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The recent paper by Shen et al. (2018) (referred to hereafter as SHEN) made a sweeping statement on the winter haze pollution in Beijing by claiming “Insignificant effect of climate change on winter haze in Beijing”. We argue that the paper contains three serious flaws. Either one of the three flaws can nullify the claim of SHEN.

We propose low-loss, low-crosstalk slab waveguide-to-fiber coupling using multiplane light conversion. For coupling between a 6-mode waveguide and fiber, insertion loss and mode-dependent loss are 0.38 dB and 0.23 dB, respectively, with 7 phase plates

The dicarbonyls glyoxal (Gly) and methylglyoxal (Mgly) are key tracers for the oxidation of volatile organic compounds (VOCs) in the atmosphere, but their atmospheric chemistry in remote forest environments is not well understood. A study was carried out during Jul. 31–Nov. 5 of 2016 at the summit of Mt. Tianjing (1690 m.a.s.l.), a remote mountaintop site in southern China, to measure the levels of Gly and Mgly and explore their sources and fate. During the study period, the average mixing ratios of Gly and Mgly were 509 ± 31 pptv and 340 ± 32 pptv, respectively, with the Gly/Mgly ratios averaging 1.8 ± 0.2. Both the dicarbonyl concentrations and the Gly/Mgly ratios were significantly higher than those observed in other background sites. Production yield calculations and meteorological data analysis indicate that high levels of Gly and Mgly observed at the study site were largely a combined result of rapid in-situ formation and regional transport by prevailing winds. On average, in-situ formation from precursors is estimated to account for 67% of the observed Mgly and about 9% of the observed Gly. There were significant changes in Gly and Mgly mixing ratios among different time periods when air masses from different source regions dominated, indicating contribution of regional transport to the observed dicarbonyl mixing ratios at the study site. Biogenic emissions in eastern China and anthropogenic emissions in the Pearl River Delta region were the two main sources responsible for the dicarbonyls observed at the site during most of the sampling period, but large-scale biomass burning in central China was also important in the late autumn, as supported by a backward trajectory analysis of fire spot data and the identification of biomass burning tracers. This study provides insights into the background atmospheric chemistry and the impact of biogenic and anthropogenic sources on the dicarbonyls speciation.

Extreme PM2.5 and nonmethane hydrocarbon (NMHC) pollution often occurs simultaneously during the winter. To study the formation mechanism of two pollution events in Chengdu from 23 December 2016 to 31 January 2017, we explored the weather conditions, chemical composition, secondary pollutant conversion, aerosol hygroscopic growth, and potential source contribution function (PSCF) during this period. During the study period, the humidity was high (67.9%), the wind speed was low (1.0 m s−1), the height of the planetary boundary layer was low (463.4 m), and the atmosphere remained stationary. The potential source regions of PM2.5 and NMHCs were locally polluted sites in the southwestern and southern regions of Chengdu, affected by the southwesterly air mass trajectories. PM2.5 and sulfur oxidation ratios (SOR), nitrogen oxidation ratios (NOR) and secondary organic aerosol formation potential (SOAP) showed a strong positive correlation. As pollution increased, the conversion from SO2, NOx and NMHCs to sulfate, nitrate and SOAs increased, resulting in an increase in the secondary aerosol concentration. As the relative humidity increases, aerosols begin to undergo rapid hygroscopic growth, which seriously affects the visibility of the atmosphere. In general, pollutant emissions, static weather, and secondary conversion, among other factors, lead to the occurrence of this persistent extreme haze pollution.

Adverse health effects of ambient PM

Let $A$ be the AF algebra whose scaled ordered group $K_{0}(A)$ is $(G\oplus H,(G_{+}\setminus\{0\})\oplus H\cup\{(0,0)\},\tilde{g}\oplus0)$ , where $(G,G_{+},\tilde{g})$ is the scaled ordered group $K_{0}(B)$ of a unital simple AF algebra $B$ , and $H$ is a countable torsion-free Abelian group. Let $\sigma$ be an order 2 scaled ordered automorphism of $K_{0}(A)$ , defined by $\sigma(g,h)=(g,-h)$ , where $(g,h)\in G\oplus H$ . We show that there is an order $2$ automorphism $\alpha$ of $A$ such that $\alpha_{*}=\sigma$ . This gives a partial answer to a lifting question posed by Blackadar. Incidentally, the lift $\alpha$ we construct has the tracial Rokhlin property. Consequently, the crossed product $C^{*}(\mathbb{Z}_{2},A,\alpha)$ is a unital simple AH algebra with no dimension growth.

APHH-Beijing (Atmospheric Pollution and Human Health in a Chinese Megacity) is an international collaborative project to examine the emissions, processes and health effects of air pollution in Beijing. The four research themes of APHH-China are: (1) sources and emissions of urban atmospheric pollution; (2) processes affecting urban atmospheric pollution; (3) exposure science and impacts on health; and (4) interventions and solutions to reduce health impacts. Themes 1 and 2 are closely integrated and support Theme 3, while Themes 1–3 provide scientific data for Theme 4 on the development of cost-effective solutions. A key activity within APHH-Beijing was the two month-long intensive field campaigns at two sites: (i) central Beijing, and (ii) rural Pinggu. The coordinated campaigns provided observations of the atmospheric chemistry and physics in and around Beijing during November–December 2016 and May–June 2017. The campaigns were complemented by numerical air quality modelling and air quality and meteorology data at the 12 national monitoring stations in Beijing. This introduction paper provides an overview of (i) APHH-Beijing programme, (ii) the measurement and modelling activities performed as part of it in Beijing, and (iii) the air quality and meteorological conditions during the two field campaigns. The winter campaign was characterized by high PM2.5 pollution events whereas the summer experienced high ozone pollution events. Air quality was poor during the winter campaign, but less severe than in the same period in 2015 when there were a number of major pollution episodes. PM2.5 levels were relatively low during the summer period, matching the cleanest periods over the previous five years. Synoptic scale meteorological analysis suggests that the greater stagnation and weak southerly circulation in November/December 2016 may have contributed to the poor air quality.

Atmospheric oxidation capacity is the core of converting fresh-emitted substances to secondary pollutants. In this study, we present the in-situ measurements at four Chinese megacities (Beijing, Shanghai, Guangzhou, and Chongqing) in China during photochemical polluted seasons. The atmospheric oxidation capacity is evaluated using an observational-based model with the input of radical chemistry precursor measurements. The radical budget analysis illustrates the importance of HONO and HCHO photolysis, which contribute nearly half of the total radical primary sources. The radical propagation is efficient due to abundant of NO in the urban environments. Hence, the production rate of secondary pollutants, i.e. ozone and fine particle precursors (H2SO4, HNO3, and ELVOCs) is fast resulting in secondary air pollution. The ozone budget demonstrates that strong ozone production occurs in the urban area which results in fast ozone concentration increase locally and further transported to downwind areas. On the other hand, the O3-NOx-VOC sensitivity tests show that ozone production is VOC-limited, among which alkenes and aromatics should be first mitigated for ozone pollution control in the presented four megacities. However, NOx emission control will lead to more server ozone pollution due to the drawback-effect of NOx reduction. For fine particle pollution, the role of HNO3−NO3− partitioning system is investigated with a thermal dynamic model (ISORROPIA2) due to the importance of particulate nitrate during photochemical polluted seasons. The strong nitrate acid production converts efficiently to nitrate particles due to high RH and ammonium-rich conditions during photochemical polluted seasons. This study highlights the efficient radical chemistry maintains the atmospheric oxidation capacity in Chinese megacities, which results in secondary pollutions characterized by ozone and fine particles.

As chinese aerospace industry developing rapidly, a great mass of spacecraft has been lunched into space. As these crafts far away from human's reach, we can hardly predict the failure state of these crafts but by analyzing temperature data transferred with their remote sensing information. In this paper, a failure prediction method is put forward on basis of Time Series Model and the temperature data of the spacecraft load. First, the load's real-time temperature data are tested by White Noise Analysis to analyze the validity of the model. Then the Stationarity Analysis and Differential Processing on the data are performed to obtain a smooth time series. And then, the parameter of ARIMA model can be determined according to the time series. At last, future load's temperature can be predicted by the model, according to which we can predict spacecraft load's failure state and by comparing it with the normal data. At the end of this paper, a remote sensing camera's real-time temperature data are used as an example to verifying this method. After comparing to the real situation of the load, the failure prediction method based on Time Series Model proposed in this paper is proved to be feasible.

From a global perspective, karst geological disaster has great influence on the tunnel construction. Once it is not handled properly, the karst problems in the tunnel area will cause great disaster, such as water inrush, mud gushing and collapse, etc. These karst disasters seriously affect the construction progress of the tunnel, resulting in equipment damage, casualties, and so on. The construction of Yichang–Wanzhou (YW) railway tunnel has created a miracle in the field of Chinese tunneling. The geology of tunnel area is quite complex, the karst disaster is remarkable, and the engineering construction is extremely difficult. In this paper, the karst characteristics, unfavorable geological disasters, and treatment methods of YW railway tunnel were analyzed systematically. The YW railway tunnel and Zhengzhou–Wanzhou (ZW) railway tunnel are both located in the Qinling-Daba (QB) mountainous area, and the regional geological conditions of them are very similar. Therefore, the research in this paper can be extended to the QB mountainous area, thus providing a reference for the construction of ZW railway tunnel. The investigation can also provide reference for the similar engineering.

Hydroxyl (OH) and peroxy radicals (HO2, RO2) were measured in the Pearl River Delta which is one of the most polluted areas in China, in autumn 2014. The radical observations were complemented by measurements of OH reactivity (inverse OH lifetime) and a comprehensive set of trace gases including CO, NOx and VOCs. OH reactivity was in the range between 15 s−1 and 80 s−1, of which about 50 % was unexplained by the measured OH reactants. In the three weeks of the campaign, maximum median radical concentrations were 4.5 × 106 cm−3 for OH at noon, and 3 × 108 cm−3 and 2.0 × 108 cm−3 for HO2 and RO2, respectively, in the early afternoon. The completeness of the daytime radical measurements made it possible to carry out experimental budget analyses for all radicals (OH, HO2, and RO2) and their sum (ROx). The maximum loss rates for OH, HO2, and RO2 reached values between 10 ppbv/h and 15 ppbv/h during daytime. The largest fraction of this can be attributed to radical interconveresio reactions while the real loss rate of ROx remained below 3 ppbv/h. Within experimental uncertainties, the destruction rates of HO2 and the sum of OH, HO2, and RO2 are balanced by their respective production rates. In case of RO2, the budget can only be closed when the missing OH reactivity is attributed to unmeasured VOCs. Thus, the existence of unmeasured VOCs is directly confirmed by RO2 measurements. Although the closure of the RO2 budget is greatly improved by the additional unmeasured VOCs, a significant imbalance in the afternoon remains indicating a missing RO2 sink. In case of OH, the destruction in the morning is compensated by the quantified OH sources from photolysis (HONO, O3), ozonolysis of alkenes and OH recycling (HO2 + NO). In the afternoon, however, the OH budget indicates a missing OH source of (4–6) ppbv/h. The diurnal variation of the missing OH source shows a similar pattern as that of the missing RO2 sink so that both largely compensate each other in the ROx budget. These observations suggest the existence of a chemical mechanism that converts RO2 to OH without the involvement of NO. The photochemical net ozone production rate calculated from the reaction of HO2 and RO2 with NO yields a daily integrated amount of 102 ppbv ozone with daily integrated ROx primary sources being 22 ppbv in this campaign. This value can be attributed to the oxidation of measured (18 %) and unmeasured (60 %) hydrocarbons, formaldehyde (14 %) and CO (8 %). An even larger integrated net ozone production of 140 ppbv would be calculated from the oxidation rate of VOCs with OH, if HO2 and all RO2 radicals would react with NO. However, the unknown RO2 loss (evident in the RO2 budget) causes 30 % less ozone production than would be expected from the VOC oxidation rate.

Saturable reactor used in UHVDC converter valve withstands periodic pulsed power loss, which will generate periodic pulsed electrical stress and pulsed thermal stress inside the epoxy resin insulation. The aging and life characteristics of epoxy resin insulation material under this condition are not clear yet. The operating conditions and insulation problems of saturable reactor are described in this article. Aiming at the electric and thermal aging factors, the pulsed electric aging experiment platform and the pulsed thermal effect experimental platform were designed respectively, and preliminary study on the life and aging characteristics of epoxy resin specimens were carried out. The results show that under the repeated action of the pulsed voltage, the lifetime of epoxy resin decreases with the increase of the voltage amplitude according to the inverse power law. Through magnified observation, we found that as the aging time increases, the surface roughness of the epoxy resin sample increases, and lots of pits appeared on surface. The repeated impact of pulsed heat has little effect on the surface electrical characteristics of the epoxy resin sample, but as the number of thermal shock increases, the electrical strength of the epoxy resin surface decreases.

To clarify the aerosol hygroscopic growth and optical properties of the Pearl River Delta (PRD) region, integrated observations were conducted in Heshan City of Guangdong Province from October 19 to November 17, 2014. The concentrations and chemical compositions of PM2.5, aerosol optical properties and meteorological parameters were measured. The mean value of PM2.5 increased from less than 35 (excellent) to 35-75 μg/m3 (good) and then to greater than 75 μg/m3 (pollution), corresponding to mean PM2.5 values of 24.9, 51.2, and 93.3 μg/m3, respectively. The aerosol scattering hygroscopic growth factor (f(RH = 80%)) values were 2.0, 2.12, and 2.18 for the excellent, good, and pollution levels, respectively. The atmospheric extinction coefficient (σext) and the absorption coefficient of aerosols (σap) increased, and the single scattering albedo (SSA) decreased from the excellent to the pollution levels. For different air mass sources, under excellent and good levels, the land air mass from northern Heshan had lower f(RH) and σsp values. In addition, the mixed aerosol from the sea and coastal cities had lower f(RH) and showed that the local sources of coastal cities have higher scattering characteristics in pollution periods.

Based on detailed data on 102 volatile organic compounds (VOCs) measured continuously from 2016.10.9 to 2016.11.17 in Wuhan, the VOC characteristics, secondary organic aerosol (SOA) characteristics, SOA formation potential (SOAP), potential source regions, sources and contributions during different haze episodes were analyzed. The total VOC (TVOC) concentrations on clear days (visibility10 km), slight haze days (visibility of 5-10 km), and severe haze days (visibility5 km) were 34.87 ± 14.89 ppbv, 45.06 ± 26.69 ppbv, and 49.55 ± 24.82 ppbv, respectively. The SOAP on haze days (447.04 ± 253.85 ppbv) was significantly higher than that on clear days (300.62 ± 138.48 ppbv), and aromatics were the dominant contributors to SOA formation under different visibility conditions, accounting for approximately 97% of the total SOAP. The ratio of ethylbenzene to m/p-xylene (E/X) indicated that atmospheric photochemical reactions were slightly stronger on haze days. The ratio of toluene to benzene (T/B) indicated that vehicle exhaust had significant effects on VOCs, but no significant changes occurred during different haze episodes. The ratio of benzene, toluene, ethylbenzene and xylenes (BTEX) to CO indicated that VOCs from solvent usage in painting/coating and industrial emissions increased with increasing haze pollution. Based on backward trajectories and the potential source contribution function (PSCF), short-distance transport was the main source influencing VOC pollution, especially transport from the southwest. Seven sources were identified by positive matrix factorization (PMF): industrial sources, vehicular exhaust, solvent usage in painting/coating, fuel evaporation, liquefied petroleum gas (LPG) usage, biogenic sources and biomass burning. Moreover, solvent usage in painting/coating, vehicle exhaust and LPG usage were the most important sources that significantly aggravated VOC pollution during haze events. The results can provide references for local governments developing control strategies of VOCs during haze pollution events.

To satisfy the demand of mobile computing and low-power application scenes, we propose a general reconfigurable embedded system design of convolution neural networks (CNN) based on FPGA and soft-core CPU. The basic computing modules are located in the hardware circuits, including convolution, pooling and active layers. Several controlling logic and serial data processing units are executed in the soft-core CPU. Based on the cooperation and interaction between hardware and software, the system is able to accomplish image identification and other CNN works with high speed and low power. As a case study to demonstrate the system's performance and validity, experiments with CNN project are implemented on an Altera Cyclone-IV FPGA board. Our system achieves a peak performance of 59.52GOPS under 120MHz working frequency, with the power of 1.35 W, achieving the power efficiency of 44.1GOPS/W.

With the fast development of very large scale integrated circuits (VLSI) lithography, hotspot detection is playing a crucial role in semiconductor design process. Nowadays pattern matching and machine learning achieve satisfactory performance, but because of the extreme scaling of transistor feature node and continue growing of layout pattern complexity, these traditional approaches may be ineligible for the tough task. In this paper, we introduce a hotspot detection method based on carefully designed deep learning network. At the same time, carefully analyzing the functionalities of different network layer types, we argue that pooling layer isn’t necessary for hotspot detection and can be replaced for better performance. On the other hand, since hotspot patterns are always in the minority in VLSI mask design, we apply folding, rotating and mirror-flipping for data augmentation of hotspot clips for seven times offline before training. The modified deep neural network can achieve comparable performance on the ICCAD 2012 contest benchmark.

Severe and persistent haze pollution involving fine particulate matter (PM2.5) concentrations reaching unprecedentedly high levels across many cities in China poses a serious threat to human health. Although mandatory temporary cessation of most urban and surrounding emission sources is an effective, but costly, short-term measure to abate air pollution, development of long-term crisis response measures remains a challenge, especially for curbing severe urban haze events on a regular basis. Here we introduce and evaluate a novel precision air pollution control approach (PAPCA) to mitigate severe urban haze events. The approach involves combining predictions of high PM2.5 concentrations, with a hybrid trajectory-receptor model and a comprehensive 3-D atmospheric model, to pinpoint the origins of emissions leading to such events and to optimize emission controls. Results of the PAPCA application to five severe haze episodes in major urban areas in China suggest that this strategy has the potential to significantly mitigate severe urban haze by decreasing PM2.5 peak concentrations by more than 60% from above 300 μg m−3 to below 100 μg m−3, while requiring ~30% to 70% less emission controls as compared to complete emission reductions. The PAPCA strategy has the potential to tackle effectively severe urban haze pollution events with economic efficiency.

To investigate the atmospheric oxidizing capacity in certain polluted isoprene-rich environments, such as the forests surrounding megacities. Here we present online observations of isoprene and its first-stage oxidation products methyl vinyl ketone (MVK) and methacrolein (MACR) in summer 2016 at a remote, high-altitude mountain forest site (1690 m a.s.l.) to the north of the air-polluted Pearl River Delta (PRD) region in southern China. The observed isoprene level was found to be significantly lower in comparison with other forest sites either in China or around the world, although the sampling site was surrounded with subtropical evergreen broad-leaved trees which are strong isoprene emitters. Also, high (MVK+MACR)/isoprene ratio was observed. Based on the observations, we hypothesized that the lower isoprene levels in the study forest might be attributable to a strong atmospheric oxidative capacity in relation to the elevated regional complex air pollution. High daytime OH and nighttime NO3 radical concentrations estimated by using a photochemical box model incorporating Master Chemical Mechanism (PBM-MCM), as well as calculated short atmospheric reaction times of isoprene and long photochemical age, indicated that the isoprene was rapidly and fully oxidized at this aged atmospheric environment, which confirmed our hypothesis. The study suggests that the complex air pollution in the PRD region has significantly elevated the background atmospheric oxidative capacity of the adjacent forests, and most likely does would probably affect the regional air quality and ecological environment in the long term. The feedback of forest ecosystems to the increasing atmospheric oxidation capacity warrants further studies.

The first wintertime in-situ measurements of hydroxyl (OH), hydroperoxy (HO2) and organic peroxy (RO2) radicals (ROx = OH + HO2 + RO2) in combination with observations of total reactivity of OH radicals, kOH in Beijing are presented. The field campaign “Beijing winter finE particle STudy – Oxidation, Nucleation and light Extinctions” (BEST-ONE) was conducted at the suburban site Huairou near Beijing from January to March 2016. It aimed to understand oxidative capacity during wintertime and to elucidate the secondary pollutants formation mechanism in the North China Plain (NCP). OH radical concentrations at noontime ranged from 2.4 × 106 cm−3 in severely polluted air (kOH ~ 27 s−1) to 3.6 × 106 cm−3 in relatively clean air (kOH ~ 5 s−1). These values are nearly two-fold larger than OH concentrations observed in previous winter campaign in Birmingham, Tokyo, and New York City. During this campaign, the total primary production rate of ROx radicals was dominated by the photolysis of nitrous acid accounting for 46 % of the identified primary production pathways for ROx radicals. Other important radical sources were alkene ozonolysis (28 %) and photolysis of oxygenated organic compounds (24 %). A box model was used to simulate the OH, HO2 and RO2 concentrations based on the observations of their long-lived precursors. The model was capable of reproducing the observed diurnal variation of the OH and peroxy radicals during clean days with a factor of 1.5. However, it largely underestimated HO2 and RO2 concentrations by factors up to 5 during pollution episodes. The HO2 and RO2 observed-to-modeled ratios increased with increasing NO concentrations, indicating a deficit in our understanding of the gas-phase chemistry in the high NOx regime. The OH concentrations observed in the presence of large OH reactivities indicate that atmospheric trace gas oxidation by photochemical processes can be highly effective even during wintertime, thereby facilitating the vigorous formation of secondary pollutants.

Daily PM2.5 samples were collected at an urban site in Beijing during four one-month periods in 2009-2010, with each period in a different season. Samples were subject to chemical analysis for various chemical components including major water-soluble ions, organic carbon (OC) and water-soluble organic carbon (WSOC), element carbon (EC), trace elements, anhydrosugar levoglucosan (LG), and mannosan (MN). Three sets of source profiles of PM2.5 were first identified through positive matrix factorization (PMF) analysis using single or combined biomass tracers - non-sea salt potassium (nss-K(+)), LG, and a combination of nss-K(+) and LG. The six major source factors of PM2.5 included secondary inorganic aerosol, industrial pollution, soil dust, biomass burning, traffic emission, and coal burning, which were estimated to contribute 31±37%, 39±28%, 14±14%, 7±7%, 5±6%, and 4±8%, respectively, to PM2.5 mass if using the nss-K(+) source profiles, 22±19%, 29±17%, 20±20%, 13±13%, 12±10%, and 4±6%, respectively, if using the LG source profiles, and 21±17%, 31±18%, 19±19%, 11±12%, 14±11%, and 4±6%, respectively, if using the combined nss-K(+) and LG source profiles. The uncertainties in the estimation of biomass burning contributions to WSOC due to the different choices of biomass burning tracers were around 3% annually and up to 24% seasonally in terms of absolute percentage contributions, or on a factor of 1.7 annually and up to a factor of 3.3 seasonally in terms of the actual concentrations. The uncertainty from the major source (e.g. industrial pollution) was on a factor of 1.9 annually and up to a factor of 2.5 seasonally in the estimated WSOC concentrations.

A new method has been developed to retrieve aerosol optical depth (AOD) from sunshine duration (SSD). Retrieved AODs from SSD at the six stations in northern China in 2003–2005 agree reasonably well with AODs retrieved from Moderate Resolution Imaging Spectroradiometer observations near the six stations. Values and trends in AOD retrieved from SSD in Beijing and Tianjin in the period 1961–2005 also agree with those retrieved from solar radiation and visibility. These agreements allow the retrieval of credible upper and lower limits for anthropogenic AODs from SSD at the six stations during 1961–2005. The trends in anthropogenic AODs are approximately a factor of 3 to 5 lower than the trends in emissions of gas-phase precursors of aerosols in 1973–2005, implying a significant sublinear relationship between the level of aerosols and emissions of their gas phase precursors. This finding has important implications for formulating a control strategy for PM2.5 or haze pollution in northern China.

Trends in precipitation are critical to water resources. Considerable uncertainty remains concerning the trends of regional precipitation in response to global warming and their controlling mechanisms. Here, we use an interannual difference method to derive trends of regional precipitation from GPCP (Global Precipitation Climatology Project) data and MERRA (Modern- Era Retrospective Analysis for Research and Applications) reanalysis in the near-global domain of 60°S–60°N during a major global warming period of 1979–2013. We find that trends of regional annual precipitation are primarily driven by changes in the top 30% heavy precipitation events, which in turn are controlled by changes in precipitable water in response to global warming, i.e., by thermodynamic processes. Significant drying trends are found in most parts of the U.S. and eastern Canada, the Middle East, and eastern South America, while significant increases in precipitation occur in northern Australia, southern Africa, western India and western China. In addition, as the climate warms there are extensive enhancements and expansions of the three major tropical precipitation centers–the Maritime Continent, Central America, and tropical Africa–leading to the observed widening of Hadley cells and a significant strengthening of the global hydrological cycle.

The north and east Pearl River Delta (PRD) is usually a clean, upwind area in autumn. Serious ozone pollution there in mid-late October 2008 was first discovered and then analyzed. Trajectory analysis, process analysis, ozone source apportionment technology, and sensitivity analysis were used to study this episode. Under the influence of a weak south wind, the precursors emitted in Guangzhou and Foshan were transported to the north and northeast PRD and formed ozone there, which resulted in high ozone concentration (>100 ppb). As the wind direction later transited to northerly, the precursors in the northeast PRD that originated from the central and west PRD were transported to the south, and caused severe ozone pollution in the southeast PRD. The ozone contributed by chemical processes reached >20 ppb/h in Jinguowan. More than 40 ppb ozone was contributed by the precursor emission in the central and west PRD during the episode. The ozone concentration was highly sensitive to the precursor emission in the PRD region in the high-ozone situations. This episode showed the complexity of regional pollution in the PRD. When the PRD is controlled by a low air pressure system and then cold air moves from northern China to the south, the risk of ozone pollution in the north and southeast PRD increases.

Based on a bounded approximate version of LU decomposition, we calculate the topological stable rank of \({{\mathcal {A}}}_{{\mathcal {N}}}\), which is a noncommutative version of the disc algebra. In addition, a general characterization of the maximal two-sided ideals of \({{\mathcal {A}}}_{{\mathcal {N}}}\) will be obtained.

In recent years, fine particulate matter (PM) pollution and visibility degradation have become severe air quality issues in China. In this study, PM 2.5 pollution over the Pearl River Delta (PRD) region during January, April, August, and November 2009 was simulated using the Community Multiscale Air Quality (CMAQ) model. An in-depth diagnostic analysis, focused on November 2009, was also conducted to reveal the patterns of sulfate and nitrate distribution, and to identify the main factors that influence the formation of sulfate and nitrate under typical meteorological conditions. The CMAQ model reasonably reproduced the observed concentrations, but showed better performance for January and November than it did for April and August, for which there was light-moderate underestimation of SO 2 , NO x , O 3 , PM 10 , and PM 2.5 concentrations, and slight overestimation of daily 8-h maximum concentrations of O 3 . Utilizing a sulfate tracking technique, it was found that on nearly 20 days in November 2009, characterized by northeasterly winds, cross-boundary transport contributed to >75% of the total sulfate budget, while local gas phase oxidation and primary emissions averaged 10% and 8%, respectively. Aqueous sulfate typically contributed less than 1% of the total sulfate budget, except when the winds were directed from the sea and high humidity favored aqueous oxidation, and the percentage contribution reached up to 46%. NH 3 was generally sufficient to fully neutralize H 2 SO 4 ; however, the formation of nitrate over the PRD was limited by the availability of NH 3 .

Significant increases of heavy precipitation and decreases of light precipitation have been reported over widespread regions of the globe. Global warming and effects of anthropogenic aerosols have both been proposed as possible causes of these changes. We examine data from urban and rural meteorological stations in eastern China (1955–2011) and compare them with Global Precipitation Climatology Project (GPCP) data (1979–2007) and reanalysis data in various latitude zones to study changes in precipitation extremes. Significant decreases in light precipitation and increases in heavy precipitation are found at both rural and urban stations, as well as low latitudes over the ocean, while total precipitation shows little change. Characteristics of these changes and changes in the equatorial zone and other latitudes suggest that global warming rather than aerosol effects is the primary cause of the changes. In eastern China, increases of annual total dry days (28 days) and ≥10 consecutive dry days (36%) are due to the decrease in light precipitation days, thereby establishing a causal link among global warming, changes in precipitation extremes, and higher meteorological risk of floods and droughts. Further, results derived from the GPCP data and reanalysis data suggest that the causal link exists over widespread regions of the globe.

Size-resolved aerosol samples were collected by MOUDI in four seasons in 2007 in Beijing. The PM 10 and PM 1.8 mass concentrations were 166.0 ± 120.5 and 91.6 ± 69.7 μg/m 3 , respectively, throughout the measurement, with seasonal variation: nearly two times higher in autumn than in summer and spring. Serious fine particle pollution occurred in winter with the PM 1.8 /PM 10 ratio of 0.63, which was higher than other seasons. The size distribution of PM showed obvious seasonal and diurnal variation, with a smaller fine mode peak in spring and in the daytime. OM (organic matter = 1.6 × OC (organic carbon)) and SIA (secondary inorganic aerosol) were major components of fine particles, while OM, SIA and Ca 2 + were major components in coarse particles. Moreover, secondary components, mainly SOA (secondary organic aerosol) and SIA, accounted for 46%–96% of each size bin in fine particles, which meant that secondary pollution existed all year. Sulfates and nitrates, primarily in the form of (NH 4 ) 2 SO 4 , NH 4 NO 3 , CaSO 4 , Na 2 SO 4 and K 2 SO 4 , calculated by the model ISORROPIA II, were major components of the solid phase in fine particles. The PM concentration and size distribution were similar in the four seasons on non-haze days, while large differences occurred on haze days, which indicated seasonal variation of PM concentration and size distribution were dominated by haze days. The SIA concentrations and fractions of nearly all size bins were higher on haze days than on non-haze days, which was attributed to heterogeneous aqueous reactions on haze days in the four seasons.

The idea of single particle aerosol mass spectrometry was first proposed in the 1970s and then developed quickly in recent two decades. Because it can simultaneously provide much information including particle size distribution, composition of multiple chemical species and mixing state for each single particle with high-time resolution, single particle aerosol mass spectrometry has been widely applied in the area of environmental monitoring and fine particulate matter research. This review aims to (1) provide an introduction of the development history and progress of single particle aerosol time-of-flight mass spectrometry, (2) summarize its principle, methods for data analysis, output of results and its applications in environmental measurement and research using two major commercialized instruments (ATOFMS and SPAMS), and (3) provide suggestions for future research.

A field experiment from 18 August to 8 September 2006 in Beijing, China, was carried out. A hazy day was defined as visibility

The Pearl River Delta (PRD) of China, which has a population of more than 58 million people, is one of the largest agglomerations of cities in the world and had severe PM 2.5 pollution at the beginning of this century. Due to the implementation of strong pollution control in recent decades, PM 2.5 in the PRD has continuously decreased to relatively lower levels in China. To comprehensively understand the current PM 2.5 sources in the PRD to support future air pollution control strategies in similar regions, we performed regional-scale PM 2.5 field observations coupled with a state-of-the-art source apportionment model at six sites in four seasons in 2015. The regional annual average PM 2.5 concentration based on the 4-month sampling was determined to be 37 µg m−3 , which is still more than 3 times the WHO standard, with organic matter (36.9 %) and SO 4 2 - (23.6 %) as the most abundant species. A novel multilinear engine (ME-2) model was first applied to a comprehensive PM 2.5 chemical dataset to perform source apportionment with predetermined constraints, producing more environmentally meaningful results compared to those obtained using traditional positive matrix factorization (PMF) modeling. The regional annual average PM 2.5 source structure in the PRD was retrieved to be secondary sulfate (21 %), vehicle emissions (14 %), industrial emissions (13 %), secondary nitrate (11 %), biomass burning (11 %), secondary organic aerosol (SOA, 7 %), coal burning (6 %), fugitive dust (5 %), ship emissions (3 %) and aged sea salt (2 %). Analyzing the spatial distribution of PM 2.5 sources under different weather conditions clearly identified the central PRD area as the key emission area for SO2 , NOx , coal burning, biomass burning, industrial emissions and vehicle emissions. It was further estimated that under the polluted northerly air flow in winter, local emissions in the central PRD area accounted for approximately 45 % of the total PM 2.5 , with secondary nitrate and biomass burning being most abundant; in contrast, the regional transport from outside the PRD accounted for more than half of PM 2.5 , with secondary sulfate representing the most abundant transported species.

We present the in-situ measurements in Chengdu, a major city in south west of China, in September 2016. The concentrations of ozone and its precursor were measured at four sites. Although the campaign was conducted in early autumn, up to 100 ppbv (parts per billion by volume) daily maximum ozone was often observed at all sites. The observed ozone concentrations showed good agreement at all sites, which implied that ozone pollution is a regional issue in Chengdu. To better understand the ozone formation in Chengdu, an observation based model is used in this study to calculate the RO

Nocturnal reactive nitrogen compounds are important for understanding regional air pollution. Here we present the measurements of dinitrogen pentoxide (N2O5) associated with nitryl chloride (ClNO2) and particulate nitrate (pNO3−) in a suburban site of Beijing in the summer of 2016. High levels of N2O5 and ClNO2 were observed in the outflow of the urban Beijing air masses, with 1-min average maxima of 937 pptv and 2.9 ppbv, respectively. The N2O5 uptake coefficients, γ, and ClNO2 yield, f, were experimentally determined from the observed parameters. The N2O5 uptake coefficient ranged from 0.012 to 0.055, with an average of 0.034 ± 0.018, which is in the upper range of previous field studies reported in North America and Europe but is a moderate value in the North China Plain (NCP), which reflects efficient N2O5 heterogeneous processes in Beijing. The ClNO2 yield exhibited high variability, with a range of 0.50 to unity and an average of 0.73 ± 0.25. The nighttime nitrate radical (NO3) was calculated assuming that the thermal equilibrium between NO3 and N2O5 was maintained. In NO2-rich air masses, the oxidation of nocturnal biogenic volatile organic compounds (BVOCs) was dominated by NO3 rather than O2. The production rate of organic nitrates (ONs) via NO2+BVOCs was significant, with an average of 0.11 ± 0.09 ppbv h−1. We highlight the importance of NO2 oxidation of VOCs in the formation of ONs and subsequent secondary organic aerosols in summer in Beijing. The capacities of BVOCs oxidation and ONs formation are maximized and independent of NOx under a high NOx/BVOCs ratio condition (>10), which indicates that the initial reduction of the NOx emission cannot help reduce the nocturnal formation of ONs.

Large-scale datasets have successively proven their fundamental importance in several research fields, especially for early progress in some emerging topics. In this paper, we focus on the problem of visual speech recognition, also known as lipreading, which has received increasing interest in recent years. We present a naturally-distributed large-scale benchmark for lip reading in the wild, named LRW-1000, which contains 1,000 classes with 718,018 samples from more than 2,000 individual speakers. Each class corresponds to the syllables of a Mandarin word composed of one or several Chinese characters. To the best of our knowledge, it is currently the largest word-level lipreading dataset and also the only public large-scale Mandarin lipreading dataset. This dataset aims at covering a "natural" variability over different speech modes and imaging conditions to incorporate challenges encountered in practical applications. It has shown a large variation in this benchmark in several aspects, including the number of samples in each class, video resolution, lighting conditions, and speakers' attributes such as pose, age, gender, and make-up. Besides providing a detailed description of the dataset and its collection pipeline, we evaluate several typical popular lipreading methods and perform a thorough analysis of the results from several aspects. The results demonstrate the consistency and challenges of our dataset, which may open up some new promising directions for future work., Comment: IEEE FG 2019

An order of magnitude improvement in the signal-to-noise ratio (SNR) of a 1550 nm LiDAR receiver was achieved using a few-mode optical preamplifier as compared to a multi-mode avalanche photodiode (APD). €

This study was designed to evaluate the global scientific output of simulation research in "meteorology and atmospheric sciences" for the past 16 years and to assess the characteristics of the atmospheric simulation research patterns, tendencies and methods in the papers, from leading countries and institutes. Data were based on the online version of Science Citation Index, Web of Science from 1992 to 2007. Articles referring to atmospheric simulation were assessed by exponential regression fitting the trend of publication outputs with r 2 = 0.9996, distribution of source countries, source institutes, source titles, author keywords, and keywords plus, and the four most cited articles in these years. By synthetic analysis of the three kinds of keywords, it was concluded that atmospheric simulation research related to "ozone", "climate", "circulation", "transport", "parameterization" and "assimilation" will be foci of atmospheric simulation research in the 21 st century.

An on-chip non-center-feed MMI power splitter for mode-multiplexed signals is proposed and experimentally demonstrated for the first time.

The CMB (Chemical Mass Balance) 8.2 model released by the USEPA is a commonly used receptor model that can determine estimated source contributions and their uncertainties (called default uncertainty). In this study, we propose an improved CMB uncertainty for the modeled contributions (called EV-LS uncertainty) by adding the difference between the modeled and measured values for ambient species concentrations to the default CMB uncertainty, based on the effective variance least squares (EV-LS) solution. This correction reconciles the uncertainty estimates for EV and OLS regression. To verify the formula for the EV-LS CMB uncertainty, the same ambient datasets were analyzed using the equation we developed for EV-LS CMB uncertainty and a standard statistical package, SPSS 16.0. The same results were obtained by both ways indicate that the equation for EV-LS CMB uncertainty proposed here is acceptable. In addition, four ambient datasets were studies by CMB 8.2 and the source contributions as well as the associated uncertainties were obtained accordingly.

A heavy haze episode that occurred in Beijing from 20 September to 27 September, 2011 was observed to explore the secondary processes of the haze episode. During the haze episode, the relatively stable synoptic conditions and regional transport from polluted areas in the south and southwest of Beijing favored the formation of haze. Significant increases of PM2.5/PM10 ratio was observed during haze period, which implied that the haze was caused by fine particles. Additionally, the presence of secondary inorganic pollutants (SO42–, NO3– and NH4+) sharply increased during the haze episode, which indicated that secondary processes significantly strengthened the haze episode. The sulfur oxidation ratio (SOR) sharply increased from a non-haze episode with a highest value of 0.11 to a haze episode with a highest value of 0.62. Low correlations between SOR and O3 and the temperature were found, whereas a high correlation between SOR and RH was found during the haze episode, which implied that sulfate was mainly produced by the aqueous-phase oxidation of SO2 rather than the gas-phase conversion of SO2 to sulfate in haze episode in Beijing. Furthermore, a fine linear relationship between SOR and the surface area (dS) of particles smaller than 1 µm confirmed the heterogeneous processes of sulfate formation in haze episode. The nitrogen oxidation ratio (NOR) also sharply increased from a non-haze episode with a highest value of 0.03 to a haze episode with a highest value of 0.26, which indicated more intense secondary formation of nitrate in haze episode. Nitrate was found to be mainly produced by a homogenous reaction under ammonium-rich conditions. Higher RH in haze episode reduced the thermodynamic equilibrium constant Ke’, and favored the thermodynamic equilibrium reaction of HNO3(g) + NH3(g) ↔ NH4NO3(s, aq) to formed nitrate, which might help explain the enhanced homogenous production of nitrate in haze episode. In addition, a good empirical fit (R2 = 0.70) between NOR and dS was found, which indicated that the particle surface area significantly contributed to the intense homogeneous production of nitrate in haze episode.

Serious air pollution in China now has great influence and threat on air quality, visibility, and human health. Accurate identification and quantification of sources play an important role in establishing relative policies, laws and control measures. This study briefly introduces development history and characteristics of three main methods to apportion sources of particles (emission inventory, source- oriented model and receptor model). Based on data platform of PM2.5 and chemical components conducted in Atlanta, USA, this study summarizes characteristics of major source apportionment methods of source-oriented model and receptor model and their performance towards different sources (i.e. vehicle emission, coal combustion, biomass burning, dust and secondary sources), points out the differences of various methods and potential reasons and analyzes their weakness and strength in application, suggesting that developing ensemble method should be an important direction for future source apportionment research.

Over the past couple of decades, root piles as the new tool for addressing a number of tough problems have been gaining a continually increasing interest in tunnel, especially for complex geological conditions. Therefore, in order to promote the development and application of root piles in tunnel engineering, this paper systematically sorts out the research status and development prospect of root piles from the application in foundation underpinning to reinforcement of tunnel foundation. Firstly, the type and development process of root piles are discussed. Secondly, the reinforcement mechanism of the root piles in the tunnel base is refined and combed: the reinforcement mechanism analysis focuses on frictional resistance of soil around pile, soil among piles, and piles. Thirdly, the calculation method of reinforced tunnel foundation is studied from the bearing of vertical load, horizontal load and pile reinforcement design. And through the engineering case, the paper illustrates the reinforcement effect of the root pile in ensuring the stability of the tunnel and the concrete process of the root piles in the tunnel construction. Finally, the problem and development prospect of root piles are discussed, so as to provide new perspectives and fundamental data for the research on tunnel engineering.

In this paper, we introduce a real-time pressure measurement system. A soft material with gauge points is placed ahead of a micro camera, and the material's deformation reflects the pressure applied on it. The image processing circuit mainly consists of an image pre-processing module, a connected area labeled module and a centroid coordinate calculation module. Experiments are implemented to demonstrate the system's performance of pressure direction and magnitude measurement, which can get a real-time measurement with a speed of 25fps.

In China, a significant reduction in primary pollution has been observed due to the Clean Air Action since 2013, and ozone pollution has become increasingly prominent over the past years. Pearl River Delta (PRD) is one of the most successful regions concerning primary pollution control, while is suffering from severe ozone pollution during autumn. In this study, we present a field campaign in Shenzhen, a megacity in PRD, in October 2018 with measurements of ozone and photochemical precursors. These observational data are helpful to analyze the local ozone budget and its sensitivity to precursors with the help of an observation-based model (RACM2-LIM1). The observed ozone concentration was up to 121 ppbv during a photochemical episode from 1 to 8 October, when intensive ozone formation up to tens of ppbv/h was found. Ozone vertical measurement indicates the fast ozone production is happening throughout the planetary boundary layer (PBL), which is an important source of morning ozone increase resulting in ozone pollution. An explicit case study is performed to reveal the diurnal feature of instantaneous ozone production rate (P(Ox)) and accumulative P(Ox) based on the O3-NOx-VOC sensitivity, ROx radical primary production rate (P (ROx)), and LN/Q for three cases including ozone pollution and attainment periods. Results show that nitrogen oxides (NOx = NO + NO2) reduction have positive and negative impact on local ozone production from one pollution episode to the other, which indicates the complexity of O3-precursors sensitivity and difficulty to control ozone pollution in Shenzhen. Finally, comparison among measurements in other campaigns provides additional evidence on local ozone production sensitivity on NOx and anthropogenic volatile organic compounds (AVOCs) with respect to a temporal and spatial change. The NOx reduction in Shenzhen has led to higher ozone production from 2015 to 2018 given the nearly constant VOC. However, the ozone mitigation would be benefit from further NOx reduction in the conditions of 2018.