With the spread of the COVID-19 pandemic and the implementation of closure measures in 2020, population mobility and human activities have decreased, which has seriously impacted atmospheric quality. ...Huaibei City is an important coal and chemical production base in East China, which faces increasing environmental problems. The impact of anthropogenic activities on air quality in this area was investigated by comparing the COVID-19 lockdown in 2020 with the normal situation in 2021. Tropospheric NO2, HCHO and SO2 column densities were observed by ground-based multiple axis differential optical absorption spectroscopy (MAX-DOAS). In situ measurements for PM2.5, NO2, SO2 and O3 were also taken. The observation period was divided into four phases, the pre-lockdown period, phase 1 lockdown, phase 2 lockdown and the post-lockdown period. Ground-based MAX-DOAS results showed that tropospheric NO2, HCHO and SO2 column densities increased by 41, 14 and 14%, respectively, during phase 1 in 2021 vs. 2020. In situ results showed that NO2 and SO2 increased by 59 and 11%, respectively, during phase 1 in 2021 vs. 2020, but PM2.5 and O3 decreased by 15 and 17%, respectively. In the phase 2 period, due to the partial lifting of control measures, the concentration of pollutants did not significantly change. The weekly MAX-DOAS results showed that there was no obvious weekend effect of pollutants in the Huaibei area, and NO2, HCHO and SO2 had obvious diurnal variation characteristics. In addition, the relationship between the column densities and wind speed and direction in 2020 and 2021 was studied. The results showed that, in the absence of traffic control in 2021, elevated sources in the Eastern part of the city emitted large amounts of NO2. The observed ratios of HCHO to NO2 suggested that tropospheric ozone production involved NOX-limited scenarios. The correlation analysis between HCHO and different gases showed that HCHO mainly originated from primary emission sources related to SO2.
A new and general method for the synthesis of β-azidosulfonates has been achieved through Cu(I)-mediated radical oxidative sulfonylation–azidation of alkenes with sodium sulfinates. Under identical ...conditions, azido fluoroalkyated products could be readily obtained instead using CF3SO2Na or CHF2SO2Na as reagents. The starting materials of sulfinate compounds, alkenes, and azidotrimethylsilane are stable and cheap. This method can be easily adapted for large-scale preparation.
Carbon dioxide (CO2) is one of the most important anthropogenic greenhouse gases (GHG) and significantly affects the energy balance of atmospheric systems. Larger coverage and higher spatial ...resolution of CO2 measurements can complement the existing in situ network and satellite measurements and thus improve our understanding of the global carbon cycle. In this study, we present a self-made airborne infrared remote sensing spectrometer (Air-IRSS) designed to determine the regional distribution of CO2. The Air-IRSS measured CO2 in the spectral range between 1590 and 1620 nm at a spectral resolution of 0.45 nm and an exposure time of 1 s. It was operated onboard an aircraft at a height of 3 km with a velocity of 180 km/h, and a spatial resolution of 50.00 m × 62.80 m. Weighting function modified differential optical absorption spectroscopy (WFM-DOAS) was used to analyze the measured spectra. The results show that the total uncertainty estimated for the retrieval of the CO2 column was 1.26% for airborne measurements over a large region, and 0.30% for a fixed point, such as power points or factories. Under vibration-free static conditions, the on-ground Air-IRSS observations can adequately reproduce the variations observed by Greenhouse Gases Observing Satellite (GOSAT) with a correlation coefficient (r) of 0.72. Finally, we conducted an airborne field campaign to determine the regional distribution of CO2 over the North China Plain. The regional distribution of CO2 columns over four cities of Xing-tai, Hengshui, Shijiazhuang, and Baoding were obtained with the GPS information, which ranged from 2.00 × 1021 molec cm−2 to 3.00 × 1021 molec cm−2. The CO2 vertical distributions were almost uniform below a height of 3 km in the area without CO2 emission sources, and the highest values were found over Baoding City.
A photoinduced decarboxylative three‐component coupling reaction involving amine, maleic anhydride, and fluorinated alkyl iodides has been developed, leading to synthetically valuable ...fluoroalkyl‐containing acrylamides with a high E selectivity. A broad array of substrates including monoprotected amino acid are capable coupling partners. Preliminary mechanistic studies suggest a stepwise process. This reaction represents the first example of photoinduced decarboxylative difunctionalization of maleic anhydride.
Go photo! A photoinduced decarboxylative three‐component coupling reaction involving amine, maleic anhydride, and fluorinated alkyl iodides has been developed, leading to synthetically valuable fluoroalkyl‐containing acrylamides with a high E selectivity. A broad array of substrates including monoprotected amino acid are capable coupling partners. Preliminary mechanistic studies suggest a stepwise process.
We simulated instrumental line shape (ILS) degradations with respect to
typical types of misalignment, and compared their influence on each NDACC
(Network for Detection of Atmospheric Composition ...Change) gas. The
sensitivities of the total column, the root mean square (rms) of the fitting residual,
the total random uncertainty, the total systematic uncertainty, the total uncertainty,
degrees of freedom for signal (DOFs), and the profile with respect to different
levels of ILS degradation for all current standard NDACC gases, i.e. O3, HNO3, HCl, HF, ClONO2, CH4, CO, N2O,
C2H6, and HCN, were investigated. The influence of an imperfect ILS
on NDACC gases' retrieval was assessed, and the consistency under different
meteorological conditions and solar zenith angles (SZAs) were examined. The
study concluded that the influence of ILS degradation can be approximated by
the linear sum of individual modulation efficiency (ME) amplitude influence
and phase error (PE) influence. The PE influence is of secondary importance
compared with the ME amplitude. Generally, the stratospheric gases are more
sensitive to ILS degradation than the tropospheric gases, and the positive ME
influence is larger than the negative ME. For a typical ILS degradation
(10 %), the total columns of stratospheric gases O3, HNO3, HCl,
HF, and ClONO2 changed by 1.9, 0.7, 4, 3, and 23 %,
respectively, while the columns of tropospheric gases CH4, CO, N2O,
C2H6, and HCN changed by 0.04, 2.1, 0.2, 1.1, and
0.75 %, respectively. In order to suppress the fractional difference in the total column for ClONO2 and other NDACC gases within 10 and 1 %,
respectively, the maximum positive ME degradations for O3, HNO3,
HCl, HF, ClONO2, CO, C2H6, and HCN should be less than 6,
15, 5, 5, 5, 5, 9, and 13 %, respectively; the
maximum negative ME degradations for O3, HCl, and HF should be less than
6, 12, and 12 %, respectively; the influence of ILS degradation on
CH4 and N2O can be regarded as being negligible.
Edge localized mode (ELM) mitigation accompanied by density pump-out has been achieved during the application of resonant magnetic perturbation (RMP) with a toroidal mode number of n = 4 on EAST ...recently. The mean ELM frequency increases by a factor of 2.7 from 86 to 235 Hz with a decreased reduction in ELM loss. The evolution of pedestal electron density measured by a profile reflectometer before and after turning on the RMP current is presented. Both the pedestal density and density gradient show a decrease with application of RMP. The density fluctuation in the pedestal region has been measured by an O-mode fluctuation reflectometer. The broadband density fluctuation with a frequency range of 20–115 kHz is enhanced at the later period of the inter-ELM phase during ELM mitigation. This phenomenon is also observed for magnetic fluctuation measured by magnetic probes mounted in the vacuum vessel. A further study shows that the enhanced broadband fluctuations lead to a decrease in the growth rate of the pedestal density and an increase in divert or particle flux. This result implies that these enhanced broadband fluctuations could lead to an enhancement of outward particle transport. The possible roles of the enhanced fluctuations observed in ELM mitigation are also discussed.
All superconducting tokamak: EAST Hu, Jiansheng; Xi, Weibin; Zhang, Jian ...
AAPPS bulletin,
12/2023, Letnik:
33, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Experimental Advanced Superconducting Tokamak (EAST) was built to demonstrate high-power, long-pulse operations under fusion-relevant conditions, with major radius
R
= 1.9 m, minor radius
a
= 0.5 m, ...and design pulse length up to 1000s. It has an ITER-like D-shaped cross-section with two symmetric divertors at the top and bottom, accommodating both single null and double null divertor configurations. EAST construction was started in 2000, and its first plasma was successfully obtained in 2006. In the past 15 years, plasma-facing components, plasma heating, diagnostics, and other systems have been upgraded step by step to meet its mission on exploring of the scientific and technological bases for fusion reactors and studying the physics and engineering technology issues with long pulse steady-state operation. An advanced steady-state plasma operation scenario has been developed, and plasma parameters were greatly improved. Meanwhile, front physics on the magnetic confinement plasmas have been systemically investigated and lots of fruitful results were realized, covering transport and confinement, MHD stabilities, pedestal physics, divertor and scrap-off layer (SOL) physics, and energetic particle physics. This brief review of EAST on engineering upgrading, stand-steady operation scenario development, and plasma physics investigation would be useful for the reference on construction and operation of a superconducting tokamak, such as ITER and future fusion reactor.
We report a palladium‐catalyzed formal intermolecular 4+2 cycloaddition of benzoic and acrylic acids with 1,3‐dienes including the stock chemicals 1,3‐butadiene and isoprene leading to synthetically ...useful 3,4‐dihydroisocoumarins and 5,6‐dihydrocoumalins. Stepwise C—H bond cleavage and annulation are likely involved in the reaction pathway. The synthetic potential of the methodology was demonstrated by two short derivatizations and total synthesis of natural product Clausamine B.
We report a palladium‐catalyzed formal intermolecular 4+2 cycloaddition of benzoic and acrylic acids with 1,3‐dienes including the stock chemicals 1,3‐butadiene and isoprene leading to synthetically useful 3,4‐dihydroisocoumarin and 5,6‐dihydrocoumalins. Stepwise C—H bond cleavage and annulation are likely involved in the reaction pathway. The synthetic potential of the methodology was demonstrated by two short derivatizations and total synthesis of natural product Clausamine B.
The compressional magnetic component δB|| has been implemented in the gyrokinetic Particle-in-Cell (PIC) code GEM for the fully electromagnetic simulation of microscopic instabilities in high-β ...tokamak plasmas. The simulation model is formulated for the split-weight scheme that is based on the canonical momentum formulation of the gyrokinetic equation. A pseudo-spectral method is used to solve the coupled gyrokinetic field equations while preserving all finite-Larmor-radius (FLR) effects. The algorithm is verified by the method of manufactured solutions. Simulations of the ion-temperature-gradient-driven (ITG) mode, the kinetic balloon mode (KBM) and the trapped electron mode (TEM) are presented.
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