bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of bismaleimide resin modified with polyrotaxane as a stress relaxation material
Authors: Ohtsuka Keiko , Zhao Changming
Published: April 2018

In this study, 4,4′‐diphenylmethane bismaleimide (BMI)/2,2′‐diallylbisphenol A (DABPA) resin was modified with polyrotaxane (PR) as a stress relaxation material. Based on a dynamic mechanical analysis and various properties of the cured resin, the influence of the motion of PR on the cured properties of BMI/DABPA/PR alloy is discussed. The cyclic molecule α‐cyclodextrin (α‐CD) that is threaded onto the PR axis contains a methacryl group in its side chain that reacts with the allyl group of BMI/DABPA resin. The methacryl group of PR reacted with the allyl group of BMI/DABPA matrix resin to form a transparent and dense network structure, so that the glass transition temperature was increased with increasing PR concentration. In addition, the toughness, impact resistance and adhesiveness of BMI/DABPA resin were improved by modification with PR. These results indicate that the poly(ethylene glycol) chain, which is the axial polymer of the PR, moves in the space formed by the cavities of the threaded α‐CD and the surrounding BMI/DABPA resin matrix in the glassy state, thereby relaxing the internal stress applied to BMI/DABPA/PR resin. The range of applications of BMI/DABPA resin modified with PR may expand into fields requiring high heat resistance in addition to excellent toughness and adhesiveness. © 2018 Society of Chemical Industry
Self‐sustained actuation from heat dissipation in liquid crystal polymer networks
Authors: Vantomme Ghislaine , Gelebart Anne Helene , Broer Dirk Jan , Meijer E. W.
Published: April 2018

Liquid crystal polymer networks (LCNs) lead the research geared toward macroscopic motion of materials. These actuators are molecularly programed to adapt their shape in response to external stimuli. Non‐photo‐responsive thin films of LCNs covered with heat absorbers (e.g., graphene or ink) are shown to continuously oscillate when exposed to light. The motion is governed by the heat dissipated at the film surface and the anisotropic thermal deformation of the network. The influence of the LC molecular alignment, the film thickness, and the LC matrix on the macroscopic motion is analyzed to probe the limits of the system. The insights gained from these experiments provide not only guidelines to create actuators by photo‐thermal or pure photo‐effects but also a simple method to generate mechanical oscillators for soft robotics and automated systems. © 2018 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1331–1336
Specific properties of in situ ruthenium‐catalyzed polyamide 12/polydimethylsiloxane compatibilized blend
Authors: Li Jing P. , Cassagnau Philippe , Espuche Eliane , Alcouffe Pierre , Bounor‐Legaré Véronique
Published: April 2018

The main objective of this work focused on the chemical modification of polyamide 12 (PA12) properties through the reaction with a hydride‐terminated polydimethylsiloxane (PDMS‐SiH). The investigated PA12/PDMS‐SiH blend was compatibilized by ruthenium derivative catalyzed hydrosilylation reaction in molten state. This original route enhanced interfacial adhesion and avoid PDMS‐SiH leaching phenomenon between the two immiscible phases. More specifically, the size of PDMS‐SiH domains in the blend decreased from around 4 μm to 800 nm and from 30 to 1 μm after compatibilization with 10 and 20 wt % PDMS‐SiH, respectively. For the best compatibilized PA12/PDMS‐SiH blend, the introduction of PDMS lowered the surface free energy and the PA12‐based blend turned from hydrophilic to hydrophobic behavior, as evidenced by the water contact angle measurements. Gas permeability and CO2/H2 and CO2/He gas selectivity were also improved with the increase in PDMS content. Besides, the mechanical properties were enhanced with 13% increase in Young's modulus after in situ compatibilization with 15 wt % PDMS‐SiH. Thermal stability was also improved after compatibilization as the initial degradation temperature of reactive blends obviously increased compared with nonreactive ones. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 978–988
Structural interaction and gas barrier properties of ethylene‐vinyl alcohol/tin phosphate glass composites
Authors: Lee Sangjin , Tyler Rakim , Maia Joao , Schiraldi David A.
Published: April 2018

The strength of interaction between tin phosphate glass (PGlass) filler droplets and an ethylene‐vinyl alcohol (EVOH) matrix were investigated by image, thermal, and rheological analysis. 10% PGlass droplets in EVOH were smaller than those previously observed in maleated polypropylene. Analysis using the Fox equation showed that EVOH/97 °C Tg PGlass composites are not miscible systems. Dynamic shear and extensional rheology data of those composites exhibited a weak physical network, with relaxation times longer than that of pure EVOH at all strain rates. The tensile properties of the EVOH/10 vol % PGlass composite showed it to be more ductile and flexible than a typical polymer/inorganic filler system, supporting interaction between PGlass and EVOH sufficient to interrupt polymer–polymer hydrogen bonding. While undrawn EVOH/PGlass composite films showed increased oxygen gas permeability when compared to undrawn neat EVOH film, the drawn composite films exhibited oxygen permeability 6–7 times lower than that of neat EVOH, attributed to the presence of high aspect ratio PGlass particles after orientation. The concept of hydrogen bonding between polymer and PGlass can likely be applied to other polymers such as polyamides which possess numerous hydrogen bonding sites. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 989–998
Ultrafast study of inter‐ and intrachain energy transfer in a core–polymer
Authors: Bolis Serena , Pasini Mariacecilia , Virgili Tersilla
Published: April 2018

Interchain interactions can play a positive role in reaching amplified spontaneous emission in an interesting core–polymer system where the donor (side chains) and the acceptor (core) are chemically linked together. Different degree of interchain interactions modifies the photophysical characteristics of the polymer. By means of transient absorption spectroscopy we show that the stimulated emission from the core decreases passing from solid state to concentrated solution and it is almost absent in the diluted solution. The conformational rearrangements of the core–polymer chain in solution limits the efficiency of the intrachain Förster energy transfer mechanism. The free chain rotations decrease the exciton hopping along the conjugated chains, the ratio between donor and acceptor moieties in the polymer, and change the relative orientation of the transition dipoles of the donor and acceptor causing a strong decrease of energy transfer efficiency and subsequently of the gain. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 965–969
Rtt109‐dependent histone H3 K56 acetylation and gene activity are essential for the biological control potential of Beauveria bassiana
Authors: Cai Qing , Wang Juan‐Juan , Shao Wei , Ying Sheng‐Hua , Feng Ming‐Guang
Published: April 2018

BACKGROUND

Rtt109 is a histone acetyltransferase that catalyzes histone H3K56 acetylation required for genomic stability, DNA damage repair and virulence‐related gene activity in yeast‐like human pathogens but remains functionally unknown in fungal insect pathogens. This study seeks to elucidate the catalytic activity of a Rtt109 orthologue and its possible role in sustaining the biological control potential of Beauveria bassiana, a fungal entomopathogen.

RESULTS

Deletion of rtt109 in B. bassiana abolished histone H3K56 acetylation and triggered histone H2A‐S129 phosphorylation. Consequently, the deletion mutant showed increased sensitivity to the stresses of DNA damage, oxidation, cell wall perturbation, high osmolarity and heat shock during colony growth, severe conidiation defects under normal culture conditions, reduced conidial hydrophobicity, decreased conidial UV‐B resistance, and attenuated virulence through normal cuticle infection. These phenotypic changes correlated well with reduced transcript levels of many genes that encode the families of H2A‐S129 dephosphorylation‐related protein phosphatases, DNA damage‐repairing factors, antioxidant enzymes, heat‐shock proteins, key developmental activators, hydrophobins and cuticle‐degrading Pr1 proteases respectively.

CONCLUSION

Rtt109 can acetylate H3K56 and dephosphorylate H2A‐S129 in direct and indirect ways respectively, and hence has an essential role in sustaining the genomic stability and global gene activity required for conidiation capacity, environmental fitness and pest control potential in B. bassiana. © 2018 Society of Chemical Industry
Selective dopamine D3 receptor antagonism significantly attenuates stress‐induced immobility in a rat model of post‐traumatic stress disorder
Authors: Rice Onarae V. , Ashby Charles R. , Dixon Clark , Laurenzo William , Hayden Jason , Song Rui , Li Jin , Tiwari Amit K. , Gardner Eliot L.
Published: April 2018

Post‐traumatic stress disorder (PTSD) is a debilitating psychiatric syndrome that occurs in individuals exposed to extremely threatening or traumatic events. In both animals and humans, dopamine (DA) function appears to be dysregulated in brain areas involved in the conditioned fear response(s) that underlie PTSD. In this study, we determined the effect of the selective DA D3 receptor antagonists YQA14A (6.25, 12.5 and 25 mg/kg i.p.) and SB‐277011A (6 mg/kg i.p.) on tone‐induced fear (assessed by measuring freeze time) in a modified version of the single‐prolonged stress (SPS) model of PTSD in adult male Sprague‐Dawley rats. Rats pretreated with vehicle and then subjected to restraint stress, forced swim and random foot shock (SPS) in the presence of a distinctive tone, displayed a significantly increased tone‐induced contextual freeze time and fecal pellet mass following re‐exposure to the tone. Rats pretreated with a single i.p. injection of 6.25 or 12.5 mg/kg of YQA14 or 6 mg/kg of SB‐277011A showed significantly attenuated contextual freeze time in the presence of the tone when tested 14 days after exposure to SPS. Overall, our results indicate that selectively antagonizing DA D3 receptors significantly decreases freezing time caused by an environment previously associated with stress. If our findings can be extrapolated to humans with PTSD, they suggest that DA D3 receptors may play a role in the pathophysiology of PTSD, and may have therapeutic utility for the clinical management of PTSD.
Prediction and prevention of small‐for‐gestational‐age neonates: evidence from SPREE and ASPRE
Authors: Tan M. Y. , Poon L. C. , Rolnik D. L. , Syngelaki A. , de Paco Matallana C. , Akolekar R. , Cicero S. , Janga D. , Singh M. , Molina F. S. , Persico N. , Jani J. C. , Plasencia W. , Greco E. , Papaioannou G. , Wright D. , Nicolaides K. H.
Published: April 2018

Objectives

To examine the effect of first‐trimester screening for pre‐eclampsia (PE) on the prediction of delivering a small‐for‐gestational‐age (SGA) neonate and the effect of prophylactic use of aspirin on the prevention of SGA.

Methods

The data for this study were derived from two multicenter studies. In SPREE, we investigated the performance of screening for PE by a combination of maternal characteristics and biomarkers at 11–13 weeks' gestation. In ASPRE, women with a singleton pregnancy identified by combined screening as being at high risk for preterm PE (> 1 in 100) participated in a trial of aspirin (150 mg/day from 11–14 until 36 weeks' gestation) compared to placebo. In this study, we used the data from the ASPRE trial to estimate the effect of aspirin on the incidence of SGA with birth weight < 10th, < 5th and < 3rd percentile for gestational age. We also used the data from SPREE to estimate the proportion of SGA in the pregnancies with a risk for preterm PE of > 1 in 100.

Results

In SPREE, screening for preterm PE by a combination of maternal factors, mean arterial pressure, uterine artery pulsatility index and serum placental growth factor identified a high‐risk group that contained about 46% of SGA neonates < 10th percentile born at < 37 weeks' gestation (preterm) and 56% of those born at < 32 weeks (early); the overall screen‐positive rate was 12.2% (2014 of 16 451 pregnancies). In the ASPRE trial, use of aspirin reduced the overall incidence of SGA < 10th percentile by about 40% in babies born at < 37 weeks' gestation and by about 70% in babies born at < 32 weeks; in babies born at ≥ 37 weeks, aspirin did not have a significant effect on incidence of SGA. The aspirin‐related decrease in incidence of SGA was mainly due to its incidence decreasing in pregnancies with PE, for which the decrease was about 70% in babies born at < 37 weeks' gestation and about 90% in babies born at < 32 weeks. On the basis of these results, it was estimated that first‐trimester screening for preterm PE and use of aspirin in the high‐risk group would potentially reduce the incidence of preterm and early SGA by about 20% and 40%, respectively.

Conclusion

First‐trimester screening for PE by the combined test identifies a high proportion of cases of preterm SGA that can be prevented by the prophylactic use of aspirin. © 2018 Crown copyright. Ultrasound in Obstetrics & Gynecology © 2018 ISUOG.
Gravitational corrections to Higgs potentials
Authors: Bounakis Marios , Moss Ian G.
Published: April 2018

Abstract

Understanding the Higgs potential at large field values corresponding to scales in the range above 1010GeV is important for questions of vacuum stability, particularly in the early universe where survival of the Higgs vacuum can be an issue. In this paper we show that the Higgs potential can be derived in away which is independent of the choice of conformal frame for the spacetime metric. Questions about vacuum stability can therefore be answered unambiguously. We show that frame independence leads to new relations between the beta functions of the theory and we give improved limits on the allowed values of the Higgs curvature coupling for stability.
The Role of Particle Size, Ballast, Temperature, and Oxygen in the Sinking Flux to the Deep Sea
Authors: Cram Jacob A. , Weber Thomas , Leung Shirley W. , McDonnell Andrew M. P. , Liang Jun‐Hong , Deutsch Curtis
Published: April 2018

The “transfer efficiency” of organic particles from the surface to depth is a critical determinant of ocean carbon sequestration. Recently, direct observations and geochemical analyses have revealed a systematic geographical pattern of transfer efficiency, which is highest in high latitude regions and lowest in the subtropical gyres. We evaluate the possible causes of this pattern using a mechanistic model of sinking particle dynamics. The model represents the size distribution of particles, the effects of mineral ballast, seawater temperature (which influences both particle settling velocity and microbial metabolic rates), and O2. Parameters are optimized within reasonable ranges to best match the observational constraints. Our model shows that no single factor can explain the observed pattern of transfer efficiency, but the biological effect of temperature on remineralization rate and particle size effects together can reproduce most of the regional variability with both factors contributing to low transfer efficiency in the subtropical gyres and high transfer efficiency in high latitudes. Particle density from mineral ballast has a similar directional effect to temperature and size but plays a substantially smaller role in our optimum solution, due to the opposing patterns of silicate and calcium carbonate ballasting. Oxygen effects modestly improved model fit by depressing remineralization rates and thus increasing transfer efficiency in the Eastern Tropical Pacific. Our model implies that climate‐driven changes to upper ocean temperature and associated changes in surface plankton size distribution would reduce the carbon sequestration efficiency in a warmer ocean.
Tectonic Topography Changes in Cenozoic East Asia: A Landscape Erosion‐Sediment Archive in the South China Sea
Authors: Yan Yi , Yao Deng , Tian Zhi‐Xian , Huang Chi‐Yue , Dilek Yildirim , Clift Peter D. , Li Zi‐An
Published: April 2018

The mode and tempo of Cenozoic fluvial input into the South China Sea by Asian rivers were strongly controlled by tectonically induced topographic changes and landscape development that resulted in repeated river captures and reversals. New Nd isotope and U‐Pb detrital zircon data from clastic sedimentary sequences in the northern South China Sea display secular variations reflecting significant changes in the compositions of fluvial sediment as well as changes in source rocks. The oldest, Eocene‐Oligocene (before ∼25 Ma) clastic rocks of the South China Sea contain sediments withɛNdvalues of −5 to −7.5 and detrital zircons of Cretaceous, Jurassic, and Permo‐Triassic, all derived from southern Cathaysia. The Oligocene‐Middle Miocene (∼25–11 Ma) sediments in the South China Sea strata displayɛNdvalues of −12 to −14 and Archean, Proterozoic, and Paleozoic detrital zircons, suggesting northern Cathaysia and/or the Yangtze Blocks as their provenance. The headward expansion of the Pearl River and reversal of the Middle Yangtze River correlates with the opening of the South China Sea and growth of the eastern Tibetan Plateau at ∼25 Ma. Further uplift of the eastern Tibetan Plateau and the Wuyi‐Nanling Mountains in SE China around 11 Ma reshaped the landscape and caused another phase of erosion—pattern adjustment and drainage—divide migration in East Asia, leading to the establishment of the modern fluvial systems of the Pearl, Minjiang, and Lower Yangtze Rivers.
Late Pliocene Marine pCO2 Reconstructions From the Subarctic Pacific Ocean
Authors: Swann George E. A. , Kendrick Christopher P. , Dickson Alexander J. , Worne Savannah
Published: April 2018

The development of large ice sheets across the Northern Hemisphere during the late Pliocene and the emergence of the glacial‐interglacial cycles that punctuate the Quaternary mark a significant threshold in Earth's climate history. Although a number of different mechanisms have been proposed to initiate this cooling and the onset of major Northern Hemisphere glaciation, reductions in atmospheric concentrations of CO2 likely played a key role. The emergence of a stratified (halocline) water column in the subarctic northwest Pacific Ocean at 2.73 Ma has often been interpreted as an event which would have limited oceanic ventilation of CO2 to the atmosphere, thereby helping to cool the global climate system. Here diatom carbon isotopes (δ13Cdiatom) are used to reconstruct changes in regional carbon dynamics through this interval. Results show that the development of a salinity stratification did not fundamentally alter the net oceanic/atmospheric flux of CO2 in the subarctic northwest Pacific Ocean through the late Pliocene/early Quaternary. These results provide further insights into the long‐term controls on global carbon cycling and the role of the subarctic Pacific Ocean in instigating global climatic changes.
Geophysical Measurements to Determine the Hydrologic Partitioning of Snowmelt on a Snow‐Dominated Subalpine Hillslope
Authors: Thayer Drew , Parsekian Andrew D. , Hyde Kevin , Speckman Heather , Beverly Dan , Ewers Brent , Covalt Matt , Fantello Nadia , Kelleners Thijs , Ohara Noriaki , Rogers Trent , Holbrook W. Steven
Published: April 2018

In subalpine watersheds of the intermountain western United States, snowpack melt is the dominant water input to the hydrologic system. The primary focus of this work is to understand the partitioning of water from the snowpack during the snowmelt period and through the remainder of the growing season. We conducted a time‐lapse electrical resistivity tomography (ERT) study in conjunction with a water budget analysis to track water from the snow‐on through snow‐off season (May–August 2015). Seismic velocities provided an estimate of regolith thickness while transpiration measurements from sap flow in conifer trees provided insight into root water uptake. We observed four hydrologic process‐periods and found that deep flow and tree water fluxes are the primary pathways through which water moves off of the hillslope. Overland flow and interflow were negligible. We observed temporal changes in vadose zone water content more than 3.0 m below the surface. Our results show that vertical flow through the thin soil mantle overlaying coarse colluvial regolith was the primary pathway to a local unconfined aquifer.
Focusing on Leadership to Improve Diversity in the Geosciences
Authors: Kirsch Robert
Published: April 2018

Sparks for Change Institute; Boulder, Colorado, 18–20 September 2017
New Simulation Supports Chicxulub Impact Scenario
Authors: den Hond Bas
Published: April 2018

Mountains ringing the center of Earth's most famous impact crater consist of porous rocks. Computer models of the impact can now predict those rocks’ microstructure.
Chemical Fluxes From a Recently Erupted Shallow Submarine Volcano on the Mariana Arc
Authors: Buck Nathaniel J. , Resing Joseph A. , Baker Edward T. , Lupton John E.
Published: April 2018

Hydrothermal discharge from submarine arc volcanoes is thought to be an important contributor to global hydrothermal budgets, but quantitative flux measurements are scarce. Ahyi Seamount, a shallow (<100 m) submarine intraoceanic arc volcano located in the Commonwealth of the Northern Mariana Islands, erupted in May 2014. In May and December 2014, we sampled the hydrothermal plume created by the eruption and estimated chemical fluxes from Ahyi by combining shipboard hull‐mounted Acoustic Doppler Current Profile current vector measurements with continuous and discrete Conductivity, Temperature, and Depth (CTD) data. Towed CTD sections were conducted perpendicular to the mean current direction: a sampling strategy that optimized chemical flux calculations by reducing complexities introduced by temporal variability in the speed and direction of plume dispersion. The Ahyi plume had an elevated optical backscatter signal accompanied by evidence of reduced chemical species and a lowered pH. We found enriched concentrations of H2, 3He, CH4, particulate S, Mn, and Fe, observations consistent with a highly active hydrothermal system. The fluxes of magmatic 3He and Fe from Ahyi were similar to that measured at three slow‐spreading ridge‐crest sites, whereas CH4 and Mn were 100–1,000 times lower. This is the first study to constrain export fluxes of a shallow submarine arc volcano into the euphotic zone. However, our data were collected soon after an eruption and thus may not be fully representative of the longer‐term chemical inputs from Ahyi.
Unlocking the role of MgO in the carbonation of alkali-activated slag cement
Authors: Park S. M. , Jang J. G. , Lee H. K.
Published: April 2018

MgO incorporation into alkali-activated slag cement reduces the rate of carbonation.
Dispersibility of carbon dots in aqueous and/or organic solvents
Authors: Zhao Pei , Zhu Liangliang
Published: April 2018

Carbon dots have a wide range of applications in biological and medical fields as an alternative to quantum dots because of their low toxicity and excellent luminescence properties.
Multi-color emission in monodispersed spheres of tetragonal yttrium phosphate: microwave-assisted fast synthesis, formation mechanism, temperature-dependent luminescence, and application in anti-fake labeling
Authors: Zhu Qi , Xu Zhixin , Wang Zhihao , Wang Xuejiao , Li Xiaodong , Sun Xudong , Li Ji-Guang
Published: April 2018

Well-dispersed spheres of yttrium phosphate synthesizedviamicrowave-assisted processing were used for application in anti-fake labeling.
Molecular dynamic simulation for thermal decomposition of RDX with nano-AlH3 particles
Authors: Li Cui-Fang , Mei Zheng , Zhao Feng-Qi , Xu Si-Yu , Ju Xue-Hai
Published: April 2018

Reactive molecular dynamic simulation of a high explosive, RDX, mixed with AlH3 nanoparticles was performed by a newly parameterized ReaxFF force field.
Precursor controlled synthesis of graphene oxide supported iron catalysts for Fischer–Tropsch synthesis
Authors: Wei Yuxue , Luo Dan , Zhang Chenghua , Liu Jingge , He Yurong , Wen Xiaodong , Yang Yong , Li Yongwang
Published: April 2018

Iron precursors are used to tune the structure and FTS performance of graphene oxide supported iron catalysts.
CO2 conversion to synthesis gas via DRM on the durable Al2O3/Ni/Al2O3 sandwich catalyst with high activity and stability
Authors: Zhao Yu , Kang Yunqing , Li Hui , Li Hexing
Published: April 2018

CO2 conversion to synthesis gas with a CO/H2 molar ratio around 1 was realized by using the dry reforming of methane reaction (DRM) at 800 °C.
Azidoheteroarylation of unactivated olefins through distal heteroaryl migration
Authors: Wang Min , Wu Zhen , Zhang Bo , Zhu Chen
Published: April 2018

A novel azidoheteroarylation of unactivated olefins by means of intramolecular distal heteroaryl migration is herein reported.
Highly efficient chlorine functionalized blue iridium(iii) phosphors for blue and white phosphorescent organic light-emitting diodes with the external quantum efficiency exceeding 20%
Authors: Miao Yanqin , Tao Peng , Gao Long , Li Xiangling , Wei Liuwei , Liu Shujuan , Wang Hua , Xu Bingshe , Zhao Qiang
Published: April 2018

Chlorine functionalized blue iridium(iii) phosphors (Ir1–Ir4) are designed for blue and white OLEDs with maximum EQEs of over 20%.
Adjustable high resolution window function
Authors: Stanković V.
Published: April 2018

In this letter, the authors introduce an adjustable window function that combines the ability of ultra‐spherical window function to control peak side‐lobe level and asymptotic side‐lobe attenuation, with the side‐lobe pattern of the Taylor–Villeneuve window function where side‐lobes near the main‐lobe have constant amplitude, which provides additional advantage over the ultra‐spherical window function of lower main‐lobe width. They proposed frequency and time domain window function designs that are obtained by modifying the properties of the power of Hann window function. In both cases, the asymptotic side‐lobe attenuation is given in closed form as a function of a single parameter.
25.78 Gbit/s data transmission over 2 km multi‐mode‐fibre with 850 and 910 nm single‐mode VCSELs and a commercial quad small form‐factor pluggable transceiver
Authors: Ledentsov N. , Agustin M. , Chorchos L. , Ledentsov N. N. , Turkiewicz J. P.
Published: April 2018

Dispersion in the multimode fibres (MMF) limits the transmission distance of the modern data communication networks. The authors show that the use of single‐mode (SM) vertical cavity surface emitting lasers (VCSELs) in combination with the receiver module of a commercially available transceiver can increase the transmission distance to several kilometres. They report 25.78 Gbit/s error‐free transmission over 1800 m of multimode fibre with 850 nm and 1400 m with 910 nm SM VCSELs. Data transmission up to 2600 and 2400 m can be achieved with BER below 3.8×10−3 forward error correction limit accordingly. The use of multiple wavelengths demonstrates the opportunity to increase the capacity of MMF links with shortwave wavelength division multiplexing.
Novel coherent radar high‐speed manoeuvering target detection method
Authors: Wang Jing , Guo Ping , Li Yin‐wei , Wu Dong‐mei , Chen Li‐fu
Published: April 2018

A novel coherent high‐speed manoeuvering target detection method based on the parameterised autocorrelation function and three‐dimensional integration is presented. The parameterised autocorrelation function realises the searching parameters replacement and reduces the noise correlation without the signal energy loss. Consequently, compared to two representative detection methods, the proposed method can strike a balance between the computational cost and detection performance without the blind speed sidelobe.
Mathematical method for air electrostatic discharge circuits calculation
Authors: Xinggang Liu , Ming Wei , Xiaofeng Hu
Published: April 2018

Here, a new analytical method, state matrix transform method, is proposed for calculating the descriptions of current waveforms generated by commercial electrostatic discharge (ESD) generators. This method can be used to analyse and design lumped parameter ESD circuits. A relatively simple eight elements ESD circuit model is established and used to predict the current waveform of human‐metal ESD events. To calibrate the ESD simulator, a mathematical expression of four exponentials curve for ESD current waveform is given. This careful theoretical study of ESD current waveform calculation makes an innovative contribution to ESD generator circuit simulation and design, and it provides a new mathematical description for ESD sensitivity test.
Efficient protection scheme for low‐voltage DC micro‐grid
Authors: Som Shreyasi , Samantaray Subhransu Ranjan
Published: April 2018

Detection of shorted DC faults and high‐resistance faults on ring type low‐voltage DC (LVDC) micro‐grids imposes an elusive challenge. This research work proposes an efficient and reliable protection scheme for DC system in order to boost up LVDC system adoption on large scale, despite lack of proper standards and mature experience in DC system protection. In order to ameliorate these deficiencies, a wavelet transform‐based fast fault protection scheme using local measurements has been proposed for eliminating threat to voltage source converters during fault. The features extracted using wavelet coefficients are utilised as key indicators to identify the fault with wide variations in operating conditions. The LVDC micro‐grid system has been simulated using real‐time digital simulator and the test results studied show a great potential ability in performing DC fault detection and classification task efficiently. Furthermore, the robustness of the proposed protection scheme is capable of fault line identification and setting up desired relay selectivity in the LVDC distribution system.
Global power grid interconnection for sustainable growth: concept, project and research direction
Authors: Rafique Syed Furqan , Shen Pei , Wang Zhe , Rafique Rizwan , Iqbal Tahir , Ijaz Salman , Javaid Umair
Published: April 2018

Transcontinental grid interconnection and clean energy development for sustainability are the prime objectives to address through global energy interconnection (GEI) platform. Key issues can be solved through GEI such as environmental pollution, climate change, resources scarcity and unbalanced development. The growing concern of fossil fuel depletion leads to the exploitation of renewable energy which is mostly located on Arctic and Equator zones. This study addresses about the importance, current projects and research directions of clean energy, smart grid, ultra‐high voltage transmission, grid interconnection trends around the world in order to globally interconnect the future grid. The review results provide comprehensive background knowledge to all the researchers in order to investigate further into the field.
Islanding detection of synchronous distributed generators using data mining complex correlations
Authors: Gomes Eduardo A.P. , Vieira José C.M. , Coury Denis V. , Delbem Alexandre C.B.
Published: April 2018

This study proposes a novel method based on data mining for islanding detection of synchronous distributed generators. The method uses a new technique called data mining of code repositories (DAMICORE), which is a powerful data mining tool for detecting patterns and similarities in various kinds of datasets. In addition, a trip logic was developed in this proposal in order to detect islanding and disconnect the distributed generator. One of the most relevant features of the proposed method is its capability to generalise, which reduces the need of big datasets for training purposes. This approach has been tested with islanding, load switching and fault simulations, presenting promising results concerning performance, as well as detection time. General results showed a better performance of the method if compared to traditional anti‐islanding protection schemes, such as frequency‐based relays.
Three‐dimensional thermal modelling of transformers in transformer room for spatial and temporal failure analysis
Authors: Tao Wang , Qianggang Wang , Peng Wang
Published: April 2018

Temperature is a key factor for failure analysis of power transformers. Conventionally, transformer failure rate is calculated with hot spot temperature induced from IEEE empirical equations. This article firstly introduces a spatial and temporal related failure model based on three‐dimensional thermal simulations of transformer and the related environment. The proposed thermal model is established with computational fluid dynamics for ventilation calculation and heat generation equations for power device simulation. Cooling strategies and mutual heating effect of power equipment are considered for an accurate temperature distribution prediction. By incorporating the three‐dimensional thermal model into the service life‐dependent and temperature‐dependent model, the failure rate of each spatial point in power transformer could be calculated according to Arrhenius theory and Weibull distribution. The simulation results show that the proposed model clearly improves the accuracy of failure analysis and can be used for thermal and ventilation design of transformer room.
Oscillation centre identification method based on frequency characteristics in multi‐source oscillation scenes
Authors: Ma Jing , Deng Zhuojun , Zhang Yongxin , Li Pei , Thorp James S.
Published: April 2018

Concerning multi‐source oscillation scenes, an oscillation centre identification method based on the variation trend of bus frequency is proposed. First, according to the amplitude and phase relationship between voltage and current at any point in the system, the functional expression of the frequency of voltage and current is derived. Then, the variation trend and distribution of the frequency of voltage and current in multi‐source oscillation scenes are analysed. On this basis, the relationship between system frequency distribution and the oscillation centre and desynchronising centre is revealed, and an oscillation centre identification scheme for multi‐source oscillation scenes is put forward. Simulation results based on DIgSILENT/PowerFactory demonstrate that the proposed scheme can effectively identify the location of oscillation centre in multi‐source oscillation system.
SG parameters estimation based on synchrophasor data
Authors: Ahmadzadeh‐Shooshtari Babak , Torkzadeh Roozbeh , Kordi Meysam , Marzooghi Hesamoddin , Eghtedarnia Fariborz
Published: April 2018

In this study, first, it is shown that the least‐squares (LS) algorithm outperforms well known methods such as extended Kalman filter and unscented Kalman filter for synchronous generator (SG) parameters estimation using phasor measurement unit (PMU) data. However, as the LS algorithm may estimate the SG parameters inaccurately if the initial values of SG model state variables are not valid, a modified LS (MLS) algorithm, which estimates the initial values of SG model state variables alongside SG parameters, is proposed. In addition to parameters estimation of an SG classical model, the performance of this algorithm in the estimation of whole electromagnetic parameters and rotor inertia constant of an SG full‐order model is evaluated. Note that conventionally, measurements of generators rotor angles were used to estimate SGs full‐order model parameters; nevertheless, in the proposed MLS algorithm, online SG parameters estimation is accomplished using PMU data without relying on rotor angle measurement that is difficult to be obtained in practise. Simulation results demonstrate the effectiveness of the proposed algorithm in SG parameters estimation for various disturbances and noisy measurements. Furthermore, the effect of mechanical torque signal unavailability on the proposed algorithm capability is studied, where the efficacy of this algorithm is proven.
Cuckoo Search approach enhanced with genetic replacement of abandoned nests applied to optimal allocation of distributed generation units
Authors: de Oliveira Victoria Y.M. , de Oliveira Rodrigo M.S. , Affonso Carolina M.
Published: April 2018

Here, it is presented a novel Cuckoo Search (CS) algorithm called Cuckoo‐GRN (Cuckoo Search with Genetically Replaced Nests), which combines the benefits of genetic algorithm (GA) into the CS algorithm. The proposed method handles the abandoned nests from CS more efficiently by genetically replacing them, significantly improving the performance of the algorithm by establishing optimal balance between diversification and intensification. The algorithm is used for the optimal location and size of distributed generation units in a distribution system, in order to minimise active power losses while improving system voltage stability and voltage profile. The allocation of single and multiple distribution generation units is considered. The proposed algorithm is extensively tested in mathematical benchmark functions as well as in the 33‐bus and 119‐bus distribution systems. Simulation results show that Cuckoo‐GRN can lead to a substantial performance improvement over the original CS algorithm and others techniques currently known in literature, regarding not only the convergence but also the solution accuracy.
Optimal reactive power resources sizing for power system operations enhancement based on improved grey wolf optimiser
Authors: Taha Ibrahim B. M. , Elattar Ehab E.
Published: April 2018

In recent years, optimal sizing and location of reactive power resources are drawing much attention to help the operators of the utilities to enhance the power system operations. Therefore, this work presents a new version of grey wolf optimiser (GWO) to solve the problem of optimal reactive power resources sizing for power system operation enhancement. The proposed method which called improved grey wolf optimiser (IGWO) can be derived by modifying the exploration–exploitation balance in the conventional GWO to enhance its rate of convergence. Also, the weighted distance strategy is employed in the proposed IGWO to overcome the drawback of the conventional GWO. Optimal reactive power resources sizing problem is non‐linear and non‐convex optimisation problem. To solve this problem, different objective functions are used. These objective functions are minimisation of generating cost, minimisation of transmission power loss and voltage profile improvement. The validity and superiority of the proposed IGWO method are tested using three standard IEEE systems for normal and contingency conditions. Then the results are compared with those obtained from other recently published algorithms. The simulation results show that the proposed IGWO method is more accurate and efficient than other recently published algorithms.
Optimal stochastic scheduling of thermal‐wind GENCOs trading in the day‐ahead market including bilateral contracts with BSS
Authors: Gong Naiwei , Luo Xianjue , Ma Honglian , Wang Qi , Wang Kaiyan
Published: April 2018

With the traditional vertically integrated electric market transforming into a liberalised one, the generation side consisting of various generation companies (GENCOs) is separated from the grid. This transformation gives opportunity for GENCOs to enhance their own profits by expanding business. One example is to establish bilateral contracts directly with the end users. This study considers a thermal‐wind GENCO trading with the grid in the pool‐based electricity energy market and meanwhile signs bilateral contracts with a battery swapping station (BSS). The operation framework for this GENCO to maximise its profit under uncertain information is proposed. A two‐stage stochastic model is adopted to formulate the profit of the GENCO with the uncertain wind power, electricity market price and stochastic BSS electricity demand. The stochastic problem is transformed into deterministic mixed‐integer linear programme and solved by CPLEX. The impact of bilateral contract capacity, contract price, degree of uncertainties and the wind power penetration on the final profit is analysed. This work provides a novel operation framework for GENCOs, and provides feasible bidding strategy and scheduling under uncertain conditions, especially for GENCOs owning renewable energy.
Fast distribution network reconfiguration with graph theory
Authors: Huang Shengjun , Dinavahi Venkata
Published: April 2018

Owing to mixed‐integer and non‐linear properties, the distribution network reconfiguration (DNRC) problem has been widely addressed with meta‐heuristic algorithms. To accelerate the solution process, two essential components of meta‐heuristic algorithms are investigated in this study: solution representation and fitness evaluation. Instead of the popular binary and integer numbers, decimal encoding is employed. Decoding is based on the proposed probability‐based loop destruction strategy. The fitness evaluation is based on the power flow calculation of radial network. Different from backward/forward sweep method, the advantageous direct solution technique is utilised, where the matrix generation process has been accelerated. Both improvements are based on the graph theory and fully explained with illustrative examples. Case studies are implemented on five benchmark systems. The superiority of the proposed methods over their advanced counterparts has been established with intensive comparisons. Finally, these methods are integrated into a standard particle swarm optimisation framework for the solution of DNRC. Results indicate that the proposals significantly improve the solution efficiency without the loss of quality.
Optimising departure intervals for multiple bus lines with a multi‐objective model
Authors: Feng Jiaxiao , Ye Zhirui , Wang Chao , Chang Cheng , Xu Mingtao , Sun Cuicui
Published: April 2018

A multi‐objective model was developed to optimize departure intervals synchronously for multiple bus lines. Then, a Genetic Algorithm with “Elitist Preservation” strategy combining the economical method of “dynamic scoring” (GA‐EPDS) was proposed to solve the multi‐objective model. The proposed method included three objectives: the first objective was to maximize the bus operation profits; the second objective was to minimize the passengers’ transfer waiting time; and the last one was to minimize passengers’ costs. Transfer waiting time was crucial for multiple bus lines and long transfer waiting time would decrease the satisfaction of passengers, so transfer waiting time was regarded as a single objective. In addition, an evaluation function, which was obtained through a “dynamic scoring” method, was formulated to estimate whether the three objective functions reached a global optimum. In order to improve the solution generated in terms of computational effort and convergence, a GA‐EPDS was designed to solve the multi‐objective model. Finally, the proposed approach was applied in a case study of an actual network. The numerical results based on different scale instances and different traffic conditions demonstrate that our proposed model and method are effective and feasible to optimize departure intervals for multiple bus lines.
Predicting the future location of cars on urban street network by chaining spatial web services
Authors: Hazeghi Aghdam Arash , Alesheikh Ali Asghar
Published: April 2018

The use of web services for analysing and visualising maps has received great attention recently, because the complicated analysis of spatial data requires different processes to be run consecutively. Predicting the future location of a vehicle on a street network is one of the most challenging analyses used for improving context‐aware location‐based services, intelligent transportation systems and criminology. In this research, the authors present a new short‐term prediction algorithm and explore the required analyses and web services. They present an appropriate method for chaining these web services to predict location(s). To assess their methodology, they developed a prototype system and tested for trajectories in Beijing. This system calculates the prediction time for a specified car to show the predicted future location in the street network. Their results showed that the average transferred data volume increases as the prediction period increases. The results also showed that the prediction algorithm has 75% accuracy at 1 min and 87.5% accuracy at 2 and 3 min. The implemented chaining method reduces the complexity of the location prediction algorithm for users because they do not need to know the processes. The outputs from this system can be used as input parameters for other web‐based applications.
Multi‐level pedestrian signalisation atlarge four‐leg roundabouts
Authors: Xu Hongfeng , Zhang Kun , Zheng Qiming , Yao Ronghan
Published: April 2018

Pedestrian accessibility to a large four‐leg roundabout can be improved by locating staggered crosswalks on all roundabout legs and signalising them to allow for two‐stage crossing. A multi‐level pedestrian signalisation (MPS) is developed for such roundabouts to balance pedestrian accessibility and vehicle mobility. With appropriate application of traffic control devices and traffic detection systems, the right‐of‐way is assigned to pedestrians and vehicles in three actuated modes. Signals at adjacent crosswalks can operate independently or as a group in a specific mode of right‐of‐way to prioritise pedestrians or vehicles. A number of traffic events are defined to autonomously manage signal operations second by second. Simulation results indicated that MPS had good operational stability and offered sufficient capacity for a large four‐leg roundabout to serve traffic demand varying in a wide range. The appealing operational advantage of the MPS‐enabled roundabout over the fully actuated conventional intersection may help prevent large four‐leg roundabouts from being converted to conventional intersections.
Facilitation of air traffic control via optical character recognition‐based aircraft registration number extraction
Authors: Vidakis Dimitrios G. , Kosmopoulos Dimitrios I.
Published: April 2018

To identify any aircraft in the world, it is sufficient to read its registration number. This number is a unique identifier, and offers valuable information, in the same way a car registration number does. In this work, the authors present the results of their feasibility study towards a simple, yet very efficient and effective system to identify aircrafts using video‐optical character recognition acquired by off‐the‐shelf cameras. They used several videos under realistic conditions at the Heraklion airport during high season and they achieved very promising results. They claim that there is much room for the development of a low‐cost airport surface monitoring system based on standard cameras, which can complement high‐cost radars.