Loyalty programs (LPs) are an important marketing instrument used to promote repeat purchases and customer relationships. Although numerous studies have shed light on the adoption, design, and ...outcomes of LPs, research that reviews the accumulated knowledge in a holistic manner is sparse. Against this background, this study reviews 131 LP-related articles following the Theory–Context–Characteristics–Methodology (TCCM) review protocol. By considering the theories, contexts, characteristics, and methodologies used in LP research, this study (1) paints the most comprehensive picture of the field to date and (2) develops a future research agenda to help advance the field further. Our review reveals that existing studies mostly rely on status-based, inertia-based, or relationship-based mechanisms to theoretically explain LP-related effects, while multi-theoretical perspectives are rare. LP research focuses strongly on a few key industries, such as retail, airlines, and hotels, but lacks insights into the design and outcomes of LPs in online and B2B contexts. Furthermore, we diagnose a need for more research on the role of competition among LPs and the impact of recent technological advances on LP management.
As a magical material with powerful functions, graphene has recent high strength, excellent thermal conductivity, and good biological compatibility. In recent years, it has attracted the attention of ...the scientific and public worlds. Considering the prospects of extensive research in graphene, this paper uses the results of the predecessor used in the panoramic method to summarize the research and application of graphene. Specifically, this paper introduces the basic information of graphene including the simple concepts, structures, and main preparation methods. The advantages and weaknesses of different preparation methods (Mechanical Exfoliation Method, Redox method, Exogenous extension method (SiC), Liquid Phase Epitaxy, Vapor deposition method, and Solvothermal method) are compared. In terms of applications, this paper summarizes graphene applied in the current anode materials of the battery, and the field of medical application (dental planting, bone tissue engineering project). The current production rate of graphene is low, the quality of graphene is not high, and the quality of graphene is low. On this basis, and the aspect of the performance of graphene improvement has been outlooked.
Gas storage capacity and gas producibility of shale gas reservoirs are critically limited by shale porosity. In spite of its importance, porosimetric characterization of shale remains challenging due ...to highly heterogeneous structures, small average pore sizes, and wide pore size distributions. This study utilizes low-pressure N2 and CO2 gas adsorption porosimetry to investigate the evolution of micro- and mesopores in a suite of 11 New Albany Shale samples across a wide range of thermal maturity corresponding to vitrinite reflection Ro values from 0.35 to 1.41%. Mesopore volumes follow a nonlinear evolutionary path starting with a maximum in immature shale (sample 472-1). Subsequent intermittent minima in mesopore volumes during early and late maturity are consistent with the transformation of kerogen during the early mature stage (sample 554-2) and secondary cracking of bitumen/oil at the late mature stage (sample IL2), respectively. Micropore volumes display a varying trend throughout thermal maturation, and are significantly controlled by total organic carbon contents. Both meso- and micropore volumes are positively correlated with clay content and tend to decrease with an increase in feldspar content.
A reduction in grain size of shale samples for gas adsorption porosimetry prominently enhances mesopore volumes, whereas the effects on micropore volumes are variable. These findings may be associated with the fact that smaller particles are able to attain complete adsorption equilibrium quickly, which in turn reduces experimental artefacts during gas adsorption porosimetry. Crushing of shale not only alters the shape of gas adsorption hysteresis loops, but also tends to tighten the openings of hysteresis loops by enhancing the connectivity of pores and reducing the likelihood of gas being trapped during desorption.
•The use of smaller shale particle size in gas adsorption porosimetry enhances mesopore volumes.•The crushing of shale samples below 20 mesh improves pore accessibility and the validity of porosimetric data.•Crushing alters the shape and tightens the openings of hysteresis loops at low P/Po.•The evolution of micro- and mesopore volumes is largely influenced by organic matter transformation.
Using hand-collected data on changes of government officials in 277 Chinese cities, we examine how political turnover affects corporate investment in a transitional economy. We find that political ...turnover leads firms to significantly reduce corporate investment, particularly when the new official is an outsider appointed by a higher level government. The effect of political turnover on corporate investment is stronger for state-owned enterprises, capital intensive firms, and firms deemed locally important. Overall, the volatility of corporate investment increases with political turnover. Finally, the investment decline due to political turnover has significantly negative impact on the profitability of private firms, but not state-owned firms.
•Political turnover leads firms to significantly reduce corporate investment.•The reduction is more pronounced for state-owned enterprises, capital intensive firms, and firms deemed locally important.•Outsider appointment has more significant impact on investment than local promotion.•Volatility of corporate investment increases with political turnover.•Investment decline due to political turnover hurts the profitability of private firms.
•We demonstrate the applicability of micro-FTIR to quantify shale mineralogy.•Characteristic peaks for minerals and kerogen in shales allow fast and reliable FTIR quantifications.•Micro-FTIR offers ...in situ quantification at high resolution of shales.
Fine-grained texture, complex mineralogical composition, and diverse organic matter types cause large heterogeneity of shale, and the resulting analytical challenge can only be met with high-resolution techniques. Quantitative determination of clay minerals, quartz and carbonates, as well as organic matter in shale on a micrometer-scale is demonstrated by traditional KBr-Fourier transform infrared (FTIR) spectroscopy and novel reflectance micro-FTIR techniques, respectively, the latter allowing characterization and mapping of areas as small as 20×20μm. Advantages and limitations of FTIR techniques are discussed mainly with reference to the study of shale, but are relevant also for other fine-grained materials.
Fourier transform infrared spectra of a suite of coals of varying rank from peat to anthracite were obtained via reflectance micro-FTIR and traditional KBr pellet techniques. With increasing rank of ...coal samples, KBr-FTIR spectra exhibit rising aromaticity (ratio of CHar at 3000–3100 or 700–900cm−1 versus CHal at 2800–3000cm−1) and enhanced condensation of aromatic rings (ratio of CHar versus C=C at ~1600cm−1), whereas the aliphatic chain length (ratio of CH2/CH3 at 2800–3000cm−1) and the ‘C’ factor (ratio of C=O at ~1710cm−1 versus (C=O+C=C)) decrease. The ratio of CHal /(CHal+C=C) (i.e., the ‘A’ factor), which reflects the hydrocarbon-generating potential, initially rises at low rank and later decreases in higher-rank coal= (Ro >0.98%). However, the trends of these semi-quantitative FTIR ratios are difficult to trace in high-rank coals (Ro >1.50%), probably attributable to limited peak areas and enhanced uncertainties in ratio calculations. The overall evolutionary trends of functional group abundances in bulk coals and their individual macerals are similar; distinct differences in chemical properties, however, exist among maceral groups, and these variations depend on rank. Within the three maceral groups, liptinite generally exhibits the lowest aromaticity, the longest aliphatic chains having the least amount of branching, and the highest ‘A’ factor testifying to the highest hydrocarbon-generating potential. In contrast, inertinite shows the highest aromaticity and degree of condensation of aromatic domains and the lowest hydrocarbon-generating potential. Vitrinite generally exhibits intermediate characteristics between liptinite and inertinite.
Compared to KBr spectra, micro-FTIR spectra present better detection capability and stronger signals in the 700–900cm−1 region, which allows for close investigation of aromatic CHx out-of-plane deformation modes. The rapid decrease in the peak area ratio at ~870cm−1/~750cm−1 in vitrinite from peat to low-volatile bituminous coal is followed by a significant increase after Ro >1.50%, which indicates the dominance of highly substituted aromatic rings in immature coal's structure, while condensed aromatic domains become prevalent in higher-rank coals (semi-anthracite and anthracite). The increase in coal aromaticity during coalification is attributed largely to the accumulation of condensed aromatic structures in more mature coals. Novel reflectance micro-FTIR mapping is a promising and powerful tool providing high-resolution information on chemical properties of coal macerals relating to parent material and coalification.
► We demonstrate the applicability of micro-FTIR mapping to the study of coal macerals. ► Aromaticity increases and aliphatic chain length decreases with coal rank. ► Highly substituted aromatic rings dominate in immature coal’s structure. ► Condensed aromatic domains are prevalent in higher-rank coals.
•We quantitatively explore the impacts of COVID-19 on the usage of bike sharing.•A novel method is proposed to estimate trip distances and trajectories of bike sharing.•Complex network theory is ...employed to explore the transformation of user behaviors.•COVID-19 impacts the user behaviors and environmental benefits of bike sharing significantly.
The COVID-19 pandemic spreads rapidly around the world, and has given rise to huge impacts on all aspects of human society. This study utilizes big data techniques to analyze the impacts of COVID-19 on the user behaviors and environmental benefits of bike sharing. In this study, a novel method is proposed to calculate the trip distances and trajectories via a python package OSMnx so as to accurately estimate the environmental benefits of bike sharing. In addition, we employ the topological indices arising from complex network theory to quantitatively analyze the transformation of user behavior pattern of bike sharing during the COVID-19 pandemic. The results show that this pandemic has impacted the user behaviors and environmental benefits of bike sharing in Beijing significantly. During the pandemic, the estimated reductions of energy consumption and emissions on 6th Feb decreased to approximately 1 in 17 of those on a normal day, and the environmental benefits at most recovered to 70% of those in normal days. The impacts of COVID-19 on the environmental benefits in different districts are different. Furthermore, the decline of average strength and strength distribution obeying exponential distribution but with different slope rates suggests that people are less likely to take bike sharing to the places where were popular before. The pandemic has also increased the average trip time of bike sharing. Our research may facilitate the understanding of the impacts of COVID-19 pandemic on our society and environment, and also provide clues to adapt to this unprecedented pandemic so as to respond to similar events in the future.
•Beijing rail transit network is a typical scale-free network.•The external perturbation is larger, the time of all stations failure is earlier.•With the increasing of flow coupling coefficient, risk ...stations will transfer.•The threshold with loop line attacked is smaller than straight line.•The vulnerability of BRTN under loop line attacked is more prominent.
Rail transit network (RTN) has become the core of urban public transport system. Because RTN’s topological structure has become complicated with its scale, the phenomenon of overload operation frequently appears at stations or lines, reducing the stability of RTN in operation. There is a need to identify the key stations and to analyze the vulnerability of RTN in depth.
This paper quantitatively analyzes statistical topology parameters of Beijing rail transit network (BRTN) based on complex network theory (CNT). The key stations are evaluated by different evaluation indicators, such as node degree, betweenness, and strength. Then, a model is proposed to analyze the cascading failures of weighted BRTN considering loading and redistribution of multi-static passenger flow based on coupled map lattices (CML).
Results show that when the external perturbation is larger, the time of all stations failure is earlier once the failure is triggered. Moreover, the perturbation threshold for the cascading failure of weighted BRTN is determined. Transfer regularities of the risk stations in BRTN are researched under different combinations of the topological coupling coefficients and the flow coupling coefficients. Under attack, the threshold of loop line damaged is smaller than a straight line. And, while attacking the loop line, the discrete degree of peak time and all station failure time are higher under different perturbations, meaning that failure is hard to control.
This study provides recommendations on developing strategies for RTN design and performance evaluation. Future studies will focus on the coordination of weighted complex public transit networks other than passenger flow redistribution within RTN.
Porosity in shales is important for storage of shale gas in reservoirs. As organic-rich shale thermally matures and enters the oil window, generated bitumen and oil can fill pore spaces, block pore ...connectivity, and reduce porosity. Low-pressure N2 and CO2 adsorption techniques were used to quantify mesoporosity (pore size 2–50nm, accessible to N2 and CO2) and microporosity (pore size <2nm, accessible to CO2 only) in New Albany Shale samples of Devonian and Mississippian age from Indiana and Illinois ranging from marginally mature (vitrinite reflectance Ro=0.55%) to post-mature (Ro=1.41%). After measuring their original porosity, the shale samples were Soxhlet-extracted in refluxing dichloromethane (DCM, boiling temperature 39.6°C) to remove soluble oil/bitumen, vacuum-dried, and then re-measured for meso and microporosities. Subsequently, the same samples were Soxhlet-extracted in toluene (boiling temperature 111°C, with enhanced solubility of oil/bitumen), vacuum-dried, and again characterized porosimetrically.
The maturation sequence of the original, non-extracted shales expresses a higher mesoporosity in lower maturity samples (vitrinite reflectance Ro 0.55%, and 0.65%), and an intermittent decrease in mesoporosity in samples of post-mature stage (Ro 1.15%) in two size fractions (4-mesh and 60-mesh). The intermittent decrease in mesoporosity is consistent with partial filling of pore spaces with bitumen and oil until secondary cracking reclaims some of the lost open pore space from liquid hydrocarbon phases. Organic matter (OM) transformation is thus a pivotal cause for the observed evolution of mesoporosity in original, non-extracted shales. Micropore volumes display a varying trend throughout thermal maturation, and are significantly controlled by total organic carbon content. Compared to 4-mesh sample fractions, a reduction in grain size of 60-mesh fractions for gas adsorption porosimetry prominently enhances mesopore volumes, whereas the effects on micropore volumes are variable. These findings may be associated with the fact that for smaller particles it is easier to attain equilibrium during gas adsorption porosimetry.
Solvent extraction of soluble bitumen and oil from the shale samples generally opens additional pore space for N2 and CO2 adsorption, although the specific effects on mesoporosity and microporosity depend on maturity, total organic carbon (TOC) content, type of solvent, and grain size of the Soxhlet-extracted shales. The mesopore volume increases more in extracted samples with higher maturity, whereas the strongest gain in micropore volume is observed at elevated TOC content and highest maturity.
Comparative porosities of original and Soxhlet-extracted shale samples constrain the evolution of porosity along maturation, as well as the effect of partial oil/bitumen filling and blocking of pores. This study also employs FTIR analyses of DCM and toluene Soxhlet extracts to differentiate low-temperature DCM-extractable, mostly aliphatic OM from higher-temperature toluene-soluble OM containing condensed cross-linked polyaromatic structures.
Fourier transform infrared spectroscopy (FTIR) can provide crucial information on the molecular structure of organic and inorganic components and has been used extensively for chemical ...characterization of geological samples in the past few decades. In this paper, recent applications of FTIR in the geological sciences are reviewed. Particularly, its use in the characterization of geochemistry and thermal maturation of organic matter in coal and shale is addressed. These investigations demonstrate that the employment of high-resolution micro-FTIR imaging enables visualization and mapping of the distributions of organic matter and minerals on a micrometer scale in geological samples, and promotes an advanced understanding of heterogeneity of organic rich coal and shale. Additionally, micro-FTIR is particularly suitable for in situ, non-destructive characterization of minute microfossils, small fluid and melt inclusions within crystals, and volatiles in glasses and minerals. This technique can also assist in the chemotaxonomic classification of macrofossils such as plant fossils. These features, barely accessible with other analytical techniques, may provide fundamental information on paleoclimate, depositional environment, and the evolution of geological (e.g., volcanic and magmatic) systems.
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