More is Less? Design Free Sample Strategy via Field Experiment and Double/Debiased Machine Learning

Free sample strategy has attracted considerable interest among practitioners and academics, it has been widely adopted in digital content industries (e.g., e-books, music, and videos). There are two issues that have been the continuous concerning and constantly optimized focus. How many free samples should be taken? How to design a personalized free samples strategy considering the contexts? To better understand these issues, we collaborated with an online reading platform in China to design and conduct a field experiment based on Construal Level Theory. The results showed an inverted U-shaped relationship between free sample quantity and consumer purchase decisions and also suggested when free chapters were offered, book popularity and quality were also found to positively moderate consumers’ purchase decisions. Moreover, by combining the causal forest (CF) technique and the double/debiased machine learning model (DML), we develop a personalized free sample strategy and provide managerial implications

Diagnose Pathogens in Drinking Water via Magnetic Surface-Enhanced Raman Scattering (SERS) Assay

Rapid identification and diagnosis of bacteria and other microorganisms is a great challenge for drinking water safety due to the increasing frequency of pathogenic infections. Raman spectroscopy is a non-destructive tool to characterize the biochemical fingerprints of bacterial cells and its signal can be improved by surface-enhanced Raman scattering (SERS). Thus, Raman scattering has a huge potential in fast diagnosis of pathogens in drinking water, with low cost and high reproducibility. In this work, we developed a novel fast diagnosis method to detect aquatic pathogens via magnetic SERS assay. With chemical coprecipitation synthesis and surface glucose reduction, the silver-coated magnetic nanoparticles (Ag@MNPs) had a welldeveloped core-shell structure and high efficiency to capture bacterial cells. Ag@MNPs achieved 103 enhancement factor for rhodamine 6G and the limit of detection was 10-9 M. The magnetic SERS assay also successfully detected various bacteria (A. baylyi and E. coli) with high sensitivity (105 CFU/mL). This platform provided a promising and easy-operation approach for pathogen detection for food and drinking water safety

Biospectroscopy diagnosis of bacterial interaction with environmental molecules

Aims: Bacteria are universal micro-organisms that can be found in almost all aquatic and terrestrial environments and strongly affect ecological systems at different spatial scales. The activities of bacteria are profound on the physicochemical features of natural environments, while natural environments shape bacterial behaviours through physical and chemical alterations. Different molecules present in the environment produce significant effects on bacteria. Therefore, it is required to study the rich and complementary interactions between bacteria and molecules. In this thesis, four research studies were conducted to investigate the interactions between bacteria and nanoparticles or carbonaceous substrates, deploying state-of-the-art techniques which can yield new insights. Methods: Raman micro-spectroscopy was employed in this thesis as a diagnostic tool to detect the biochemical alterations of bacteria post-exposure to different chemical molecules. Unlike conventional methods, such as light/electron microscopy, molecular analysis techniques and bacterial behaviour assays, Raman spectroscopy provides detailed information of biological constituents of bacteria that interact with diverse molecules. In addition, computational analysis including principal component analysis and linear discriminant analysis (PCA and LDA) was used to process the Raman spectral data. Results and Discussion: Raman spectra characterize the interaction between bacteria with different molecules. Spectral characterization showed the specific binding of nanoparticles with nucleic acids and amino acids in bacteria, and the different chemotactic behaviours of bacteria towards carbohydrates, organic acids and alkanes. Distinct spectral alterations allowed the evaluation of the alkane affinity in bacteria, and enabled quantification of the concentrations of glucose or organic acids in the aquatic phase. Furthermore, computational analysis of spectral alterations illustrated the effects of nutrient cations on alkane affinity in bacteria, and indicated the selective affinity of bacteria towards different organic carbonaceous molecules in the mixture of carbonaceous substances. Findings from this thesis showed that Raman spectroscopy is a rapid, reliable and non-destructive approach to investigate the interaction of bacterial cells with diverse molecules, which implies techniques involved in Raman spectroscopy can diagnose subcellular changes both in situ and in vivo post-exposure to different natural conditions or chemical molecules

Preparing and characterizing Fe3O4@cellulose nanocomposites for effective isolation of cellulose-decomposing microorganisms

This study developed Fe3O4@cellulose nanocomposites by co-precipitation synthesis for bacteria capture and isolation. By surface modification with cellulose, the Fe3O4@cellulose nanocomposites have 20 nm average particle size and 3.3–24.9 emu/g saturation magnetization. Living bacteria could be captured by the Fe3O4@cellulose nanocomposites and harvested by magnetic field, with high efficiency (95.1%) and stability (>99.99%). By metabolizing cellulose and destroying the Fe3O4@cellulose@bacteria complex, cellulose-decomposing microorganisms lost the magnetism. They were therefore able to be isolated from the inert microbial community and the separation efficiency achieved over 99.2%. This research opened a door to cultivate the uncultivable cellulose-decomposing microorganisms in situ and further characterize their ecological functions in natural environment

A modulated model predictive control scheme for the brushless doubly-fed induction machine

This paper proposes a modulated model predictive control (MMPC) algorithm for a brushless double-fed induction machine. The Brushless Doubly-Fed Induction Machine has some important advantages over alternative solutions for brushless machine applications. The proposed modulation technique achieves a fixed switching frequency, which gives good system performance. The paper examines the design and implementation of the modulation technique and simulation results verify the operation of the proposed modulation technique

Magnet bioreporter device for ecological toxicity assessment on heavy metal contamination of coal cinder sites

A novel magnet bioreporter device was developed in this research for soil toxicity assessment, via magnetic nanoparticles functionalized whole-cell bioreporters. The whole-cell bioreporter ADPWH-recA kept response capability to DNA damage after magnetic nanoparticles (MNPs) functionalization, and could be harvested from soil samples by permanent magnet to reduce the soil particle disturbance. Compared to conventional treatments applying bioreporter directly in soil-water mixture (SW-M treatment) or supernatant (SW-S treatment), MNPs functionalized bioreporter via the magnet device (MFB) treatment achieved high sensitivity to evaluate the toxicity and bioavailability of chromium contamination in soils from 10 mg/kg to 5000 mg/kg soil dry weight. The MNPs functionalized bioreporter also achieved high reproducibility with pH value from 5.0 to 9.0, salinity from 0% to 3% and temperature from 20 °C to 37 °C. A case study was carried out on the ecological toxicity assessment of heavy metal contamination at the coal cinder site via the magnet bioreporter device. The heavy metal toxicity declined with the increasing distance to the coal cinder point, and a significant accumulation of heavy metal toxicity was observed along the vertical distribution. No direct link was found between the pollution load index (PLI) and heavy metal toxicity, and the results suggested the bioreporter test monitored the toxicity of heavy metals in soils and was an important approach for ecological risk assessment. Magnet bioreporter device also offered the high throughput biological measurement and was feasible for in situ monitoring

Realisation of responsive and sustainable reconfigurable manufacturing systems

There is a lack of a design method for the manufacturing system reconfiguration to cope with the changing demand and evolving production technologies while minimising energy consumption. The key drivers for the new industrial paradigm are flexibility and sustainable manufacturing, which have been studied independently in the prior research. The aim of this research is to study two drivers simultaneously by designing robust models and analysing manufacturing system configurations to achieve feasible solutions in any scenario that may arise due to evolving, incomplete, and unforeseen production requirements, while minimising energy usage during product manufacture. To achieve this goal, this research develops a robustly validated pre-emptive decision engineering framework (DEF) for the manufacturing system reconfiguration process to manage future uncertainty of future conditions and identifies current production vulnerabilities and alternative production portfolios. In this research, a robust RMS reconfiguration strategy is designed using a compromise decision support problem (cDSP), and decentralised decision-making designs are explored through the use of game theory. The findings provide a new production system for adaptable, responsive, and sustainable manufacturing processes in the dynamic global economy. These results can empower stakeholders to make timely design decisions that lead to significant cost savings and sustainable manufacturing