand toward domestically produced goods will depend on the substitutability of U.S. goods and imports. We are the first to combine U.S. retail scanner data with barcode-level country of origin information for a broad set of product categories. We use this novel data to estimate the degree of substitution between domestically produced goods and imports in U.S. retail. In doing so, we develop a novel generalization of Feenstra (1994) for nested demand systems, and apply this approach to a novel, non-homothetic generalization of nested CES preferences with rich substitution patterns. Unlike prior work, our results provide clear evidence that the macro elasticity of substitution (between U.S. and foreign goods) is significantly smaller than the micro elasticity of substitution (within domestic or foreign varieties) for nearly all product categories. We apply our model to three origins--domestic goods, imports from low-income countries, and imports from high-income countries--and find that within-origin substitution is still substantially larger than across-origin substitution. These results have important implications for trade policy, as they suggest that tariffs on Canada would lead to greater substitution toward imports from other high-income countries (such as Germany or France) than toward U.S. products, and tariffs on Mexico would lead to greater substitution toward imports from other low-income countries (such as China) than toward U.S. products
Exploring the Role of Cross-Cultural Professional Development on Educational Acculturation Strategies of Kazakhstani Mathematics Faculty
No full textThis study addresses the limited attention given to cultural factors when evaluating the influence of professional development (PD) programs rooted in one mathematics educational tradition on participants from another educational tradition.
The study examines the effect of a cross-cultural PD program led by a team of United States and Kazakhstani mathematics education experts on six Kazakhstani mathematics faculty perceptions and teaching practices. Data were collected through surveys, interviews, and lesson recordings.
Findings indicate that cross-cultural PD primarily influenced perceptions and teaching practices that required minimal effort, such as the integration of technology tools, while culturally rooted aspects, such as teaching approaches, were not affected. The study proposes a theoretical framework that provides guidance for future research on the effectiveness of cross-cultural PD as an acculturation process
Transforming Urban Public Transportation: Recommendations to Enhance Efficiency, Safety, and Cleanliness in New York City’s Subway System
No full textThe New York City subway system, operated by the Metropolitan Transportation Authority (MTA), is a critical component of urban mobility but faces persistent challenges related to delays, safety, and cleanliness. These issues undermine system reliability and negatively shape public perception. This thesis examines how targeted design interventions and technology-driven solutions can improve subway operations, enhance commuter safety, and create a cleaner transit environment.
Using a mixed-methods approach, the thesis analyzes publicly available transit performance data, commuter survey responses, and global case studies to evaluate best practices applicable to New York City. The findings inform a set of evidence-based recommendations for the MTA and policymakers that address operational inefficiencies and commuter concerns, with a particular focus on the potential for platform screen doors, predictive maintenance, and automated cleaning systems to improve service reliability and public trust in the subway system
Reinforcement Learning via Differentiable Simulation: Applications in Operations Management
No full textReinforcement learning (RL) is a promising approach for solving dynamic decision-making problems that arise in operations management applications, including scheduling, routing, supply chain management, and adaptive experimentation. However, so far RL algorithms suffer from high sample complexity and difficulty in scaling to large scale problems.
To address these issues, this dissertation proposes a model-based approach to RL via differentiable simulation. Differentiable simulation is a technique for computing gradients of a system’s dynamics with respect to any parameters or action inputs, which has been widely used in physics and robotics, with roots in the stochastic simulation literature dating back to the 1980s-1990s with methodologies such as infinitesimal perturbation analysis (IPA) and generalized likelihood ratio estimation.
In this thesis, we propose approximations which overcome non-differentiability in the action spaces and transition functions for two critical problem domains: adaptive experimentation and queuing network control. For adaptive experimentation, we discuss how the common practice of batched treatment allocation (i.e. allocating treatments to a batch of sampling units at a time) gives rise to principled statistical approximations that enable smoothed formulations of decision-making performance (e.g. regret) that can be directly optimized via stochastic gradient descent. For queuing network control, we introduce a novel smoothing technique for discrete-event systems that enables pathwise policy gradients for updating a reinforcement learning policy. Finally, we introduce a theoretical framework for studying the convergence of stochastic gradient descent for policy optimization that can be applied for a general class of gradient estimators
The Mind Medium: A Yin-Yang Philosophy of Mind and Media
No full textIn this dissertation, I articulate a philosophy of mind and media with the key concepts of the Yijing (Book of Changes) paradigm by examining their re-mediation in modern and contemporary Chinese media practices and connecting them to western philosophical debates on media, mind, time, and space. I focus on the notion of xin (the heart-mind), as its unthinkability within modern empiricism underlies not only the marginalization of the Yijing paradigm but also a series of theoretical conundrums we face in understanding the relationships between mind and body, concept and perception, message and media, and finally, theory and text.
I argue that the mind is inherently cosmic rather than just individual in the Yijing paradigm by showing how space-time cannot be perceptually given without the conceptual mediation of the mind that is fundamentally yin-yang patterned. Perception turns out to be profoundly divinatory, much more extraordinary than Yijing divination is ordinary. The cosmic mind is therefore the condition of possibility of media, accounting for the intelligibility of media as a meta-medium. Methodologically, this profoundly creative philosophy of the Yijing reveals text interpretation to be a divinatory art of co-creation with the cosmic mind.
On the one hand, each of the four chapters of this dissertation theorizes an intermedial dynamic in the work of a modern or contemporary Chinese writer, photographer, or filmmaker. Chapter 1 examines film and literature in considering Lu Xun’s conception of literature as what he calls, “the voice of the mind.” Chapter 2 engages Lang Jingshan’s application of the theories of traditional Chinese painting in the technological medium of photography and considers his work as photographic cosmology. Chapter 3 looks into the interplay of theatre and fiction film in Chen Kaige’s cinema and conceive them as cinematic metaphysics. Chapter 4 investigates how the intermedial play between music, digital image, documentary image, and mystical elements of martial arts in Jia Zhangke’s fiction films constitutes a cinematic reconciliation between epistemology and ethics.
On the other hand, each of the four chapters focuses on a key concept of the Yijing paradigm and examines how their re-mediation in modern and contemporary Chinese media practices resonates with pre-modern Chinese philosophers’ elaborations on them. Chapter 1 shows that xin (the hear-mind), manifesting in Lu Xun’s works as the first-person narrator, is a conceptual medium necessary for space-time and therefore the medium of all media in space-time. Examining Lang Jingshan’s manual for composing a yin-yang micro-cosmos within a photograph,
Chapter 2 demonstrates the materiality of media to be the vitality of qi (vital energy). Teasing out the yin-yang interplay of the real with the virtual in Chen Kaige’s films, Chapter 3 argues that the spatiality of the media involves the entanglement of the physical with the metaphysical. Articulating the five-phases theory of time in Jia Zhangke’s realist cinema, Chapter 4 shows how this realism is in fact celestial in a Yijing sense and the temporality of media is the yin-yang dynamic of the epistemologically real and the ethically good. Explaining the concepts of “pre-heaven,” (xian tian), “aligning and orienting” (jing-ying), “supra-formal” (xing er shang), “change-transformation” (bian-hua), and “cosmic resonance” (gan-ying) along the way, these four chapter together constitute a yin-yang philosophy of mind and media
Robust and Tractable Policies for Resource Allocation under Uncertainty.
No full textDecision-making under uncertainty is a central challenge in many resource planning and allocation problems including inventory planning, order fulfillment, supply chain management, revenue management, scheduling, and matching. Effectively addressing this challenge requires careful modeling of uncertainty based on available information and a tailored design of solution methods adapted to the specific recourse mechanisms involved. In this dissertation, we study fundamental resource allocation problems under uncertainty.
Chapters 1 and 2 focus on inventory planning and allocation under demand uncertainty. Specifically, in Chapter 1, we consider a multi-product setting where the decision-maker first sets initial inventory levels for each product. Then, after demand is realized, they are allowed to order more inventory, typically at a higher cost. The decision maker has access to an uncertainty set of possible customer demand scenarios and seeks to minimize costs in the face of the worst-case scenario of demand. This is modeled through a two-stage robust optimization problem for which we develop an LP-based approximation with provable guarantees that nearly match the hardness of the problem. Our approximation is also shown to be significantly faster than state-of-the-art solution methods. Our approximation leverages an interesting connection between the two-stage robust problem and disjoint bilinear programming and is closely related to the widely used affine policies.
In Chapter 2, we study a multi-location inventory problem where the decision maker first plans inventory allocation across multiple locations and subsequently decides how to fulfill sequentially realizing customer demand. The decision maker has only access to moment information about the cross-location customer demand and seeks to minimize costs under the worst-case demand distribution consistent with the moment information. We develop and analyze a policy that significantly extends the seminal solution of Scarf (1957) to the multi-location setting. Our solution methodology introduces a novel hierarchical clustering of metric spaces which may be of independent interest in robust and distributionally robust multi-location inventory management under uncertainty. We establish theoretical guarantees for our policy’s performance and demonstrate its empirical effectiveness through extensive numerical experiments.
In Chapter 3, we study the load balancing problem in an adversarial setting where jobs arrive and depart arbitrarily from a set of machines. Recourse actions (job reassignments) are allowed and the goal is to maintain a small maximum load using a small number of reassignments. This arises in many practical applications including task-machine assignments in data centers and bike-sharing systems. We propose a constant competitive algorithm with constant amortized recourse under bounded job degrees. This improves upon the previously known bounds for the problem which are logarithmic in the number of jobs.
In Chapter 4, we study the problem of assigning students to schools in which students and/or school seats often enter and leave the market after an initial stable matching is decided. The goal is to choose an initial stable matching that, in addition to being of high-quality, allows for adaptations with minimal changes after uncertainty is revealed. We study the problem in a two-stage stochastic framework and design a (pseudo)-polynomial algorithm
The N2-, O2-, and air-broadened halfwidths and line mixing parameters of the N2O molecule and their temperature dependences
No full textBroadening and line mixing parameters for N2-, O2-, and air-broadened N2O transitions in the v1 band are investigated over temperatures ranging of 195 to 350 K, using the Refined Robert Bonamy formalism. The theoretically predicted halfwidths show very good agreement with experimental data from the literature, leading to a reliable prediction of the rotational dependence of the temperature exponent N. Since our model yields the full relaxation matrix W, it also enables calculation of Rozenkranz line mixing parameters. Based on the reasonable agreement with available data at room temperature, the temperature dependence of the Rozenkranz parameters has been analyzed, and its physical origin is briefly discussed
Harnessing residents’ practice-based inquiries to enhance research literacy: The Thoughtful Reading of Evidence into Clinical practice (T-RECS) initiative.
No full textIntroduction: Research literacy is an important competency for all clinicians, but developing resident enthusiasm for it is difficult. At one academic emergency medicine (EM) residency program, we designed an innovative program to help residents improve literacy skills within a community of practice and use research literature to address clinical problems.
Methods: A six-member faculty core team surveyed residents to assess their baseline experience with evidence-based medicine (EBM) and level of engagement with the medical literature. Interested residents joined an iterative curriculum development process that drew on previous EBM pedagogical experience and literacy theory. We developed a semi-structured approach that prioritizes using the reference frame of clinical applicability rather than research methodology. We held 90-120 minute sessions three times a year as part of the regular residency didactic conference; post-session evaluations with quantitative and qualitative elements were used to adjust subsequent didactics to refine the approach.
Results: An average of 48 residents were in the EM training program during the nine sessions conducted during the study period. At baseline, residents had a high degree of exposure to EBM during medical school (94% of respondents) but low confidence in reading the medical literature (25%) or applying research to practice (10%). In contrast, they reported the novel program equipped them with skills to interpret literature and led to collective practice improvement. We found engagement was highest when residents led sessions based on inquiries that emerged out of their own training experience. Other positive factors included well-facilitated discussions between residents, relating questions to data-driven review of local practice patterns and addressing findings from free open access medical education (FOAMed) sources. The initial stages required significant team effort to design the pilot sessions, but later sessions were developed following the trajectory of resident inquiries using a minimally structured faculty consensus process and required less than 12 total faculty hours of commitment.
Conclusion: An innovative program centered on residents’ practice-based queries of research literature appears to enhance learner enthusiasm for development of research literacy. Further development is needed to validate the overall effectiveness and generalizability of this approach
Governance Development and Accessibility Readiness of Municipal Home Pages and Municipal Service Portals in the United States
No full textDespite how crucial municipal websites are to urban planning in omnichannel governance, there are shortcomings in effectively information dissemination, public participation, and successful service delivery in an attention economy despite rapid digitalization. Municipal websites may not be optimized to serve central roles in municipal service informational flows in a platform economy, leading to a further stratification of a gap between citizen needs and e-participation. Difficulties in service findability and usability for municipal residents might substantially affect at-risk urban populations.
With the time being 20 years past the E-Government Act of 2002, the study sought to examine the development and maturity of municipal websites and municipal service portals. With growing conversations in Congress and the legal system how the American Disability Act applies to websites, the study also sought to examine how municipal websites and municipal service portals are performing in digital accessibility. Municipal websites did not seem to be as developed and the lack of features such as sitemaps, search navigation tools on service portals, and lack of languages on some websites poses questions of website accessibility and maturity for populations such as people with low digital literacy or non-English speakers.
Despite high levels of ARIA features, municipal websites showed strong presences of accessibility alerts and errors, which poses problems for the differently abled who might physical or cognitive disabilities like the blind, the deaf, and those with low vision. Planners should advocate for digital e-inclusion, helping to create more inclusive digital governance, smart city, and platform urbanism models
Comparative Study of Informal Economies in Marginalized Communities: Xiaobei, Guangzhou, and Harlem, New York
No full textThis thesis examines informal economic practices among West African migrants in Xiaobei and Harlem. Using interviews and field observations, it explores how these communities adapt to exclusion through trade networks. The study argues that formalizing informal economies can promote inclusive, equitable urban development