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Global dairy production, consumption, and trade are growing rapidly, driven by population and per capita income growth and increasing health concerns mainly from developing countries, which has aroused concerns about the related carbon emission (mostly in the form of methane) increase. If all of the dairy products consumed were produced locally/domestically in the developing countries/economies (a counterfactual scenario), the carbon emissions in 2018 would be 28 Mt CO

The recent "US-China trade war" has aroused concern over trade-related environmental impacts. This study built a multiregional computable general equilibrium model to simulate environmental impacts of the "US-China trade war" under different scenarios of tariff and nontariff barriers and the battlefield spreading ranges. The present study found that although the trade war will cause a global economic downturn, which will seemingly reduce environmental pressure globally, global carbon emissions are expected to increase rather than decline. On the one hand, the CO2 emission increase caused by land-use changes in Brazil and Argentina will far exceed the emission reduction because of decreased global production. On the other hand, some countries/economies especially those developing countries such as Vietnam, Russia, and India will face emission increases driven by scale effects. Countries such as Korea, the UK, and France will enjoy a reduction in emissions driven by structural effects. China and the US will face a reduction in production and CO2 emissions, but their CO2 emission intensities will rise. The results remind us that as global production and supply chains are formed, it is important to closely monitor trade-related environmental impacts. Efforts should be made to balance the interests of trade and the environment.

Sparse phase retrieval mainly solves nonconvex and nonsmooth problems. Aiming at the nonsmooth problem in sparse phase retrieval, we propose a smoothing algorithm which is called sparse smoothed amplitude flow (SPSAF). The proposed SPSAF algorithm is an amplitude-based nonconvex sparse smoothing phase retrieval algorithm. First, the original phase retrieval loss function is smoothed without modifying the gradient in the gradient refinement stage, thereby reducing the computational complexity of the overall algorithm. Secondly, the support of the original signal is estimated by differential analysis of the gaps, and the initialization can be obtained through a carefully designed method based on this support. Finally, we get sparse estimates by gradient descent based on hard thresholding. Numerical experiments show that the proposed SPSAF algorithm has significant improvements in recovery performance, convergence speed, and sampling complexity. Further, the SPSAF algorithm is stable in noisy environments.

The enhancement of plasma generation in atmospheric pressure dielectric barrier discharge (DBD) is gaining increasing interest for various plasma applications. In this paper, the effect of surface charges moving with the rotating dielectric plate on improving the generation of streamer channels is investigated by a statistical analysis of electrical measurements, optical diagnostics, and numerical simulation in a needle-plate DBD device with a rotating dielectric plate. Results suggest that rotating the dielectric plate can improve the spatiotemporal distribution of streamer channels by inducing a bending of the streamer channels and an increase in the number of discharges. Statistical results show that the number of current pulse and discharge energy are increased by 20% and 47%, respectively, at the rotating speed of 160 rps (revolution per second). Based on the interaction between the applied electric field and the electric field induced by surface charges, a formula is proposed to govern the effect of rotating the dielectric plate on the discharge energy and streamer bending. To further understand the mechanism of the influence of rotating the dielectric plate on plasma properties, a 2D fluid model is implemented, and the reduced electric field and streamer propagation are analyzed. Results show that the effective transfer and reuse of surface charges play an important role in the enhancement of plasma generation.

The global trade of solar photovoltaic (PV) products substantially contributes to increases in solar power generation and carbon emissions reductions. This paper depicts global PV product trade patterns, explores emissions reduction potential, and evaluates the impeding effect of tariff barriers on global PV product trade and emissions reductions. Solar power generation will result in a reduction of emissions in a range of 50–180 gigatons of carbon dioxide equivalent (GtCO2e) between 2017 and 2060 in a business as usual (BAU) scenario. Compared with BAU, during 2017–2060, global total solar cell and module production and installation will increase by roughly 750 gigawatts (GW) if half of the status quo trade barrier are removed, while it will decrease by 160–370 GW under tensioned trade barrier scenarios. Trade barrier reduction by half from the 2017 status quo level will increase the net carbon emissions mitigation potential by 4–12 GtCO2e by 2060, while extra trade barrier imposition will result in global net carbon emissions mitigation potential decreasing by up to 3–4 GtCO2e by 2060. Well-coordinated policy and institutional reforms are recommended to facilitate PV product trade and to deliver the related global environmental benefits., Global trade of solar photovoltaic (PV) products has an important role to play in sustainable mitigation to climate change. Highlighting global PV product trade, this study explores the impeding effect of tariff and non-tariff barriers on global PV product trade and carbon emissions reductions.

Al-doped porous ZnO hollow micro-spheres were prepared using a sol-gel method with a template of agglomerates of polystyrene (PS) nanospheres, and the composite of these ZnO hollow micro-spheres and Ag nanoparticles was prepared with further photo-deposition. The effects of Al doped on the structure and the optical properties of the specimen were investigated by means of x-ray diffractometer, SEM, TEM, an UV-Vis diffuse reflectance analyzer, and photoluminescence (PL) spectroscopy. Different doping concentrations of Al affect not only the existing form of Al atoms in the crystal but also the concentration of the intrinsic defects of ZnO, thus influencing the morphology of the hollow micro-spheres. The appropriate amount of Al doping provides the hollow spheres with a porous, loose morphology, showing the largest specific surface area, which significantly improves the absorbance of light and the number of reaction sites in photocatalysis. For the composite specimen, the introduction of Ag nanoparticles improves the absorbance of light in the visible region because of the surface plasmon resonance: in the PL measurements, because many electrons in the ZnO crystal flow to the surface of Ag nanoparticles due to the difference of energy levels between Ag and ZnO crystals, the intensity of the intrinsic and defect-related emissions of ZnO is reduced. The photocatalytic properties of the specimens were evaluated with the degradation of a methyl orange dye solution under simulated solar irradiation at room temperature. The specimen of porous ZnO hollow micro-spheres with 3% Al dopant concentration demonstrates excellent photocatalytic performance due to its large specific surface area. However, with the designed energy structure, the composite of porous ZnO hollow micro-spheres and Ag nanoparticles exhibits the best photocatalytic performance among the specimens tested by separating electrons and holes in the ZnO crystal.

ZnO nanorods/g-C3N4 photocatalytic composite was prepared, and its structural and optical properties have been studied. Bulk graphite phase carbon nitride (g-C3N4) was first prepared by a one-step thermal polymerization method, and ZnO nanorods were grown from the ZnO seed particles on the surface of g-C3N4 by a hydrothermal method. The effects of hydrothermal reaction time on the morphology and photocatalytic properties of ZnO nanorods/g-C3N4 composite were investigated. The hydrothermal reaction included two stages. The initial stage was dominated by the rapid deposition of Zn2+ precursor in hydrothermal solution on ZnO seed particles to form ZnO seed layer, and the second stage was the hydrothermal growth of ZnO nanorods from the ZnO seed layer. In the second stage, two processes occurred simultaneously, namely, the dissolution of seed layer and the growth of ZnO nanorods. Hence, the composite prepared with different hydrothermal time shows different photocatalytic degradation mechanism to methyl orange (MO) solution. The photocatalytic performance of the composite sample with the grown time of 2 h is mainly attributed to separation efficiency of photogenerated carriers. For the composite sample with the grown time of 3 h, due to the partial dissolution of seed layer, its photocatalytic performance is mainly attributed to the surface reaction of ZnO nanorods. For the composite samples with the hydrothermal grown time of 4 and 5 h, the dense ZnO nanorods on the surface of g-C3N4 improve the separation efficiency of the photogenerated carriers, and their photocatalytic performance is attributed to both carrier lifetime and surface reaction. As a result of synergy, the sample with the hydrothermal grown time of 3 h shows the best photocatalytic performance in all composite sample.

We modulate the electromagnetic response of terahertz metamaterials by exciting photogenerated carriers with ultra-short pulsed laser, and realize the active control of terahertz transmission and resonances in a wide band. The experimental results show that when the terahertz electric vector is perpendicular and parallel to the bar direction with the open gap in the circular split ring resonators, respectively, the transmission of the non-resonant region and resonance absorption are significantly tuned by the irradiated pump pulse. With the increase of the pump power, the resonance absorption peak decreases and the frequency of resonance dip has a remarkable blue-shift. Meanwhile, the transmission of the non-resonant region decreases correspondingly. It is also found that the blue-shift of the resonance is mainly determined by the change of conductivity and dielectric constant in the photoexcited layer of the substrate. Through the numerical simulation, we have further proved the introduction of pump light has a significant modulation effect on the electromagnetic properties of terahertz metamaterials. Additionally, it can be observed that the LC resonance annihilates earlier than the resonance of the dipole resonance with the increase of pump power, implying the former is particularly sensitive to the variation of the active control. In the theoretical analysis, based on the Lorenz oscillator model, we have derived and calculated the resonance response intensity of the coupled oscillators under an external field. The calculated results indicate the coupling coefficient and damping rate have an impact on the spectra evolution, showing that the resonant response peak has a remarkable blue-shift with the increase of coupling coefficient and the resonance response intensity decreases with the increase of damping rate.

Highly sensitive response of anisotropic terahertz metamaterials to electromagnetic waves has attracted considerable attention due to its potential applications in terahertz modulators and biosensing devices. We designed three microstructure samples with split ring arrays. The terahertz transmission spectra are experimentally measured at different rotation angle. It is found that as the rotation angle increases, the resonance mode has gradually evolved from a single dipole oscillation mode to the double oscillation modes accompanied with LC and dipole oscillations, we further simulated the polarization conversion characteristics of the single splitting rings. It shows that the highest conversion efficiency appears at 45 degrees. But it doesn’t have polarization conversion effect at 0° and 90°. Subsequently, we have utilized ultrashort pulse laser to optically control the electromagnetic response by exciting the photogenerated carriers in the metamaterial samples. The experimental data show that the transmittance change obviously with the pump light. Additionally, when the angle is 90 degrees, it can be observed that the LC resonance annihilates earlier than the resonance of the dipole resonance with the increase of pump power, implying the former is particularly sensitive to the variation of the dielectric environment. To further explore the influence of dielectric environment on the resonance characteristics of the terahertz metamaterials, we have further performed the simulations with the applied surface analyte of different refractive index. The simulated data show that with the increase of the refractive index of the surface analyte, the resonance frequency of the dipole oscillation has a more significant blue shift than the resonance frequency of the LC oscillation. Our obtained results could provide the idea for designing terahertz modulators and sensitive biosensing devices.

In this paper, a wire-tube electrode system is used to simulate the pollution characteristics of ground materials for HVDC transmission lines. The results show that under the same experimental conditions, the pollution mass of the ground conducting materials is greater than that of the ground insulating materials, and the pollution mass of the ground materials after the corona discharge is significantly greater than that of the ground material before the corona discharge. With the increase of pollution accumulation time, the intensity of corona discharge increases gradually, the pollution rate on the ground conducting materials increases gradually, and the pollution rate on the ground insulating materials decreases gradually. The pollution mass increases linearly with the concentration of particulate matter before corona discharge, while with the increase of the concentration of particulate matter, the pollution mass shows a trend of gradually saturation after corona discharge. With the increase of conductor diameter, the pollution mass of the ground materials decreases gradually. By covering the dielectric film on high-voltage conductor, pollution can be obviously inhibited.

In the teaching of software engineering for computer related majors, there is a gap between high-level logic design and implementation, which leads to the students' unreasonable software design, and the implementation code does not follow the design scheme. Therefore, it is necessary to carry out heuristic teaching for students, starting from the programming students are most familiar with, gradually transition to software design, using reverse thinking teaching mode, so that students can master the transformation relationship between design and implementation. In the implementation of case teaching, it is necessary to restore high-level design or demand analysis through code, realize the conversion from code to document, and effectively improve the theoretical level of students; in terms of practical skills, implement task driven teaching, deepen the understanding of cases and knowledge transfer, and exercise the practical ability of students. Through the performance analysis of 2015 and 2016 students, the reverse engineering case teaching and task driven practice can significantly improve students' practical ability, stimulate students' enthusiasm for software development, and highlight students' software development ability in computer skills competition, college students' innovation training project and graduation design.

The mechanisms of streamer generation and propagation in double-sided pulsed surface dielectric barrier discharge (SDBD) on both sides have been analyzed and investigated by experiment and numerical simulation. The fully exposed asymmetric SDBD has two discharge processes located on the high voltage electrode (HVE) side and the ground electrode (GE) side. Discharge images of the HVE side and GE side are taken by a digital camera under continuous pulse and ICCD (Intensified Charge Coupled Device) is utilized to diagnose the generation and propagation of streamers in single pulse discharge. In order to understand the physical mechanisms of streamer evolution more deeply, we establish a 2D simulation model and analyze it from the aspects of electron density, ion density, reduced electric field and electron impact ionization source term. The results show that the primary and secondary discharges on the HVE side and the GE side of the double-sided SDBD are composed of positive streamer and negative streamer, respectively. On the HVE side, the accumulation of positive charges on the dielectric surface causes the direction of the electric field to reverse, which is the principal factor for the polarity reversal of the streamer. On the GE side, both the negative charges accumulated on the dielectric surface and the falling voltage are the key factors for the streamer polarity switch.

Discharge dynamics of primary and secondary streamers in a repetitively pulsed surface dielectric barrier discharge (SDBD) are investigated based on experimental and numerical simulations. Plasma propagation and coupled energy of the primary streamer are restricted in subsequent pulses, but the deposited energy of the secondary streamer increases. When the pulse repetition frequency reduces, a longer plasma length and higher average velocity of the primary streamer can be observed, but the influences on propagation length and velocity of the secondary streamer are very limited. These phenomena indicate that the residual surface charges left by the previous pulse should have a critical effect on the discharge dynamics of subsequent discharges. In order to have a deeper insight into the influence of residual surface charges in a repetitively pulsed SDBD, a numerical model characterized with a pre-charging of homogeneous charge accumulated on the dielectric surface is built. Pre-charging of positive charges deposited on the dielectric surface can inhibit the electric field of applied voltage, resulting in a decrease in the expansion of the primary streamer and the positive peak of current, which is in qualitative agreement with the experimental measurements. However, there is an opposite evolution rule when the negative charges are deposited on the dielectric surface. Although the electric field strength of the secondary streamer is enhanced for a high pre-charging value, there is no great impact on the negative peak of current during the secondary streamer due to the remaining heavy mass ions.

The effect of oxygen vacancy (VO) defect regeneration in ZnO nanorods on their photocatalytic properties has been investigated. The ZnO nanorods with different VO defect concentrations were realized by the annealing in the different atmospheres of vacuum, oxygen, air and Ar. And the VO defect concentrations in the annealed ZnO nanorods follow an order of Cvacuum > CAr > Cair > Coxygen. By the photocatalytic degradation test to methyl orange solution (MO), the photocatalytic performance of the samples is in accordance with the order of VO defect concentration in the samples, that is, the photocatalytic performance of ZnO nanorods increases with the increase of VO defect concentration, and the best performance is achieved in the sample annealed in the vacuum atmosphere due to the highest VO defect concentration. The regeneration ability of VO defects in ZnO nanorods was studied through the oxygen-deficit atmosphere annealing after each cyclic photocatalytic test. Although the photocatalytic performance of ZnO nanorods degrades slightly with the increase of cyclic test numbers, the VO defects regenerated sample still shows excellent photocatalytic performance after three cyclic tests. The results show that the VO defects in ZnO nanorods play a key role in improving the photocatalytic degradation performance, and the VO defects regenerated ZnO nanorods still show good photocatalytic degradation performance, indicating that ZnO can be reused as a photocatalyst by the VO defect regeneration.

The global trade of solar photovoltaic (PV) products substantially contributes to the increases in solar power generation and carbon emission reduction. This paper depicts the global PV product trade patterns and explores the emissions reduction potential, evaluates the impeding effect of tariff barriers on global PV product trade and the emissions reduction. In 2014 and 2017, the application of traded solar cells and modules resulted in emissions reductions of up to 840.71 and 1,734.59 Mt CO2e as well as substantial reductions in local pollutants. From 2017 to 2050, traded solar cells and modules will result in an approximately 55.76-86.45 Gt CO2e reduction. Extra-tariff imposition in its worst situation will result in global PV applications decreasing by 7.06% and carbon emissions mitigation potential decreasing by 5.09-7.89 Gt CO2e by 2050. Well-coordinated policy and institutional reforms are recommended to facilitate PV product trade and deliver related global and local environmental benefits.

The combination of a multistage rod plasma reactor and post CeO