bluuebunny/crossref_metadata_2025 huggingface dataset:
Impacts of Three Gorges Dam on Regional Circulation: A Numerical Simulation
Authors: Li Yan , Wu Liguang , Chen Xianyan , Zhou Weican
Published: July 2019

The Three Gorges Dam (TGD) is the largest hydropower project in the world. The resulting Three Gorges Reservoir (TGR) extends 660 km along the waterway of the Yangtze River in surrounded by complicated terrain. The dam and its impounded reservoir has triggered large‐scale land use and land cover change, which can potentially impact the environment and climate significantly. In this study, the impact of the TGD on regional‐scale circulation is explored through high‐resolution simulation using the weather research and forecast model. It is found that the construction of the TGD has little influence on the near‐surface temperature in the TGR region even when extreme hot weather occurs in the region. The numerical experiments performed in this study indicate that the construction of the TGD can alter the atmospheric circulation on the regional scale when the weak southeasterly wind in the lower troposphere prevails in the region. Due to the blocking effects of the TGD and the expanding water surface area of the TGR, the low‐level southeasterly flow is turned into northeasterly and southeasterly flows before reaching the dam, leading to an anomalous cyclone over 112–115°E, 33–34°N, and an anomalous anticyclone over 110–112°E, 28–29°N. It is also found that the anomalous cyclone can evidently enhance precipitation locally under some special atmospheric conditions. This study suggests that the impact of the TGD can be amplified due to the complicated terrain in the surrounding areas of the TGD.
Amplified Urban Heat Islands during Heat Wave Periods
Authors: Jiang Shaojing , Lee Xuhui , Wang Jiankai , Wang Kaicun
Published: July 2019

Heat waves and urban heat islands (UHIs) may interact together, but the dependence of their interaction on background climate is unclear. Hourly meteorological observations in June to August from 2013 to 2015 collected in the megacities of Beijing (temperate semihumid monsoon climate), Shanghai (subtropical humid monsoon climate), and Guangzhou (marine subtropical monsoon climate) in China were used to study the interaction. At each megacity, eight rural stations and eight urban stations, respectively, were selected to study the UHI. Although under different background climates, UHIs in Beijing and Guangzhou shared a similar diurnal variability, that is, higher in the nighttime. However, the diurnal cycle is opposite for Shanghai if rural coastal stations were selected as rural reference stations. During heat wave periods, daytime (10:00–16:00) UHIs were intensified by 0.9 ± 0.13 (mean ± 1 standard deviation) °C in Shanghai, nighttime (22:00–4:00) UHIs were intensified by 0.9 ± 0.36 and 0.8 ± 0.20 °C in Beijing and Guangzhou, respectively. The surface solar radiation during the heat wave period was approximately 1.5 times to that under normal conditions in each city. The enhanced solar radiation during heat waves, which was absorbed by the urban canopy in the daytime and released at night, was closely related to nighttime UHIs in Beijing and Guangzhou and daytime UHIs in Shanghai. Additionally, changes in wind direction were observed in Shanghai under heat waves, that is, with more than 63% (wind direction) of the wind originating from neighboring hot cities in the southwest instead of the cool sea breeze from the southeast, which led to a significant increase in daytime UHIs during heat wave periods.
Unlocking a Treasure Trove for Subsurface Characterization
Authors: McMillan Timothy , Rau Gabriel
Published: July 2019

Earth and atmospheric tide signatures embedded in groundwater levels are a potential game changer in the monitoring of confined aquifers.
The Search for the Impact That Cratered Ancient Scotland
Authors: Redd Nola
Published: July 2019

Great Britain’s largest impact crater likely lies in the Scottish Highlands. Scientists dispute whether it’s to the west or the east.
A More Accurate Global River Map
Authors: Underwood Emily
Published: July 2019

A new map of global river systems is based on crowdsourcing and the latest topography data sets.
The Mystery of the Moon’s Missing Metals
Authors: Redd Nola
Published: July 2019

For decades, scientists have tried to figure out why the Moon has a thousand times less precious metals than Earth. Turns out the metals may not have been delivered after all.
Zombie Worms, Ploonets, and Other Things We’re Reading This Week
Authors:   AGU
Published: July 2019

What Earth and space science stories are Eos staffers recommending this week?
Variation of Radiation Belt Electron Flux During CME‐ and CIR‐Driven Geomagnetic Storms: Van Allen Probes Observations
Authors: Pandya Megha , Bhaskara Veenadhari , Ebihara Yusuke , Kanekal Shrikanth G. , Baker Daniel N.
Published: July 2019

Relativistic electron flux responses in the inner magnetosphere are investigated for 28 magnetic storms driven by corotating interaction region (CIR) and 27 magnetic storms driven by coronal mass ejection (CME), using data from the Relativistic Electron‐Proton Telescope instrument on board Van Allen Probes from October 2012 to May 2017. In this present study we analyze the role of CIRs and CMEs in electron dynamics by sorting the electron fluxes in terms of averaged solar wind parameters, L‐values, and energies. The major outcomes from our study are the following: (i) At L = 3 and E = 3.4 MeV, for >70% cases the electron flux remains stable, while at L = 5, for ~82% cases it changes with the geomagnetic conditions. (ii) At L = 5, ~53% of the CIR storms and 30% of the CME storms show electron flux increase. (iii) At a given L‐value, the tendency for the electron flux variation diminishes with the increasing energies for both categories of storms. (iv) In case of CIR‐driven storms, the electron flux changes are associated with changes in Vsw and Sym‐H. (v) At L ~ 3, CME storms show increased electron flux, while at L ~ 5, CIR storms are responsible for the electron flux enhancements. (vi) During CME‐ and CIR‐driven storms, distinct electron flux variations are observed at L = 3 and L = 5.
Partial Melting of Mixed Sediment‐Peridotite Mantle Source and Its Implications
Authors: Zhang Yanfei , Wang Chao , Zhu Lüyun , Jin Zhenmin , Li Wei
Published: July 2019

Subducted sediments play an important role in the transport of incompatible elements back into the Earth's mantle. In recent years, studies of volcanic rocks from Samoan (Jackson et al., 2007, https://doi.org/10.1038/nature06048), NE China (Wang, Chen, et al., 2017, https://doi.org/10.1016/j.epsl.2017.02.028), and Gaussberg, Antarctica (Murphy et al., 2002, https://doi.org/10.1093/petrology/43.6.981), have shown geochemical records of a sediment‐influenced mantle source from the deep Earth. However, experimental studies on the partial melting behavior of mixed sediment‐peridotite mantle beyond subarc depths are very rare. In this study, we conducted experiments to investigate the partial melting behavior of mixed sediment‐peridotite mantle at 4–15 GPa and 1200–1800 °C. The experimental solidi of mixed sediment‐peridotite and K‐feldspar‐peridotite systems (Mixes A and B) cross the hot mantle geotherm at depths of around the X discontinuity (seismic discontinuity, ~300‐km depth). The trace element compositions of the corresponding partial melts in Mix A showed similar characteristics to those of the Samoan basaltic lavas, potassic basalts from NE China, and Gaussberg lamproites. Therefore, the experimental results provide a possible explanation for the origin of some unusual mantle‐derived volcanic rocks that contain recycled sediment signatures and have very deep origins. At depths of ~300 km (X discontinuity), a mixed sediment‐peridotite source was heated by a hot‐upwelling mantle and produced enriched melt. The enriched melt may interact with the surrounding mantle before incorporated into the upwelling mantle plume and becoming involved in the origin of some volcanic rocks. The experiments also provide a possible link between the enriched‐mantle source in the deep mantle and the X discontinuity.
Impacts of Changjiang River Discharge and Kuroshio Intrusion on the Diatom and Dinoflagellate Blooms in the East China Sea
Authors: Zhou Zheng‐Xi , Yu Ren‐Cheng , Sun Chaojiao , Feng Ming , Zhou Ming‐Jiang
Published: July 2019

The coastal area adjacent to the Changjiang River estuary is a high‐risk region for harmful algal blooms. Both Changjiang River discharge and Kuroshio intrusion influence the hydrological conditions and nutrient composition in this area which could affect the onset of diatom and dinoflagellate blooms. However, current understandings on their roles in regulating different microalgal blooms are limited. In this study, changes in stratification, water masses, and the ratio of phosphorus to nitrogen were examined during the diatom and dinoflagellate blooms in 2005 using ship cruise data. The observations showed that both the diatom and dinoflagellate blooms occurred in the continental coastal water. By enhancing the pycnocline and phosphorus stress, the Changjiang diluted water plays an important role in affecting the diatom bloom. The dinoflagellate bloom is partly supported by the supply of phosphate transported by Kuroshio intrusion and upwelling. The results of this study will help elucidate the mechanisms of large‐scale harmful algal blooms in the coastal area adjacent to the Changjiang River estuary.
Initial Leader Properties During the Preliminary Breakdown Processes of Lightning Flashes and Their Associations With Initiation Positions
Authors: Zheng Dong , Shi Dongdong , Zhang Yang , Zhang Yijun , Lyu Weitao , Meng Qing
Published: July 2019

The properties of initial leaders (ILs) of 1,056 flashes in two thunderstorms in Guangzhou, China, are analyzed. The median values of IL properties are 11.1 ms for duration, 2.2 km for vertical distance, 2.7 km for 3‐D distance, 1.9 × 105 m/s for vertical displacement speed, 2.4 × 105 m/s for 3‐D displacement speed, 28° for angle between the IL's displacement direction and the vertical direction, 1.1 per ms for pulse rate, 179 m for vertical step length, and 224 m for 3‐D step length. All the IL properties follow lognormal distributions. Strong monotonic relationships of IL duration with speed and pulse rate and pulse rate with speed and step length are revealed. With increasing initiation altitude, IL duration and step length tend to increase, and IL speed and pulse rate tend to decrease. The ILs initiated at approximately the −20 °C isotherm are more vertically orientated on average than those initiated at lower or higher levels. The ILs initiated in the strong kinematic areas generally had a greater speed and pulse rate but smaller duration, distance, and step length relative to those initiated in the weak kinematic areas. The possible impacts of the charge distribution patterns and density on the IL properties in different types of thunderstorms or thunderstorm areas are discussed.
Global Modeling of Secondary Organic Aerosol With Organic Nucleation
Authors: Zhu Jialei , Penner Joyce E.
Published: July 2019

Organic nucleation has been identified as an important way to form secondary organic aerosol (SOA) and change the number concentration of aerosol and thus its climate effect. A global atmospheric chemistry model is developed to include a comprehensive organic nucleation scheme that includes heteromolecular nucleation of sulfuric acid and organics, neutral pure organic nucleation, and ion‐induced pure organic nucleation. Our model simulation shows reasonable agreement with the seasonal as well as spatial pattern of organic carbon concentration in America, while it fails to predict the seasonal pattern of organic carbon in Europe due to the lack of sharp increases in primary organic aerosol emissions in the winter. Including organic nucleation decreases the bias of the annual average particle number concentration at 54% of the available observation sites and increases the temporal correlation coefficients at 58% of the sites. Ion‐induced pure organic nucleation contributes the most to the total organic nucleation rate, which peaks around 400 hPa in the tropics. Heteromolecular nucleation of sulfuric acid and organics dominates the total organic nucleation rate in the summer and mostly occurs in the lower troposphere. The number concentration of particles formed from organic nucleation (newSOA) in the nucleation and Aitken modes is highest in the tropics, while accumulation mode newSOA is highest in the Northern Hemisphere due to growth as a result of the condensation of sulfate. Three sensitivity experiments suggest that more studies are needed to investigate the formation mechanism of newSOA, so that a more accurate simulation of the spatial and size distribution of newSOA can be developed.
Estimation of Soil Evaporation and Vegetation Transpiration Using Two Trapezoidal Models From MODIS Data
Authors: Jiang Yazhen , Tang Ronglin , Jiang Xiaoguang , Li Zhao‐Liang , Gao Caixia
Published: July 2019

Soil evaporation (ETs) and vegetation transpiration (ETv) are essential in evaporative demand analyses and agricultural applications. This study estimated ETs and ETv using two trapezoidal models, that is, the conventional trapezoidal model and the end‐member‐based soil and vegetation energy partitioning (ESVEP) model, at three AmeriFlux tower sites. First, the land surface temperature of a Moderate Resolution Imaging Spectroradiometer (MODIS) pixel was decomposed into soil and vegetation temperatures (Ts and Tv, respectively) which involve important information related to ETs and ETv and were compared with corresponding temperatures from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). Then ETs and ETv were parameterized, and the total evapotranspiration (ET) was validated with the eddy covariance system measurements after energy imbalance corrections via the residual energy and Bowen ratio methods. The results showed that the ESVEP model partitioned Ts, with a root‐mean‐square error (RMSE) of 1.56–2.70 K (4.98–10.16%), and Tv, with an RMSE of 2.54–2.80 K (9.73–11.11%), indicating a higher accuracy than that from the conventional trapezoidal model, where the RMSE was 2.26–3.64 K (7.31–13.40%) for Ts separation and 2.82–4.62 K (9.80–15.49%) for Tv separation. For the ET estimation, the ESVEP model still performed better. The estimation RMSE was 49.8–58.4 W/m2 (22.8–27.2%) for the ESVEP model and 72.0–89.5 W/m2 (29.8–41.1%) for the conventional trapezoidal model, compared to the RE corrected measurements; the RMSE was 42.6–53.3 W/m2 (24.4–28.1%) for the ESVEP model and 57.5–78.1 W/m2 (32.3–37.9%) for the conventional trapezoidal model, compared to the Bowen ratio corrected measurements.
Observational Constraints on the Formation of Cl2 From the Reactive Uptake of ClNO2 on Aerosols in the Polluted Marine Boundary Layer
Authors: Haskins Jessica D. , Lee Ben H. , Lopez‐Hilifiker Felipe D. , Peng Qiaoyun , Jaeglé Lyatt , Reeves J. Michael , Schroder Jason C. , Campuzano‐Jost Pedro , Fibiger Dorothy , McDuffie Erin E. , Jiménez José L. , Brown Steven S. , Thornton Joel A.
Published: July 2019

We use observations from the 2015 Wintertime Investigation of Transport, Emissions, and Reactivity (WINTER) aircraft campaign to constrain the proposed mechanism of Cl2 production from ClNO2 reaction in acidic particles. To reproduce Cl2 concentrations observed during WINTER with a chemical box model that includes ClNO2 reactive uptake to form Cl2, the model required the ClNO2 reaction probability, γ (ClNO2), to range from 6 × 10−6 to 7 × 10−5, with a mean value of 2.3 × 10−5 (±1.8 × 10−5). These field‐determined γ (ClNO2) are more than an order of magnitude lower than those determined in previous laboratory experiments on acidic surfaces, even when calculated particle pH is ≤2. We hypothesize this is because thick salt films in the laboratory enhanced the reactive uptake ClNO2 compared to that which would occur in submicron aerosol particles. Using the reacto‐diffusive length‐scale framework, we show that the field and laboratory observations can be reconciled if the net aqueous‐phase reaction rate constant for ClNO2 (aq) + Cl‐(aq) in acidic particles is on the order of 104 s−1. We show that wet particle diameter and particulate chloride mass together explain 90% of the observed variance in the box model‐derived γ (ClNO2), implying that the availability of chloride and particle volume limit the efficiency of the reaction. Despite a much lower conversion of ClNO2 into Cl2, this mechanism can still be responsible for the nocturnal formation of 10–20 pptv of Cl2 in polluted regions, yielding an atmospherically relevant concentration of Cl atoms the following morning.
Modeling Dust in East Asia by CESM and Sources of Biases
Authors: Wu Mingxuan , Liu Xiaohong , Yang Kang , Luo Tao , Wang Zhien , Wu Chenglai , Zhang Kai , Yu Hongbin , Darmenov Anton
Published: July 2019

East Asian dust has a significant impact on regional and global climate. In this study, we evaluate the spatial distributions and temporal variations of dust extinction profiles and dust optical depth (DOD) over East Asia simulated from the Community Earth System Model (CESM) with satellite retrievals from Luo, Wang, Ferrare, et al. (2015, https://doi.org/10.1029/2002JD002775), Luo, Wang, Zhang, et al. (2015, https://doi.org/10.1002/2014GL062111) (L15), Yu et al. (2015, https://doi.org/10.1016/j.rse.2014.12.010) (Y15), and Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) level 3 products. Both L15 and Y15 are based on CALIPSO products but use different algorithms to separate dust from nondust aerosols. We find high model biases of dust extinction in the upper troposphere over the Taklamakan desert, Gobi desert, and Tibetan Plateau, especially in the summer (June‐July‐August). CESM with dust emission scheme of Kok, Mahowald, et al. (2014, https://doi.org/10.5194/acp‐14‐13023‐2014) and Kok, Albani, et al. (2014, https://doi.org/10.5194/acp‐14‐13043‐2014) has the best agreement with dust extinction profiles and DOD from L15 in the Taklamakan desert and Tibetan Plateau. CESM with the default dust emission scheme of Zender, Bian, and Newman (2003, https://doi.org/10.1029/2002JD002775) underpredicts DOD in the Tibetan Plateau compared with observations from L15 due to the underestimation of local dust emission. Large uncertainties exist in observations from L15, Y15, and CALIPSO level 3 products and have significant impacts on the model evaluation of dust spatial distributions. We also assess dust surface concentrations and 10‐m wind speed with meteorological records from weather stations in the Taklamakan and Gobi deserts during dust events. CESM underestimates dust surface concentrations at most weather stations due to the inability of CESM to capture strong surface wind events.
Predictability of Stratospheric Sudden Warmings in the Beijing Climate Center Forecast System with Statistical Error Corrections
Authors: Rao Jian , Ren Rongcai , Chen Haishan , Liu Xiangwen , Yu Yueyue , Hu Jinggao , Zhou Yang
Published: July 2019

Previous studies have reported that the predictive limit of stratospheric sudden warming (SSW) events in the Beijing Climate Center forecast system (BCC_CSM) is shorter than 2 weeks. This study continues to analyze the general characteristics of this model in forecasting SSWs and carries out a trial of error corrections. The ratio of the ensemble members that forecast the zonal wind reversal with a 5‐day delay allowed (hit ratio) is higher for SSW events with a small decrease in the zonal mean zonal winds (moderate SSWs) than for events with a large decrease in the zonal mean zonal winds (radical SSWs) in hindcasts initialized around 1 (D‐7) and 2 (D‐14) weeks in advance. The underestimated cumulative eddy heat flux associated with weak wave activities accounts for the weaker‐than‐observed deceleration of westerlies. The preexisting extratropical wave patterns are satisfactorily forecast in D‐14 for most (9/12) cases, and the wave phase bias is reasonably small for those cases. After the climatology bias is deducted from the hindcasts, an increase in the hit ratio can be identified for moderate SSW events as the evolutions of zonal winds are improved. Following the error correction by remapping the zonal wind probability distribution function in the forecast system to the reanalysis, the SSW hit ratios increase in the D‐7 (43% to 57%) and/or D‐14 (11% to 21%) initializations. Based on the composite result, this error correction method robustly improves the hit ratio not only for both radical SSWs and moderate SSWs but also for both polar vortex split SSWs and polar vortex displacement SSWs. The best error correction method might propel the prediction limit of SSW events to around 2 weeks.
Thermotectonic History of the Kluane Ranges and Evolution of the Eastern Denali Fault Zone in Southwestern Yukon, Canada
Authors: McDermott Robert G. , Ault Alexis K. , Caine Jonathan Saul , Thomson Stuart N.
Published: July 2019

Exhumation and landscape evolution along strike‐slip fault systems reflect tectonic processes that accommodate and partition deformation in orogenic settings. We present 17 new apatite (U‐Th)/He (He), zircon He, apatite fission‐track (FT), and zircon FT dates from the eastern Denali fault zone (EDFZ) that bounds the Kluane Ranges in Yukon, Canada. The dates elucidate patterns of deformation along the EDFZ. Mean apatite He, apatite FT, zircon He, and zircon FT sample dates range within ~26–4, ~110–12, ~94–28, and ~137–83 Ma, respectively. A new zircon U‐Pb date of 113.9 ± 1.7 Ma (2σ) complements existing geochronology and aids in interpretation of low‐temperature thermochronometry data patterns. Samples ≤2 km southwest of the EDFZ trace yield the youngest thermochronometry dates. Multimethod thermochronometry, zircon He date‐effective U patterns, and thermal history modeling reveal rapid cooling ~95–75 Ma, slow cooling ~75–30 Ma, and renewed rapid cooling ~30 Ma to present. The magnitude of net surface uplift constrained by published paleobotanical data, exhumation, and total surface uplift from ~30 Ma to present are ~1, ~2–6, and ~1–7 km, respectively. Exhumation is highest closest to the EDFZ trace but substantially lower than reported for the central Denali fault zone. We infer exhumation and elevation changes associated with ~95–75 Ma terrane accretion and EDFZ activity, relief degradation from ~75–30 Ma, and ~30 Ma to present exhumation and surface uplift as a response to flat‐slab subduction and transpressional deformation. Integrated results reveal new constraints on landscape evolution within the Kluane Ranges directly tied to the EDFZ during the last ~100 Myr.
The efficient profiling of serum N-linked glycans by a highly porous 3D graphene composite
Authors: Niu Huan , Li Xin , Peng Jiaxi , Zhang Hongyan , Zhao Xingyun , Zhou Xiaoyu , Yu Dongping , Liu Xinyu , Wu Ren'an
Published: July 2019

In this work, an enrichment approach to profile N-linked glycans was developed by utilizing a highly porous 3D graphene composite fabricated from the graphene oxide nanosheets and the phenol-formaldehyde polymer via a KOH activation process.
Systems chemical analytics: introduction to the challenges of chemical complexity analysis
Authors: Schmitt-Kopplin Philippe , Hemmler Daniel , Moritz Franco , Gougeon Régis D. , Lucio Marianna , Meringer Markus , Müller Constanze , Harir Mourad , Hertkorn Norbert
Published: July 2019

We present concepts of complexity, and complex chemistry in systems subjected to biotic and abiotic transformations, and introduce analytical possibilities to disentangle chemical complexity into its elementary parts as a global integrated approach termed systems chemical analytics.
Multicompartment emulsion droplets for programmed release of hydrophobic cargoes
Authors: Chen Xiao-Wei , Ning Xue-Ying , Zou Yuan , Liu Xiao , Yang Xiao-Quan
Published: July 2019

Multi-compartmentalized microdroplets composed of a multiple subcompartment shell and single microscale host compartment core were prepared facilely for achieving programmed release of hydrophobic cargoes.
Hierarchically structured microchip for point-of-care immunoassays with dynamic detection ranges
Authors: Mou Lei , Dong Ruihua , Hu Binfeng , Li Zulan , Zhang Jiangjiang , Jiang Xingyu
Published: July 2019

We report a hierarchically structured microchip combined with an automated and portable device for dynamic multiplexed immunoassays. Our system can detect multiple biomarkers from pg mL−1to μg mL−1spanning a dynamic range of 10 orders of magnitude.
Eco-friendly porous iron(iii) oxide micromotors for efficient wastewater cleaning
Authors: Peng Xia , Zhu Hongli , Chen Huijun , Feng Xiaomiao , Liu Ruiqing , Huang Zhendong , Shen Qingming , Ma Yanwen , Wang Lianhui
Published: July 2019

Eco-friendly porous iron(iii) oxide micromotors obtained by calcining octahedral PB microcrystals are used for efficient adsorption of organic pollutants in water.
Electrodeposited Ni(OH)2-modified CuS core–shell-like hybrids as binder-free electrodes for high-performance supercapacitors
Authors: Naveenkumar P. , Kalaignan G. Paruthimal
Published: July 2019

In this work, binder-free electrodes of CuS@Ni(OH)2 were fabricated by hydrothermal and electrodeposition methods.
Ultrafast nano-structuring of superwetting Ti foam with robust antifouling and stability towards efficient oil-in-water emulsion separation
Authors: Yang Shuai , Yin Kai , Wu Junrui , Wu Zhipeng , Chu Dongkai , He Jun , Duan Ji-An
Published: July 2019

We report a simple, rapid method to prepare robust superwetting Ti foam for efficient separation of oil-in-water emulsions.
Organocatalytic synthesis of enantiopure spiro acenaphthyl-pyrrolizidine/pyrrolidines: justifying the regioselectivity based on a distortion/interaction model
Authors: Shahrestani Naeimeh , Khosravi Hormoz , Jadidi Khosrow , Notash Behrouz , Naderi Soheila
Published: July 2019

An efficient organocatalytic synthesis of chiral spiroacenaphthyl-pyrrolidines/pyrrolizidines with high regio- and diastereoselectivity (up to 99%) with exact specification of the absolute configuration is described for the first time.
(Z)-Tetrahydrothiophene and (Z)-tetrahydrothiopyran synthesis through nucleophilic substitution and intramolecular cycloaddition of alkynyl halides and EtOCS2K
Authors: Luo Xianglin , Li Yibiao , Chen Xiuwen , Song Zhiyan , Liang Junyi , Liao Chunshu , Zhu Zhongzhi , Chen Lu
Published: July 2019

This protocol provides a novel method for the synthesis of (Z)-tetrahydrothiophene derivatives through the formation of C–S bonds under transition-metal-free condition using thiyl radical intramolecular cycloaddition cascade strategy.
Highly nanocrystalline interconnected La0.5Ca0.5CoO3−δ as an efficient bi-functional electrocatalyst for zinc–air batteries with structural and morphological evidence for ZnO mitigation
Authors: Kanagaraj Inthumathi , Moni Prabu , Prakash A. S.
Published: July 2019

This work highlights the evidence of ZnO formation and its mitigation strategies to enhance the performance of Zn–air batteries.
Research on a physical activity tracking system based upon three‐axis accelerometer for patients with leg ulcers
Authors: Yan Rongguo , Zhao Weibing , Sun Qi
Published: July 2019

Venous leg ulcerations are a common problem, with high prevalence in the middle‐aged and elderly population, and more attention on research of their physical activities has been paid, as they have great effects on the blood circulation of the lower limb. With enough, appropriate training, the chronic venous ulcerations in the lower limb can be avoided and alleviated, and venous hypertension can be reduced effectively. The study deals with a physical activity tracking system for the patients based on a three‐axis accelerometer. The system uses a three‐axis accelerometer, a microcontroller, and a wireless Bluetooth module to form a data acquisition platform to acquire accelerations of the lower limb movement, and sends it to a smart mobile phone via the wireless Bluetooth module. The system takes advantages of the smart mobile phone to guide the chronic venous leg ulcers to do prescribed rehabilitation exercises for the lower limb muscles, perform acceleration data preprocessing, wavelet transform and reconstruction, denoising and feature extraction, obtain the results of the rehabilitation exercises, and then give reasonable evaluation and judgment. It is helpful to treat underlying venous reflux, create such an environment that allows skin to grow across an ulcer, and accelerate ulcer healing process consequently.
Power quality improvement of single phase weak grid interfaced hybrid solar PV and wind system using double fundamental signal extracter‐based control
Authors: Gupta Tripurari Nath , Murshid Shadab , Singh Bhim
Published: July 2019

In this study, a double fundamental signal extracter using third‐order signal integrator‐based control technique is used for the improvement of power quality of single phase grid interfaced with hybrid wind energy generation system (WEGS) and solar photovoltaic (PV) array under weak grid conditions. The control algorithm is proposed for the extraction of dual fundamental components of load current and to extract fundamental grid voltage for synchronisation to the grid. The main objective of the system is to establish secure, reliable and safe integration while mitigating several power quality issues such as total harmonic distortion (THD) of the grid current, DC current injection. The system operates in distribution static compensator mode in the absence of renewable energy sources and also, maintains the grid current THD as per the limit of the IEEE‐519 standard. For optimal power extraction from WEGS as well as the solar PV array, perturb and observe algorithm is used. The prototype developed in the laboratory is tested under different operating conditions such as variable wind speed, grid voltage sag/swell, variable solar insolation, and varying load conditions.
Synchronised measurements based transient security assessment of power systems using AdaBoost classifiers
Authors: Venkatesh Thirugnanasambandam , Jain Trapti
Published: July 2019

This study proposes an adaptive boosting (AdaBoost) algorithm for precise and accurate prediction of transient security assessment of power systems using synchronised measurements. The proposed approach (PRPA) also determines the generator coherent state as well as the synchronism status of each generating unit. The PRPA consists of three classifier models, in which classifier I determines the transient security status and classifier II is used to determine the generator coherency. Classifier III is a hybrid classifier, which determines the individual generator synchronism state for a given operating condition. This hybrid classifier consists of an array of parallel classifiers, where one classifier is assigned to each generating unit of the power system. For this assessment, the measured rotor angles of the generators are used as inputs to the proposed classifier models. In classification stage, several weak classifiers are combined in a linear manner to construct a strong classifier. The performance of the AdaBoost algorithm is further improved by a new weight updation strategy using fuzzy clustering thresholding technique. Simulation results obtained from IEEE 14‐bus, IEEE 30‐bus and Indian 246‐bus systems reveal that the PRPA can enhance the overall monitoring and assessment of power system using synchronised measurements.
Interpretation of frequency response analysis of power transformer based on evidence theory
Authors: Shamlou Alireza , Reza Feyzi Mohammad , Behjat Vahid
Published: July 2019

Power transformers are one of the key components of power systems. Therefore, they must be operated efficiently to obtain satisfactory system performance, since any distortion or failure in power transformer structures may cause drastic damages. In order to detect deficiencies in power transformers, various methods are utilised. Frequency response analysis (FRA) is one of the most well‐known methods used for fault detection in power transformers. However, the interpretation of FRA results is subjective, and depends primarily on the opinion of a human expert. In other words, there is no comprehensive, accepted and standardised method to interpret FRA results. Subsequently, fault detection based on FRA is prone to error. In this study, a new mathematical approach is used to interpret the frequency response of power transformers based on evidence theory method. This method is more accurate and less computationally burdensome compared to conventional methods. Simulations are implemented on an operating 125 MVA, 230/132/20 kV autotransformer using finite‐element method and the results are compared to the corresponding FRA results of the same autotransformer in order to evaluate the proposed method. The obtained results indicate the efficiency of the proposed method in detecting probable faults of transformer windings through analysing the FRA results.
Optimisation model and solution method of multi‐sources guide paths
Authors: Mao Feng , Huang Min , Zheng Jian , Qian Yuxiang
Published: July 2019

Guiding accessibility is a principal function of guide sign, which indicates whether the guide signs can guide people to their destinations successfully or not. The authors build an effective model to optimise the guiding accessibility of guide signs with a minimum economic cost. The authors’ work can benefit guide sign setting, and improve the efficiency of the traffic system. Firstly, the authors introduced the representation of the road network, then the accessibility and integrated optimisation of guiding paths are defined. Based on this, an integrated optimisation model is proposed with the optimisation of the guiding path length and the number of guide signs. Then combining with the genetic algorithm, the algorithm is designed to solve the mixed integer linear programming problem. Lastly, Guangzhou Higher Education Center is chosen as the test area. The integrated optimisation of the multiple guiding paths with the destination of Sun Yat‐sen University is realised using the proposed model. The experiment results show that the proposed model can realise the integrated optimisation of an unsuccessful guiding path with the minimum economic cost.
Some features of car‐following behaviour in the vicinity of signalised intersection and how to model them
Authors: Zhang Jian , Tang Tie‐qiao , Wang Tao
Published: July 2019

In the context of urban traffic increasing, the study of driving behaviour in the vicinity of signalised intersection is emerging. Driving behaviour on the signalised road is different from the one on the highway due to the influence of signal lights. In this study, the authors analyse the trajectory data of Lankershim Boulevard from the next generation simulation (NGSIM) database. The car‐following data are filtered to exclude the influences of lane changing. They analyse the driving data from both micro‐ and macro‐perspectives. The quantitative relationship between acceleration and other factors, as well as the distribution of headway, are analysed. It is found that the statistic features of headway are in a discrepancy between different signal data. A simulation testbed is constructed, and two calibrated traditional car‐following models are utilised to reproduce the driving behaviour at signalised intersections. The simulation results illustrate that the traditional models cannot be used to simulate traffic flow on the signalised road, i.e. they cannot describe the difference of headway under different signal states. Based on the data analyses, the authors propose a new car‐following model with the consideration of signal status. The simulation results of the new model are in better agreement with the actual data.
Optimal control problem of multi‐vehicle cooperative autonomous parking trajectory planning in a connected vehicle environment
Authors: Wu Bing , Qian Lijun , Lu Meiling , Qiu Duoyang , Liang Haiqin
Published: July 2019

The development of intelligent network and intelligent vehicle technology makes it possible for multi‐vehicle cooperative driving. In this study, the multi‐vehicle cooperative autonomous parking condition is addressed by establishing a vehicle kinematics model combined with dynamic constraints and endpoint and collision avoidance constraints. The autonomous parking trajectory planning problem is transformed into an optimal control problem. The shortest parking completion time is set as the optimal cost function, and the optimal control problem is discretised by using the Gauss pseudo‐spectral method. Then, the non‐linear programming problem is solved. Moreover, an initial guess generation strategy is proposed, and the iteration method is used to solve the problem by adding collision avoidance constraints to the collision situation of the vehicle to improve the convergence and robustness of the problem. The simulation model is built in MATLAB/Simulink to simulate multi‐vehicle cooperative autonomous parking under different working conditions. The simulation results show that the proposed method can solve the multi‐vehicle cooperative autonomous parking trajectory planning problem uniformly and effectively. Compared with the traditional pseudo‐spectral method, the proposed method has a faster convergence speed.
Silicon photonic spiral shape resonator applied to the optoelectronic oscillator
Authors: Do Phuong T. , Alonso‐Ramos Carlos , Le Roux Xavier , Vivien Laurent , Marris‐Morini Delphine , Crozat Paul , Ledoux‐Rak Isabelle , Cassan Eric , Journet Bernard
Published: July 2019

We present here the implementation of an optoelectronic oscillator (OEO) that leverages the optical comb produced by a silicon add‐drop ring resonator to directly convert signals from optical to microwave domain. The OEO comprises a CW laser, an intensity modulator, a silicon add‐drop ring, a photodetector, and radiofrequency amplifier. By using millimeter‐long silicon‐on insulator micro‐ring resonator, we generated an oscillation signal with a frequency determined by the free spectral range (FSR) of the ring. In this scheme, the sharp transmission peaks in the drop port of an add‐drop silicon resonator are used as the optical comb. The optimised ring has a length of 5.8 mm with a measured FSR of 112 pm, an extinction ratio of 20 dB and an optical quality factor of 2.2 × 105. The complete OEO loop yields a 14.12 GHz signal with a phase noise level of −100 dBc/Hz at an offset of 100 kHz from the carrier. This result shows that OEOs directly based on millimeters long silicon rings are a promising path for generating low‐noise microwave signals.
Temporal and frequency‐domain assessment of thermal and electrical ageing of mineral and vegetable oils
Authors: Chetibi Fouzia , Moulai Hocine , Idir Omar
Published: July 2019

This study focuses on the effect of accelerated thermal and electrical ageing on the dielectric properties of two vegetable oils (olive and soya oils) and a mineral oil which are thermally aged in sealed bottles at 110°C for durations up to 720 h and electrically submitted up to 2500 low‐energy discharges under DC voltage. The investigated properties are the real part of the complex relative permittivity, dissipation factor and conductivity in a large frequency range (20 Hz–10 MHz) using frequency domain spectroscopy. This study also discusses the discharge currents generated in these oils and their corresponding fast Fourier transforms followed by power spectral density analysis. The electrical discharges are applied to the oil samples in a plane–plane configuration electrodes and 2.5 mm gap under DC voltage. The frequency‐domain investigated descriptors are: maximum peak, mean value, rms value, peak factor, variance and standard deviation of magnitude spectrum, in addition to the resonance and bandwidth frequency of discharge currents. Furthermore, the spectrograms of these discharge currents are presented, illustrating how the frequency composition and the intensity of each frequency change with time.
Combining standard with optimised split‐step finite‐difference time‐domain methods for the study of graphene configurations
Authors: Amanatiadis Stamatios A. , Zygiridis Theodoros T. , Kantartzis Nikolaos V.
Published: July 2019

In this study, the authors propose a hybrid computational model for the reliable simulation of electromagnetic‐wave phenomena emerging in graphene structures, which incorporates two variations of an unconditionally‐stable finite‐difference time‐domain algorithm. The new approach features: (a) a dispersive model that relies on the auxiliary differential equation technique and takes into consideration the graphene's surface conductivity, and (b) a modified discretisation algorithm implementing error‐optimised spatial approximations, which is appropriate for graphene‐free mesh nodes. The resulting update equations are devoid of time‐step restrictions, thus formulating a suitable and useful computational framework for the investigation of contemporary graphene‐based problems, which commonly call for densely‐sampled grids and/or prolonged simulations. After theoretically assessing the fundamental features of the proposed algorithm, the propagation properties of surface waves on graphene are extracted numerically and compared with analytical estimations, so that computational validation is provided. In addition, a realistic surface‐wave coupler configuration is simulated and its main characteristics are extracted accurately, exemplifying the method's robustness on more complex setups.
Estimation of paper conductivity from short duration polarisation–depolarisation current for diagnosis of power transformer
Authors: Mishra Deepak , Haque Nasirul , Baral Arijit , Chakravorti Sivaji
Published: July 2019

The value of paper conductivity provides quantitative evaluation of transformer insulation health. However, proper identification of paper conductivity requires complete profile of polarisation–depolarisation current (PDC). PDC measurement being a time‐consuming offline process generally takes several hours to complete. Furthermore, magnitude of PDC becomes very low at larger value of time, which makes it sensitive to changes in environmental conditions and field noise. Hence, accuracy of paper conductivity identification can be ensured by conducting multiple measurements. This in‐turn prolongs shutdown time of equipment and become less advantageous to utilities. Here, a method is proposed which is capable of estimating paper conductivity using PDC data recorded for only 800 s. The proposed technique is tested on data collected from several real‐life in‐service transformers. In order to illustrate the accuracy of the proposed technique, paper conductivities (calculated from short duration PDC) were compared with those computed using PDC measured for 10,000 s.
Evaluation of strand‐to‐strand capacitance and dissipation factor in thermally aged enamelled coils for low‐voltage electrical machines
Authors: Madonna Vincenzo , Giangrande Paolo , Galea Michael
Published: July 2019

The dissipation factor (i.e. tanδ) and insulation capacitance (IC) measurements are conventional monitoring methods for assessing the aging level of insulation systems. These quantities provide an invaluable indication of the dielectric losses within the insulating materials. However, how these values are affected by the aging processes due to thermal stresses have until today never been investigated fully. Thus, this study exhibits the influence of thermal aging on tanδ and IC of windings for electrical machines (EMs). The work is performed for class 200, round enamelled magnet wire specimens. The study aims at improving the design process of EMs for short duty cycle applications; hence, its outcome might be included at the design stage for enhancing reliability and lifetime. Random wound coils are chosen in the performed study, because they are the most common winding arrangement for low‐voltage EMs, which are employed in a wide range of applications (e.g. from home appliances to aerospace motors). Based on the collected data, considerations regarding the impact of relative humidity on both the dissipation factor and IC are presented. Finally, the correlation between the partial discharge inception voltage and the diagnostic measurements is experimentally verified.
High‐speed data acquisition of the reader of the SAW RFID system
Authors: Chen Zhijun , Jia Hao , Chen Tao , Wang Xinchen , Guo Jiajia , Cai Pinggen
Published: July 2019

The measurement of the echo time delays and phases of the surface acoustic wave (SAW) tag by the corresponding reader should be more accurate with the increase of the coding capacity, and the design of the high‐speed data acquisition module (DAM) is the key factor for the improvement of the reader performance. Aiming at the large capacity SAW tag, which combines pulse time delay and phase coding, the radio‐frequency (RF) band‐pass sampling and digital quadrature demodulation scheme is utilised for the reader design. The design of the high‐speed DAM includes the analysis, calculation and determination of the sampling frequency, the sampling clock design with cascaded phase‐locked loop structure and the driver circuit design etc. Finally, the SAW RFID system is established, and the time delays and phases of the tag reflectors are tested. The measurement results show the effectiveness of the high‐speed DAM of the reader.
Design and preliminary verification of L‐band ground‐based SAR system for the vegetated area
Authors: Yang Wenyu , Tian Weiming , Mei Hongyan , Hu Cheng , Zeng Tao
Published: July 2019

Ground‐based synthetic aperture radar (GB‐SAR) is a novel system applied deformation monitoring of buildings, mountains, and mining slopes with the advantages of high‐resolution, large‐scale monitoring, and fast image acquisition image interval. Most of current GB‐SAR systems work in the high‐frequency band, without the ability of vegetation penetration. So here, a GB‐SAR system used for vegetated area is designed on the carrier frequency and other important parameters under the requirements for vegetation penetration, high‐resolution and large‐scale imaging. At last, the imaging ability and vegetation penetration ability of the designed GB‐SAR system are assessed and verified through simulations and experiments.
Massive star cluster formation and evolution in tidal dwarf galaxies
Authors: Fensch Jérémy , Duc Pierre-Alain , Boquien Médéric , Elmegreen Debra M. , Elmegreen Bruce G. , Bournaud Frédéric , Brinks Elias , de Grijs Richard , Lelli Federico , Renaud Florent , Weilbacher Peter M.
Published: July 2019

Context. The formation of globular clusters remains an open debate. Dwarf starburst galaxies are efficient at forming young massive clusters with similar masses as globular clusters and may hold the key to understanding their formation.

Aims. We study star cluster formation in a tidal debris, including the vicinity of three tidal dwarf galaxies, in a massive gas-dominated collisional ring around NGC 5291. These dwarfs have physical parameters that differ significantly from local starbursting dwarfs. They are gas rich, highly turbulent, their gas metallicity is already enriched up to half solar values, and they are expected to be free of dark matter. The aim is to study massive star cluster formation in this as yet unexplored type of environment.

Methods. We used imaging from the Hubble Space Telescope using broadband filters that cover the wavelength range from the near-ultraviolet to the near-infrared. We determined the masses and ages of the cluster candidates by using the spectral energy distribution-fitting code CIGALE. We considered age-extinction degeneracy effects on the estimation of the physical parameters.

Results. We find that the tidal dwarf galaxies in the ring of NGC 5291 are forming star clusters with an average efficiency of ∼40%, which is similar to blue compact dwarf galaxies. We also find massive star clusters for which the photometry suggests that they were formed at the very birth of the tidal dwarf galaxies. These clusters have survived for several hundred million years. Therefore our study shows that extended tidal dwarf galaxies and compact clusters may be formed simultaneously. In the specific case observed here, the young star clusters are not massive enough to survive for a Hubble time. However, it may be speculated that similar objects at higher redshift, with a higher star formation rate, might form some of the long-lived globular clusters.