A method for analyzing pollution control policies: Application to SO2 emissions in China

Market-based pollution control mechanisms such as pollution levy and cap and trade have received increasing attention from both academics and practitioners. A good understanding of the optimal pollution price under these mechanisms is a premise for regulators to make sound pollution control policies. In this paper, we propose a method for deriving the optimal pollution price for a given pollution target. This method consists of two steps that integrate cost function estimation and market equilibrium analysis: First, historical data is used to estimate the pollution abatement cost functions of the polluters; second, market models are used to solve the equilibrium pollution price under each control mechanism. For illustration, we apply the method to investigate SO₂ emission control policies in China, using a dataset of SO₂ emissions and abatement costs from three major industry sectors (Electricity, Gas, and Water Supply; Manufacturing; and Mining). Our analysis shows that the optimal levy rate is significantly higher than the actual rate adopted by the Chinese government. For example, the optimal levy rate should be 4.92 RMB/kg, while the actual rate is 1.26 RMB/kg in 2010. As a result, the actual emission structure is much less efficient: The overall cost savings would be 49.7% for all three sectors during 2006–2010 if the optimal emission structure is achieved. These findings have useful policy implications for the Chinese government. In addition, the method may be applied to analyze control policies at different aggregate levels (for example, provincial economies) or for other pollutants (for example, CO₂ and chemical oxygen demand).     

Ga2O3/HSSZ-13 for dehydrogenation of ethane: Effect of pore geometry of support

Dehydrogenation of ethane to ethylene in the presence of CO₂ was investigated over gallium oxide supported on HSSZ-13 with different Si/Al ratios. These catalysts exhibited higher activity as well as higher selectivity in comparison to HZSM-5 supported ones. 34% ethane conversion with 86.9% selectivity to ethylene could be obtained. The enhanced catalytic performance of Ga₂O₃/HSSZ-13 can be attributed to unique pore geometry of SSZ-13 support. However, the stability is not as good as that of Ga₂O₃/HZSM-5, owing to easy coking in channel with smaller pore-opening size.     

Phenyl Ethylammonium Iodide introduction into inverted triple cation perovskite solar cells for improved VOC and stability

The efficiency of more than 25% in organic-inorganic hybrid perovskite solar cells has made them very attractive in the pursuit of cheaper alternatives to Si-based devices. However, the stability of the perovskite solar cells was challenging, given their high susceptibility to moisture. Very few reports have emerged in this regard that investigated the influence of introducing large cations into a triple cation perovskite (TC-PVS), with several studies limited to single and dual cation perovskites. Further, the crystallization of TC-PVS on a polymer surface such as PEDOT is not straightforward, and their inclusion in inverted solar cell devices was limited. In this work, we investigated the impact of incorporating Phenyl ethyl ammonium cation into FAMACs triple cation composition. We demonstrated improvements in the crystallinity and more uniform coverage with little to no pinholes and smooth morphology for an optimum PEA amount of 1.67% in the precursor solution. The superior morphology, along with a passivation effect from a quasi 2D phase, led to increased photoluminescence and minority carrier lifetimes. Corresponding inverted photovoltaic devices prepared with PEA showed increased open-circuit voltage from 0.89 V for a control sample to 0.95 V for 1.67% PEA and 0.98 V for 5% PEA, doped devices in an inverted configuration. The efficiency, as a result, increased from 11.27% for a control device to 14.85% for a 1.67% PEA doped device. Further, PEA doped devices showed improved operational and thermal stability attributed to the higher moisture tolerance and light-soaking ability of the PEA doped TC-PVS compared to the undoped TC-PVS.     

矩量法-物理光学混合算法计算多尺度复合目标电磁散射场

基于电流的矩量法（method of moments，MoM）和物理光学法（physical optics，PO）的混合算法是目前求解电中尺度和多尺度目标电磁散射和辐射的主要方法，在计算MoM区和PO区的耦合作用时需要对PO区域进行亮区判断.传统纯CPU亮区判断方法时间复杂度为O（N2），时间消耗随着面片数量N增加而急剧增大.文中通过GPU渲染功能及对深度缓冲区（zbuffer）的利用，对PO亮区判断过程进行加速，亮区消耗时间与面片数量无直接联系，在面片数量达到105数量级以上加速优势明显.将加速的MoM-PO混合方法应用于复杂目标与粗糙面的组合情况，对比多层快速多级子（multi level fastmultipole method，MLFMA）方法，相比于纯PO方法，获得较高的精度.相比于单一算法，混合算法有明显优势.     

High-resolution FIB-TEM-STEM structural characterization of grain boundaries in the high dielectric constant perovskite CaCu3Ti4O12

In this work, the grain boundaries composition of the polycrystalline CaCu₃Ti₄O₁₂ (CCTO) was investigated. A Focused Ion Beam (FIB)/lift-out technique was used to prepare site-specific thin samples of the grain boundaries interface of CCTO ceramics. Scanning transmission electron microscopy (STEM) coupled with energy dispersive X-ray spectrometry (EDXS) and Electron Energy Loss Spectroscopy (EELS) systems were used to characterize the composition and nanostructure of the grain and grain boundaries region. It is known that during conventional sintering, discontinuous grain growth occurs and a Cu-rich phase appears at grain boundaries. This Cu-rich phase may affect the final dielectric properties of CCTO but its structure and chemical composition remained unknown. For the first time, this high-resolution FIB-TEM-STEM study of CCTO interfacial region highlights the composition of the phases segregated at grain boundaries namely CuO, Cu₂O and the metastable phase Cu₃TiO_4.     

Designing Champion Nanostructures of Tungsten Dichalcogenides for Electrocatalytic Hydrogen Evolution

Fine-tuning strain and vacancies in 2H-phase transition-metal dichalcogenides, although extremely challenging, is crucial for activating the inert basal plane for boosting the hydrogen evolution reaction (HER). Here, atomically curved 2H-WS₂ nanosheets with precisely tunable strain and sulfur vacancies (S-vacancies) along with rich edge sites are synthesized via a one-step approach by harnessing geometric constraints. The approach is based on the confined epitaxy growth of WS₂ in ordered mesoporous graphene derived from nanocrystal superlattices. The spherical curvature imposed by the graphitic mesopores enables the generation of uniform strain and S-vacancies in the as-grown WS₂ nanosheets, and simultaneous manipulation of these two key parameters can be realized by simply adjusting the pore size. In addition, the formation of unique mesoporous WS₂@graphene van der Waals heterostructures ensures the ready access of active sites. Fine-tuning the WS₂ layer number, strain, and S-vacancies enables arguably the best-performing HER 2H-WS₂ electrocatalysts ever reported. Density functional theory calculations indicate that compared with strain, S-vacancies play a more critical role in enhancing the HER activity.     

Unusual Two-Step Assembly of a Minimalistic Dipeptide-Based Functional Hypergelator

Self-assembled peptide hydrogels represent the realization of peptide nanotechnology into biomedical products. There is a continuous quest to identify the simplest building blocks and optimize their critical gelation concentration (CGC). Herein, a minimalistic, de novo dipeptide, Fmoc-Lys(Fmoc)-Asp, as an hydrogelator with the lowest CGC ever reported, almost fourfold lower as compared to that of a large hexadecapeptide previously described, is reported. The dipeptide self-assembles through an unusual and unprecedented two-step process as elucidated by solid-state NMR and molecular dynamics simulation. The hydrogel is cytocompatible and supports 2D/3D cell growth. Conductive composite gels composed of Fmoc-Lys(Fmoc)-Asp and a conductive polymer exhibit excellent DNA binding. Fmoc-Lys(Fmoc)-Asp exhibits the lowest CGC and highest mechanical properties when compared to a library of dipeptide analogues, thus validating the uniqueness of the molecular design which confers useful properties for various potential applications.     

Boosted photogenerated carriers separation in Z-scheme Cu3P/ZnIn2S4 heterojunction photocatalyst for highly efficient H2 evolution under visible light

Developing low-cost, highly efficient and robust photocatalystic hydrogen evolution system is a promising solution to environmental and energy crisis. Herein, a Z-scheme Cu₃P/ZnIn₂S₄ heterojunction photocatalyst was successfully constructed for the first time via a facile solution-phase hybridization method. The optimized Cu₃P/ZIS composite exhibited the highest H₂ production rate of 2561.1 μmol g⁻¹ h⁻¹ under visible light irradiation (>420 nm), which was 5.2 times greater than that of bare ZnIn₂S₄ and even exceeded the photocatalytic performance of Pt/ZIS composite. The apparent quantum yield of 10 wt% Cu₃P/ZnIn₂S₄ can reach 22.3% at 420 nm. The huge boost of photocatalytic hydrogen evolution activity is ascribed to the formation of heterojunction with the built in electric field within Cu₃P/ZnIn₂S₄ and Z-scheme charge carriers transfer pathway, which result in efficient separation and migration of charge carriers. In addition, both experimental and theoretical calculation confirmed that the charge-carriers transfer pathway of Cu₃P/ZnIn₂S₄ photocatalyst follows the Z-scheme mechanism instead of conventional type-Ⅱ heterojunction mechanism. This work is considered helpful for getting a great deal of insight into constructing high-activity and cost-effective transition metal phosphides (TMPs) based photcatalytic hydrogen production system and rationally designing Z-scheme heterojunction photocatalyst.     

Influence of reduction temperature on Ni particle size and catalytic performance of Ni/Mg(Al)O catalyst for CO2 reforming of CH4

Hydrotalcite-derived Ni/Mg(Al)O is promising for CH₄–CO₂ reforming. However, the catalysts reported so far suffer from sever coking at low temperatures. In this work, we demonstrate that a significant improvement of coke-resistance of Ni/Mg(Al)O can be achieved by fine tuning the Ni particle size through adjusting the reduction condition of catalyst. Ni particles having average size within 4.0–7.1 nm are in situ generated by reducing the catalyst at a selected temperature within 923–1073 K. Controllability of Ni particle size is related to the formation of Mg(Ni,Al)O solid solution upon hydrotalcite decomposition. It is found that the catalyst reduced at 973 K exhibits high activity, stability, and coke-resistance even at reaction temperature as low as 773 K. In contrast, the catalyst reduced at 923 K has low activity and deactivates due to Ni oxidation, while those reduced at 1023 and 1073 K suffer from sintering and severe coking. STEM and O₂-TPO reveal that coke deposition is directly proportional to the Ni particle size but becomes negligible at a size below 6.2 nm. It is evidenced that a critical size of about 6 nm is required to inhibit coking effectively. CO₂ temperature-programmed surface reaction indicates that the deposited carbon on small Ni particles can be easily removed by the CO₂ activated at the Ni–Mg(Al)O interfaces, accounting for the better resistance to coking.     

The impact of oil price shocks in the Canadian economy: A structural investigation on an oil-exporting economy

Oil price shocks and monetary policy response by oil producing economies have been the subject of important theoretical investigation in the modern literature. This topic seems to be well grounded since fluctuations in the US dollar, which is affected by US monetary policy, plays an important role in exacerbating run ups and precipitous falls in world oil prices. We investigate the economic consequences of oil price shocks using an open-economy DSGE model that incorporates demand for and supply of oil while allowing for interaction between domestic and foreign monetary policy. Using Canadian and U.S. data, we quantify the relative importance of oil price shocks and monetary policy response on macroeconomic variables. We show that domestic monetary policy is a key channel that accounts for over 40% of discounted variation in domestic output across a 4-year horizon after an oil shock. In contrast, US monetary policy is of lesser importance in propagating oil price shocks on an oil-exporting economy through the international channel.