Productivity decomposition, price imputation and firm dynamics

The productivity slowdown across industrialised countries since 2004 is a persistent puzzle. This thesis proposes new productivity decompositions, using both industry and firm-level administrative data sets, with a focus on innovative techniques to advance understanding of the drivers of firm, industry, and country productivity performance. Particular attention is paid to micro-theoretic foundations of the proposed techniques, and to the rigorous application of appropriate econometric and data science techniques. At the industry level, drivers of productivity change are identified from a micro-theoretic framework implemented using an index number approach. Drawing on a non-parametric model, Chapter 2 decomposes productivity growth into explanatory factors for 12 selected industries and 16 market sector industries in Australia. Technical progress is found to support increasing productivity, though its contribution is partly offset by production inefficiency. Production inefficiency is interpreted as lagged output, inactive operation or possible measurement errors on a case-by-case basis. The overall performance of productivity growth and its explanatory factors is affected by the market shares based on a weighted average industry aggregation. In addition to the industry-level productivity decomposition in Chapter 2, a firm-level productivity decomposition is developed in Chapter 3 for a market that consists of incumbents, entrants and exiters. This new method enables decompositions of productivity into components to be merged with firm dynamics. The framework is applied to Australian firm-level data and reveals the dominant contribution of incumbent firms to industry productivity and industry efficiency. A difference-in-differences approach is proposed that validates the firm dynamics from the counterfactual perspective. Price imputation is essential when detailed price information is unavailable to support productivity decompositions. Chapter 4 introduces tree-based machine learning models for estimating missing prices in cases where there is product entry and exit, or product “churn”. Model performance metrics from (electronic-point-of-sale) scanner data confirm the prediction accuracy of tree-based models. An economic explanation is proposed to link the decision tree structure and consumer preferences. Tree-based models are recommended for price imputation due to their prediction accuracy and compatibility with consumer utility types

Production of Highly Monodisperse Polystyrene by Evaporative Purification

In this thesis, I will demonstrate a simple evaporative purification method to separate a polydisperse polystyrene with small molecular weight into highly monodisperse components (N-mers) ranging from 3-mers to 13-mers. This method has been applied to polystyrene samples of Mw= 600 g/mol and Mw= 890 g/mol with narrow molecular weight distribution, as well as a polystyrene sample of Mw=1200 g/mol with broader molecular weight distribution. In each case, the samples were successfully separated into milligram (mg) quantities of N-mers with N ranging from 3 to 13. The vapor pressure of each N-mer is calculated by using a simple lattice model and calculations suggest the isolated components have Mw/Mn values less than 1.001 and, through a second iteration of the process, Mw/Mn could become as low as 1.000003. The glass transition temperature (Tg) of each separated component is characterized by the differential scanning calorimeter and the Tg values of these components are independent of the sample they originate from. Based on the Tg values of these pure components, the Fox equation for the Tg of mixtures is developed into a simple relation which is able to accurately quantify the Tg values from oligomer to polymer

Stabilization and Controller Design of 2D Discrete Switched Systems with State Delays under Asynchronous Switching

This paper is concerned with the problem of robust stabilization for a class of uncertain two-dimensional (2D) discrete switched systems with state delays under asynchronous switching. The asynchronous switching here means that the switching instants of the controller experience delays with respect to those of the system. The parameter uncertainties are assumed to be norm-bounded. A state feedback controller is proposed to guarantee the exponential stability. The dwell time approach is utilized for the stability analysis and controller design. A numerical example is given to illustrate the effectiveness of the proposed method

An Optimization Approach for the Coordinated Low-Carbon Design of Product Family and Remanufactured Products

[EN] With increasingly stringent environmental regulations on emission standards, enterprises and investigators are looking for effective ways to decrease GHG emission from products. As an important method for reducing GHG emission of products, low-carbon product family design has attracted more and more attention. Existing research, related to low-carbon product family design, did not take into account remanufactured products. Nowadays, it is popular to launch remanufactured products for environmental benefit and meeting customer needs. On the one hand, the design of remanufactured products is influenced by product family design. On the other hand, the launch of remanufactured products may cannibalize the sale of new products. Thus, the design of remanufactured products should be considered together with the product family design for obtaining the maximum profit and reducing the GHG emission as soon as possible. The purpose of this paper is to present an optimization model to concurrently determine product family design, remanufactured products planning and remanufacturing parameters selection with consideration of the customer preference, the total profit of a company and the total GHG emission from production. A genetic algorithm is applied to solve the optimization problem. The proposed method can help decision-makers to simultaneously determine the design of a product family and remanufactured products with a better trade-off between profit and environmental impact. Finally, a case study is performed to demonstrate the effectiveness of the presented approach.This research was funded by National Natural Science Foundation of China (grant number 51575264 and 51805253); the Fundamental Research Funds for the Central Universities (grant number NP2017105); Jiangsu Planned Projects for Postdoctoral Research Funds (grant number 2018K017C); and the Qin Lan Project.Wang, Q.; Tang, D.; Li, S.; Yang, J.; Salido, MA.; Giret Boggino, AS.; Zhu, H. (2019). An Optimization Approach for the Coordinated Low-Carbon Design of Product Family and Remanufactured Products. Sustainability. 11(2):1-22. https://doi.org/10.3390/su11020460S122112Mascle, C., & Zhao, H. P. (2008). Integrating environmental consciousness in product/process development based on life-cycle thinking. International Journal of Production Economics, 112(1), 5-17. doi:10.1016/j.ijpe.2006.08.016Kengpol, A., & Boonkanit, P. (2011). 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Pyrolysis characteristics of waste tire particles in fixed-bed reactor with internals

This study investigated the characteristics of pyrolysis for waste tire particles in the newly developed fixed-bed reactor with internals that are a central gas collection channel mounted inside reactor. And a few metallic plates vertically welded on the internal wall of the reactors and extending to the region closing their central gas collection pipe walls. Experiments were conducted in two laboratory fixed bed reactors with or without the internals. The results shown that employing internals produced more light oil at externally heating temperatures above 700 °C due to the inhibited secondary reactions in the reactor. The oil from the reactor with internals contained more aliphatic hydrocarbons and fewer aromatic hydrocarbons, leading to its higher H/C atomic ratios as for crude petroleum oil. The char yield was relatively stable for two beds and showed the higher heating values (HHVs) of about 23 MJ/kg. The gaseous product of pyrolysis mainly consisted of H2 and CH4, but the use of internals led to less pyrolysis gas through its promotion of oil production. Keywords: Pyrolysis, Waste tire, Fixed bed, Internals, Secondary reaction