Semiparametric Estimation of Partially Varying-Coefficient Dynamic Panel Data Models

This paper studies a new class of semiparametric dynamic panel data models, in which some of the coefficients are allowed to depend on other informative variables and some of the regressors can be endogenous. To estimate both parametric and nonparametric coefficients, a three-stage estimation method is proposed. A nonparametric GMM is adopted to estimate all coefficients firstly and an average method is used to obtain the root-N consistent estimator of parametric coefficients. At the last stage, the estimator of varying coefficients is obtained by plugging the parametric estimator into the model. The consistency and asymptotic normality of both estimators are derived. Monte Carlo simulations verify the theoretical results and demonstrate that our estimators work well even in a finite sample.This paper is accepted by Econometric Reviews

A New Forecasting Model for USD/CNY Exchange Rate

This paper models the return series of USD/CNY exchange rate by considering the conditional mean and conditional volatility simultaneously. An index type functional-coefficient model is adopted to model the conditional mean part and a GARCH type model with a policy dummy variable is applied to the conditional volatility model. We show that the government policy indeed has an impact on the exchange rate dynamic. To evaluate the out-of-sample forecasting ability, a prediction interval is computed by employing nonparametric conditional quantile regression. Our method outperforms other popular models in terms of various criteria

Semiparametric Estimation of Partially Varying-Coefficient

This paper studies a new class of semiparametric dynamic panel data models, in which some coefficients are allowed to depend on some informative variables and some regressors can be endogenous. To estimate both parametric and nonparametric coefficients, a three-stage semiparametric estimation method is proposed. The nonparametric GMM is proposed to estimate all coefficients firstly and the average method is used to obtain the root-N consistent estimator of parametric coefficients. At the last stage, the estimator of varying coefficients is obtained by plugging the parametric estimator into the model. The consistency and asymptotic normality of both estimators are derived, and furthermore, the efficient estimation of parametric coefficients is discussed. Monte Carlo simulations verify the theoretical results and demonstrate that our estimators work well even in a finite sample.

Innovative use of industrially produced steel slag powders in asphalt mixture to replace mineral fillers

Using steel slag to partially replace the natural aggregate in asphalt mixture to produce high-performance asphalt mixture has gained significant interest in recent years as a value-added option to recycle steel slag. However, the poor homogeneity of the material properties of steel slag aggregates remains a concern for this recycling approach. In this study, an innovative method of using industrially produced steel slag powder (SSP) to replace the mineral filler in asphalt mixture was proposed to address this concern. Five fillers, including four SSP fillers, obtained by grinding different steel slag aggregates with an industrialized production line, and one conventional limestone powder (LP) filler, were evaluated. The chemical compositions and micro-morphologies of the SSPs were first characterized to evaluate the material homogeneity and gain insights into the advantages of using SSPs as fillers. Then, asphalt mixtures with different fillers were designed and produced, and their moisture stability, rutting resistance, and low-temperature crack resistance, were characterized. It was found that the industrially produced SSPs possessed homogeneous properties, and improved the compatibility between filler particles and asphalt binder. Besides, the asphalt mixtures with SSP fillers showed better resistance to the moisture damage, permanent deformation, low-temperature crack in terms of fracture energy, than the asphalt mixture with LP filler. Therefore, it was concluded that using SSPs as a replacement of mineral fillers in asphalt mixture provided a reliable and value-added solution to recycle steel slag

Utilization of Construction Waste Recycled Powder as Filler in Asphalt Concrete

Processing construction waste into aggregate and reusing it in asphalt pavement is beneficial in terms of environmental protection and resource utilization. However, recycled aggregate (RA) possesses some property defects. Therefore, RA usually needs to be strengthened by modification technologies prior to use. In order to promote the convenient and low-cost utilization of construction waste, a new method of preparing construction waste into powder and using recycled powder (RP) as asphalt filler is proposed in this research. The property defects of RA and the applicability of RP used as filler were first analyzed based on their material characteristics. Then, asphalt concrete with RP was designed according to the Superpave method, and the engineering performance of the asphalt mixture was further investigated. According to the results, we recommend the use of acidic RP in combination with other highly alkaline fillers, such as Portland cement (PC), with a suitable blending ratio of RP to PC of 1:1. Preparing asphalt concrete with filler composed of RP and PC can achieve satisfactory engineering performance

The Utilization of Graphene Oxide in Traditional Construction Materials: Asphalt

In the advanced research fields of solar cell and energy storing materials, graphene and graphene oxide (GO) are two of the most promising materials due to their high specific surface area, and excellent electrical and physical properties. However, they was seldom studied in the traditional materials because of their high cost. Nowadays, graphene and GO are much cheaper than before with the development of production technologies, which provides the possibility of using these extraordinary materials in the traditional construction industry. In this paper, GO was selected as a nano-material to modify two different asphalts. Then a thin film oven test and a pressure aging vessel test were applied to simulate the aging of GO-modified asphalts. After thermal aging, basic physical properties (softening point and penetration) were tested for the samples which were introduced at different mass ratios of GO (1% and 3%) to asphalt. In addition, rheological properties were tested to investigate how GO could influence the asphalts by dynamic shearing rheometer tests. Finally, some interesting findings and potential utilization (warm mixing and flame retardants) of GO in asphalt pavement construction were explained

Genomic and Proteomic Analysis of <i>Pseudomonas aeruginosa</i> Isolated from Industrial Wastewater to Assess Its Resistance to Antibiotics

Industrial wastewater usually contains a large amount of organic and inorganic pollutants, and many microorganisms. However, the types of microorganism present in industrial wastewater are still unclear. The aim of this study was to analyze the physicochemical properties and drug resistance of Pseudomonas aeruginosa isolated from industrial wastewater containing high concentrations of sulfate compounds. Pseudomonas aeruginosa was isolated from industrial wastewater from industrial produce with high concentrations of sulfate and phosphate, and mass spectrometry identification, gene identification, biochemical analysis and genomic and proteomic property identification were carried out. According to the results of matrix-assisted flight mass spectrometry and 16S rDNA sequencing, the isolated bacterium was identified as Pseudomonas aeruginosa, and was positive for reactions of ONPG, ACE, GLU, MNE, etc. Through growth experiments, it can be seen that Pseudomonas aeruginosa had a significant growth rate in the LB medium. Antibiotic sensitivity tests showed that Pseudomonas aeruginosa was susceptible to most antibiotics and moderately resistant to Polymyxin B and Polymyxin E. The drug resistance gene experiment showed that Pseudomonas aeruginosa had the gyrB gene related to antibiotic resistance. Proteomic analysis revealed that six proteins were involved in antibiotic resistance. This experiment isolated Pseudomonas aeruginosa from industrial produce wastewater containing high concentrations of sulfate and phosphate ions, providing a new perspective for further research on the characteristics and drug resistance of microorganisms in industrial wastewater and their potential functions when using them to deal with environmental pollution

Global Bibliometric Developments on Solid Waste Recycling in Concrete Construction Engineering

The precise and visual analysis of solid waste recycling in concrete construction engineering is critical for the development of ecological civilization and for the secure supply of resources. This research makes a bibliometric analysis of the solid waste application in concrete construction engineering from 2000 to 2021 based on the Web of Science. The global bibliometric status, current research focus and future directions were used to indicate the global development of solid waste recycling in concrete construction engineering. The most reused solid wastes and most solid waste productive regions were concluded with this bibliometric analysis. China is far ahead of other countries in solid waste recycling in all aspects and heavy metal is one of the most prominent solid waste themes in China. By analyzing the most studied solid waste, fly ash appears to be the most popular and is widely used; half of the top ten-cited papers are correlated with it