bluuebunny/crossref_metadata_2025 huggingface dataset:
Comment on “Sedimentary and Tectonic Evolution of the Southern Qiangtang Basin: Implications for the Lhasa‐Qiangtang Collision Timing” by A. Ma et al.
Authors: Chen Wei‐Yan , Hu Xiu‐Cheng , Zhong Yun , Fu Yuan‐Bin , Li Fang , Wang Yu‐Guang
Published: August 2018

Ma et al. (2017, https://doi.org/10.1002/2017JB014211) proposed that the Lhasa‐Qiangtang collision commenced in late Bathonian time (~166 Ma), based on the observation of an angular unconformity that truncated the Bathonian Buqu Formation from the late Bathonian‐early Callovian Biluoco Formation and the recognition of siliciclastic provenance switch from arc igneous source to uplifted orogenic source in the Biluoco‐Qixiangco area of the southern Qiangtang basin. Unfortunately, however, extensive exposure of Late Jurassic‐Middle Cretaceous ophiolite fragments and marine sedimentary rocks along the Bangong suture zone indicates that the Bangong Meso‐Tethys Ocean did not close until the Late Cretaceous, which is consistent with a Late Jurassic‐Middle Cretaceous magmatic arc in the southern Qiangtang terrane as well as paleomagnetic data. The late Bathonian orogenic event in the southern Qiantang area observed by Ma et al. (2017, https://doi.org/10.1002/2017JB014211) can be explained by subduction of oceanic highs on the Bangong Meso‐Tethyan Ocean. Clearly, our submission is a significant clearance to Ma et al.'s work and the Tibetan Plateau geology and of timely significance in correctly understanding the evolution history of the Tibetan Plateau. Therefore, our paper possibly is of broad interest to our international colleagues.
Elastic Softening of Limestone Upon Decarbonation With Episodic CO2 Release
Authors: Head Dulcie , Vanorio Tiziana , Clark Anthony C.
Published: August 2018

Reactive transport under confining stress through porous media leads to complex, coupled feedback mechanisms between chemical and physical alteration. We exposed four intact limestone cores to hydrothermal conditions conducive to the wollastonite‐producing decarbonation reaction. We allowed for the episodic release of pore pressure to mimic pulsing flow in crustal systems and mitigate the accumulation of carbon dioxide (CO2). Energy‐dispersive X‐ray spectroscopy results show that all four reacted samples developed a new calc‐silicate phase during the reaction. Alteration from the fluid‐mediated reaction was pervasive but nonuniform, resulting in the development of a small volume of highly compliant pore space with grain contact softening. Lower initial velocity sensitivity to confining pressure and higher initial pore connectivity lead to more development of soft porosity. The relevance of the results lies in enhancing seismic monitoring capabilities of potentially seismogenic areas—large decreases in observed seismic velocity in limestone undergoing decarbonation can only be accounted for if the nonnegligible change in the elastic properties of the rock frame are understood. Since the potential for seismicity of a subsurface system depends both on the elastic stiffness and stress state of the rocks, rocks undergoing reactive transport cannot be modeled as though their elastic moduli are time independent. Accurate modeling of the subsurface behavior depends on understanding not just the particular rock reactions taking place but also the initial pore network and velocity sensitivity to confining pressure of those rocks, and how the elastic properties of that rock evolve.
Lunar Cold Spots and Crater Production on the Moon
Authors: Williams J.‐P. , Bandfield J. L. , Paige D. A. , Powell T. M. , Greenhagen B. T. , Taylor S. , Hayne P. O. , Speyerer E. J. , Ghent R. R. , Costello E. S.
Published: August 2018

Mapping of lunar nighttime surface temperatures has revealed anomalously low nighttime temperatures around recently formed impact craters on the Moon. The thermophysically distinct “cold spots” provide a way of identifying the most recently formed impact craters. Over 2,000 cold spot source craters were measured with diameters ranging from 43 m to 2.3 km. Comparison of the crater size‐frequency distribution with crater chronology models and crater counts of superposed craters on the ejecta of the largest cold spot craters constrains the retention time of the cold spots to no more than ~0.5–1.0 Myr with smaller cold spots possibly retained for only few hundred kyr. This would suggest a relatively rapid impact gardening rate with regolith overturn depths exceeding ~5 cm over this time scale. We observe a longitudinal heterogeneity in the cold spot distribution that reflects the Moon's synchronous rotation with a higher density of cold spots at the apex of motion. The magnitude of the asymmetry indicates the craters formed from a population of objects with low mean encounter velocities ~8.4 km/s. The larger cold spots (D > 800 m) do not follow this trend, and are concentrated on the trailing farside. This could result from a shorter retention time for larger cold spots on the leading hemisphere due to the greater number of smaller, superposed impacts. Alternatively, the abundance of large cold spots on the trailing farside resulted from a swarm of 100‐m‐scale impactors striking the Moon within the last ~0.5 Myr.
High‐Resolution, Ground‐Based Observations of the Lunar Sodium Exosphere During the Lunar Atmosphere and Dust Environment Explorer (LADEE) Mission
Authors: Kuruppuaratchi D. C. P. , Mierkiewicz E. J. , Oliversen R. J. , Sarantos M. , Derr N. J. , Gallant M. A. , Rosborough S. A. , Freer C. W. , Spalsbury L. C. , Gardner D. D. , Lupie O. L. , Roesler F. L.
Published: August 2018

We present the first comprehensive set of lunar exospheric line width and line width derived effective temperatures as a function of lunar phase (66° waxing phase to 79° waning phase). Data were collected between November 2013 and May 2014 during six observing runs at the National Solar Observatory McMath‐Pierce Solar Telescope by applying high‐resolution Fabry‐Perot spectroscopy (R ~ 180,000) to observe emission from exospheric sodium (5,889.9509 Å, D2 line). The 3‐arc min field of view of the instrument, corresponding to ~336 km at the mean lunar distance (384,400 km), was positioned at several locations off the lunar limb; only equatorial observations taken out to 950 km are presented here. We find the sodium effective temperature distribution to be approximately a symmetric function of lunar phase with respect to full Moon. Within magnetotail passage we find temperatures in the range of 2500–9000 K. For phase angles greater than 40° we find that temperatures flatten out to ~1700 K.
Predicting Nitrate Retention at the Groundwater‐Surface Water Interface in Sandplain Streams
Authors: Stelzer Robert S. , Scott J. Thad
Published: August 2018

Groundwater‐surface water ecotones present opportunities for nitrate retention because changes in organic carbon availability, redox potential, and nitrate demand often occur at these locations. Although there have been many measurements of nitrate retention and denitrification at the groundwater‐surface water interface, few investigators have quantitatively predicted where nitrogen transformation occurs in this zone. Our main objective was to describe and predict spatial variation in nitrate retention and removal in shallow groundwater among and within streams in the central sand plains of Wisconsin. We predicted that nitrate transformation rates would be positively related to nitrate and particulate organic carbon availability, a negative nonlinear function of dissolved oxygen availability, and would peak at intermediate rates of groundwater discharge. Five sites on four streams were chosen that spanned an order of magnitude in groundwater nitrate concentration. Nitrate retention and N2 production were quantified by determining how nitrate and N2 fluxes changed along nominal 55‐cm groundwater flow paths. Nitrogen transformation was widespread but highly variable within the study sites. Partial least squares regression models explained a much larger amount of variation in nitrate retention and N2 production at the local scale than at the regional scale. Dissolved oxygen availability and groundwater discharge were the most consistent predictors of nitrate retention at both scales. We conclude that nitrate retention at the groundwater‐surface water interface can be predicted but that more research is necessary to determine if nitrate transformation at this ecotone can be modeled at broader scales.
Climate Change to Offset Improvements in Watershed Acid‐Base Status Provided by Clean Air Act and Amendments: A Model Application in Shenandoah National Park, Virginia
Authors: Robison Andrew L. , Scanlon Todd M.
Published: August 2018

The impact of climate change on watershed acid‐base chemistry is currently understudied. Projecting the future condition of upland watersheds in the southern Appalachians of the United States, where high sulfate adsorption has prevented significant acid‐base recovery, is complicated because of the unknown interaction with likely changes in temperature and precipitation. Here the biogeochemical model PnET‐BGC and statistically downscaled general circulation models were used to evaluate potential effects of future climate on watershed biogeochemistry at White Oak Run in Shenandoah National Park, Virginia. Downscaled climate scenarios on average predict warmer temperatures and greater precipitation for this watershed by the end of the century. Model results suggest the combination of these effects on discharge drive the largest changes in acid‐base chemistry, as increased runoff depletes the soil pool of sulfur and base cations resulting in lower stream concentrations. Superimposed on this abiotic effect is an increased biotic demand for base cations, resulting in an overall loss of alkalinity under projected climate conditions. The predicted loss of alkalinity resulting from climate change is comparable to what would be expected if acid deposition had remained elevated during this century. Specifically, model results indicate the predicted loss of alkalinity resulting from climate change would offset about 68 +/−16% of the modeled gains from the Clean Air Act and Amendments, where the 95% uncertainty bounds are associated with the ensemble of climate predictions applied to the calibrated biogeochemical model. Such an outcome would represent a considerable setback from one of the desired effects of clean air regulation.
Ocean Circulation in the Toarcian (Early Jurassic): A Key Control on Deoxygenation and Carbon Burial on the European Shelf
Authors: Ruvalcaba Baroni Itzel , Pohl Alexandre , van Helmond Niels A. G. M. , Papadomanolaki Nina M. , Coe Angela L. , Cohen Anthony S. , van de Schootbrugge Bas , Donnadieu Yannick , Slomp Caroline P.
Published: August 2018

The Toarcian Oceanic Anoxic Event (T‐OAE, ∼183 Myr) was a long‐lasting episode of ocean deoxygenation during the Early Jurassic. The event is related to a period of global warming and characterized by major perturbations to the hydrological and carbon cycles with high rates of organic matter burial in shelf seas. Ocean circulation during the Toarcian and its influence on marine biogeochemical cycles are still not fully understood. Here we assess the spatial extent of anoxia in the NW Tethys Ocean during the T‐OAE, the relationship with ocean circulation and the impact on organic carbon burial, using new and existing sedimentary records from the European Epicontinental Shelf in combination with general circulation model results. We demonstrate that bottom waters on the southwestern part of the shelf were mainly oxic during the T‐OAE, while those in the northeastern basins were mostly anoxic or even sulfidic. Results for two ocean‐atmosphere models (Fast Ocean‐Atmosphere Model and Massachusetts Institute of Technology general circulation model) suggest the presence of a strong clockwise gyre over the European Epicontinental Shelf, which brought oxygenated equatorial waters from the Tethys Ocean to the southern shelf. The northward limb of the gyre was significantly weakened due to the rough bathymetry of the northern shelf, making this relative small region highly sensitive to local ocean stratification. These sluggish ocean dynamics promoted bottom water anoxia and enhanced burial of organic carbon in the northeastern basins, which accounted for 3–5% of the total carbon extracted from the ocean‐atmosphere system as recorded by the positive carbon isotope shift.
Prediction of the Dst Index and Analysis of Its Dependence on Solar Wind Parameters Using Neural Network
Authors: Lethy Ahmed , El‐Eraki Mohamed A. , Samy Aalaa , Deebes Hanafy A.
Published: August 2018

In this work, we propose an artificial neural network (ANN) with seven input parameters for the prediction of disturbance storm time (Dst) index 1 to 12 hr ahead. The ANN uses past near‐Earth solar wind parameter values to forecast the Dst. The input parameters are the solar wind interplanetary magnetic field, north‐south component of interplanetary magnetic field, temperature, density, speed, pressure, and electric field. The ANN was trained on the data period from 1 January 2007 to 31 December 2015, which contains 78,888 hourly data samples. While the period from 1 January 2016 to 31 May 2017 was used to test the prediction capabilities of the ANN. Several ANN structures were tested and the best results were determined using the correlation coefficient (R) during the training and prediction phases. The results indicate an adequate accuracy of R = 0.876 for prediction 2 hr in advance and R = 0.857 for prediction 12 hr in advance. The power of the proposed ANN was illustrated using the strongest six storms recorded during the prediction period. Generally, the duration and number of the input parameters significantly affect the training and prediction performance of the applied ANN. The results are outstanding in term of accuracy when considering a medium‐term prediction of 12 hr in advance and in terms of timing of the Dst minimum occurrence. In addition, the results show a strong dependence on the solar wind electric current.
Deriving highly oriented organic nanofibers and ternary memory performance via salification-induced effects
Authors: Zhang Cheng , Li Yang , Zhou Yan , Zhang Qijian , Li Hua , Lu Jianmei
Published: August 2018

A novel pyridine-based organic conjugated molecule (NCPy) has been successfully synthesized and converted into an organic pyridinium salt (NCPy-salt). Highly oriented organic nanofibers and high-quality films were obtained by transforming the molecule to a salt form. This transformation also resulted in a unique ternary resistive switching memory behavior.
Popcorn-shaped polyethylene synthesised using highly active supported permethylindenyl metallocene catalyst systems
Authors: Buffet Jean-Charles , Turner Zoë R. , O’Hare Dermot
Published: August 2018

Unsymmetrical permethylindenyl bent metallocene complexes have been synthesised and reacted with inorganic solid supports to afford highly active catalysts for the slurry phase polymerisation of ethylene with desirable, low aggregation, “popcorn” morphology.
Target induced reconstruction of DNAzymatic amplifier nanomachines in living cells for concurrent imaging and gene silencing
Authors: Li Jun-Jie , Li Wan-Ning , Du Wen-Fang , Lv Meng-Mei , Wu Zhen-Kun , Jiang Jian-Hui
Published: August 2018

A novel DNAzymatic amplifier nanomachine that enables the functions of concurrent mRNA imaging and gene silencing in living cells has been reported.
2-Methylimidazole-assisted synthesis of a two-dimensional MOF-5 catalyst with enhanced catalytic activity for the Knoevenagel condensation reaction
Authors: Guo Changyan , Zhang Yonghong , Zhang Li , Zhang Yi , Wang Jide
Published: August 2018

A novel and facile strategy was developed for the synthesis of a 2D MOF-5 catalyst with 2-methyimidazole as regulation reagent and a Lewis basic site, which showed excellent catalytic activity in Knoevenagel condensation.
PbWO4 nanofibers for shielding gamma radiation: crystal growth, morphology and performance evaluation
Authors: Xu Yun-Chuan , Zhang Quan-Ping , Liu Jun-Hua , Wu You , Liu Li-Ping , Xu Dui-Gong , Zhou Yuan-Lin
Published: August 2018

Assembling anisotropic structures with versatility such as good thermal conductivity and mechanical loading for radiation shielding has recently attracted widespread attention.
Facile synthesis of tin-doped mayenite electride composite as a non-noble metal durable electrocatalyst for oxygen reduction reaction (ORR)
Authors: Khan Karim , Khan Tareen Ayesha , Li Jia , Khan Usman , Nairan Adeela , Yuan Yao , Zhang Xuyang , Yang Minghui , Ouyang Zhengbiao
Published: August 2018

In this study, we synthesized nanosized Sn-doped C12A7:e− (C12Al7−xSnx:e−, where x = 0.20 to 1) composite with high surface area of 244 m2 g−1.
Volatile oil from alpinia officinarum promotes lung cancer regression in vitro and in vivo
Authors: Li Ning , Zhang Qingyu , Jia Zhenbin , Yang Xiaohong , Zhang Haitao , Luo Hui
Published: August 2018

The anti-lung cancer activity of volatile oil from Alpinia officinarum (VOAO) and the underlying mechanism has been studied. VOAO could be an effective, low cytotoxicity candidate for lung cancer intervention.
Circ008913,viamiR-889 regulation of DAB2IP/ZEB1, is involved in the arsenite-induced acquisition of CSC-like properties by human keratinocytes in carcinogenesis
Authors: Xiao Tian , Xue Junchao , Shi Ming , Chen Chao , Luo Fei , Xu Hui , Chen Xiong , Sun Baofei , Sun Qian , Yang Qianlei , Dai Xiangyu , Zhang Aihua , Tang Huanwen , Liu Qizhan
Published: August 2018

Circ008913,viamiR-889 regulation of DAB2IP/ZEB1, is involved in the arsenite-induced acquisition of CSC-like properties and the neoplastic transformation.
Facile synthesis of chiral indolines through asymmetric hydrogenation of in situ generated indoles
Authors: Yu Chang-Bin , Wang Jie , Zhou Yong-Gui
Published: August 2018

A concise synthesis of chiral indolines has been developed through intramolecular condensation, deprotection and palladium-catalyzed asymmetric hydrogenation in a one-pot process with up to 96% ee. A strong Brønsted acid played an important role in both the formation of indoles and asymmetric hydrogenation process.
B-site doping effects of NdBa0.75Ca0.25Co2O5+δ double perovskite catalysts for oxygen evolution and reduction reactions
Authors: Kim Nam-In , Cho Sung-Hwa , Park Se Hwan , Lee Young Joo , Afzal Rana Arslan , Yoo Jeseung , Seo Young-Soo , Lee Yun Jung , Park Jun-Young
Published: August 2018

NdBa0.75Ca0.25Co2O5+δ-based double perovskite catalysts provide new ways for significantly enhanced oxygen-related electrochemical reactions with durable characteristics in alkaline atmospheres.
Achieving superior cycling stability byin situforming NdH2–Mg–Mg2Ni nanocomposites
Authors: Luo Qun , Gu Qinfen , Liu Bin , Zhang Teng-Fei , Liu Wenqing , Li Qian
Published: August 2018

Nd4.3Mg87.0Ni8.7alloy exhibits excellent cycling stability up to 819 cycles which is attributed to thein situformation of NdH2–Mg–Mg2Ni nanocomposites.
Controlling the contact angle of biological sessile drops for study of their desiccated cracking patterns
Authors: Chen Ruoyang , Zhang Liyuan , Shen Wei
Published: August 2018

Controlling the initial contact angle of biological sessile drops to advance the study and applications of their desiccated cracking patterns.
Adaptive threshold reception scheme for OFDM‐PWM‐based visible light communication systems
Authors: Zhang Tian , Yang Zhiqing , Sun Jianing , Qiao Shuang
Published: August 2018

The adaptive threshold reception scheme for OFDM pulse‐width modulation (OFDM‐PWM)‐based visible light communication systems is presented. The authors first implement the adaptive threshold algorithm to modify the discrete OFDM‐PWM sampling signal. Then, the unit periodic integral is employed for the modified time‐domain sampling sequence to accurately calculate the pulse width of each OFDM‐PWM sample. The proposed reception scheme is robust to the additive white Gaussian noise superimposed on the amplitude of the received OFDM‐PWM signals. The experimental results show that the proposed adaptive threshold reception scheme has a better BER performance compared with the traditional OFDM.
Double waveguide method to retrieve the electromagnetic parameters of biaxial anisotropic materials
Authors: Xu Xiaofei
Published: August 2018

A double waveguide (DW) method is proposed to retrieve the electromagnetic (EM) parameters of biaxial anisotropic materials. The material under test in this method is not needed to change its orientation, making the measurement much easier. Accurate closed forms are given to predict the constitutive material parameters by using the correlation relationship between the DWs. As a proof‐of‐concept example, one homogeneous biaxial anisotropic medium is considered. The material parameters are numerically extracted using the DW method, which are in good agreement with the given ones, indicating the method is effective.
Low‐noise dynamic comparator circuit with selectable input‐referred thermal noise voltage
Authors: Yazid M.
Published: August 2018

A new method for reducing input‐referred thermal noise of dynamic comparator circuit without increasing load capacitance as commonly used in the conventional method is proposed. An implementation circuit with selectable low‐noise mode operation is presented, which enable both low‐noise mode and standard mode operation by a single circuit. Simulation in 180 nm CMOS process technology shows that the proposed new method and circuit topology can achieve up to 90% increase in gain of comparator first stage, resulting in up to 40% decrease in input‐referred thermal noise voltage, compared with a conventional circuit with similar load capacitance. The proposed circuit is also able to operate with similar performance as the conventional circuit when low‐noise mode operation is not necessary.
Capacitor mismatch calibration method for SAR ADC with minimum area and power penalty
Authors: Yang Xiaolin , Zhao Menglian , Wu Xiaobo
Published: August 2018

A novel capacitor mismatch calibration method is presented to compensate the capacitor mismatches in a successive approximation register (SAR) ADC. The method features a new weight‐balancing split capacitive DAC which allows automatic extraction and calibration of the capacitor mismatches by itself. As a result, the ADC's resolution can be substantially improved with minimum area and power penalty. The calibration method was verified and implemented in a 14 bit, 10 kS/s SAR ADC, fabricated in a 0.13 µm standard CMOS process. The measured signal‐to‐noise‐plus‐distortion and spurious‐free dynamic range are 72.7 and 86 dB after calibration with 13.6 and 21.8 dB improvements, respectively. The total power consumption is 15.2 µW at a 1.2 V supply voltage.
DV‐hop localisation algorithm based on optimal weighted least square in irregular areas
Authors: Yan Xiaoyong , Sun Lijuan , Zhou Jian , Song Aiguo
Published: August 2018

In distance vector (DV)‐hop localisation, the estimated distances between unknown nodes and anchors are usually determined through multiplying the hop‐count and the average per‐hop distance, so the per‐hop distance represents a physical distance. Unfortunately, in practice, wireless communication networks may be affected by the environment, which makes the per‐hop distance deviating from the physical distance. A number of improved DV‐hop localisation algorithms have been proposed previously, which give the weight to the per‐hop distance. When applied as it is, sub‐optimal results were achieved as the differences between per‐hop distances and physical distances could not be determined. In this Letter, the authors analyse the error during the process of converting hop distances to physical distances and take advantage of the optimal weighted function, which achieves a more accurate distance conversion model. Then, they correct the estimated position of unknown nodes according to the relationship between the estimated distances calculated by hop‐distance conversion and the distances from the estimated positions of unknown nodes to anchor nodes. The simulation results show that the localisation performance of the proposed algorithm is better than the existing weighted methods in irregular areas.
Multiuser virtual reality environment for visualising neuroimaging data
Authors: Shattuck David W.
Published: August 2018

The recent advent of high‐performance consumer virtual reality (VR) systems has opened new possibilities for immersive visualisation of numerous types of data. Medical imaging has long made use of advanced visualisation techniques, and VR offers exciting new opportunities for data exploration. The author presents a new framework for interacting with neuroimaging data, including MRI volumes, neuroanatomical surface models, diffusion tensors, and streamline tractography, as well as text‐based annotations. The system was developed for the HTC Vive using C++, OpenGL, and the OpenVR software development kit. The author developed custom GLSL shaders for each type of data to provide high‐performance real‐time rendering suitable for use in a VR environment. These are integrated with an interface that enables the user to manipulate the scene through the Vive controllers and perform operations such as volume slicing, fibre track selection, and structural queries. The software can read data generated by existing automated brain MRI analysis packages, enabling the rapid development of subject‐specific visualisations of multimodal data or annotated atlases. The system can also support multiple simultaneous users, placing them in the same virtual space to interact with each other while visualising the same datasets, opening new possibilities for teaching and for collaborative exploration of neuroimaging data.
Performance analysis of cooperative NOMA with a shared AF relay
Authors: Li Yan , Li Yongzhao , Chen Yunfei , Ye Yinghui , Zhang Hailin
Published: August 2018

Non‐orthogonal multiple access (NOMA) has been proposed as a promising technique for the fifth generation wireless networks. In this study, the authors investigate the performance of a cooperative relaying scheme using NOMA (termed NOMA‐AF‐CRS), where two sources communicate with their corresponding destinations over the same frequency simultaneously through a shared amplify‐and‐forward (AF) relay. First, the closed‐form approximations are derived for the outage probability. The analytical results are further evaluated in the high signal‐to‐noise ratio region to characterise the diversity order achieved by the system. Then, the ergodic sum capacity of NOMA‐AF‐CRS is analysed and an upper bound to the ergodic sum capacity is derived. Finally, simulation results are presented to verify the proposed analysis and demonstrate the advantages of NOMA‐AF‐CRS over the conventional orthogonal multiple access techniques.
Cogging torque reduction by eccentric structure of teeth in external rotor permanent magnet synchronous motors
Authors: Wang Kai , Liang Yanping , Wang Dongmei , Wang Chenguang
Published: August 2018

Aiming at the problem of torque ripple caused by cogging torque in the external rotor permanent magnet synchronous motor, this study proposes a method for reducing the cogging torque by the eccentric structure of stator teeth. Taking a 3 kW external rotor permanent magnet synchronous motor as an example, the validity of the method proposed is verified by theoretical analysis and finite element calculation. Finally, the other performances of the models with different teeth eccentricities are compared, and a prototype is manufactured to verify the correctness of the simulation results. The research shows that the eccentric structure of stator teeth does not affect the other performances of the motor greatly while reducing the cogging torque of external rotor permanent magnet synchronous motor effectively.
Impact of control system on small‐signal stability of hybrid multi‐infeed HVDC system
Authors: Guo Chunyi , Liu Wei , Zhao Jian , Zhao Chengyong
Published: August 2018

This paper focuses on the impact of control system on small‐signal stability of the Hybrid Multi‐Infeed HVDC(H‐MIDC) system, in which the Line‐Commutated‐Converter based HVDC (LCC‐HVDC) and Voltage‐Sourced‐Converter based HVDC (VSC‐HVDC) links feed into an AC system in close mutual proximity. A comprehensive linearized small‐signal model is developed for an H‐MIDC system. Based on the eigenvalue analysis and participation factor analysis, the inherent oscillatory modes of the H‐MIDC system are revealed. Then, the impact of the most sensitive control system parameters on the least‐damped modes are investigated. The studies show that (i) the proportional gains of PLL functions of LCC and VSC stations, and AC voltage outer loop controller of VSC station are highly coupled, and presents the most sensitivity to the least damped modes; (ii) parameters of PLL in LCC station, and outer loop of AC voltage control and PLL in VSC station can highly impact the damping of the oscillatory modes and even cause instability, and (iii) smaller PLL gains in LCC and VSC stations, and smaller proportional gain of AC voltage control of VSC station are preferable and can enhance damping of dominant modes.
Demand response potential evaluation for residential air conditioning loads
Authors: Chen Xingying , Wang Jixiang , Xie Jun , Xu Shuyang , Yu Kun , Gan Lei
Published: August 2018

Residential air conditioning loads with energy storage characteristics can quickly participate in the demand response, making it an important demand response resource. It can improve resource utilisation and the flexibility of power grid operation through the effective regulation. However, the degree of residential air conditioning to participate in demand response is affected by the outdoor temperature, users’ comfort settings, thermal storage and insulation properties of buildings. Moreover, the difficulty of assessing the demand response potential is further increased by the uncertainty of the influencing factors. To guide the residential air conditioners to participate in the power grid operation, the aggregated air conditioner model is established to describe the relationship among the total power, the external environment, and the indoor temperature. The demand response potential model is established from the amount and the duration of demand response. The effects of outdoor temperature, indoor temperature adjustment and the number of air conditioners participating in the response are quantitatively evaluated. Finally, the accuracy of the aggregated model and demand response potential model are verified by numerical simulation.
Smart PV and SmartPark inverters as suppressors of TOV phenomenon in distribution systems
Authors: Rangarajan Shriram Srinivasarangan , Collins E. Randolph , Fox J. Curtiss
Published: August 2018

This study proposes a new application and a novel control scheme for utilising Smart PV and Smart Park inverters to mitigate temporary overvoltage (TOV) phenomenon in distribution systems. As more number of the inverter‐based distributed generators such as PV are connected to a medium‐ and low‐voltage distribution systems, TOV phenomenon becomes more prevalent during single line to ground fault. Currently, the IEEE 142 ‘Effective grounding’ technique has been the reference for various grounding schemes to prevent TOV. This study explores the potential of low‐cost and a novel solution for the first time that utilises a specialised controller associated with PV/SmartPark inverters (Smart inverters) as a TOV suppressor. The efficacy of the aforementioned novel application has been demonstrated on a simplified benchmark system of the IEEE Standard 399‐1997 with few modifications. A 4 MW conventional PV plant is considered along with 10 MVAR Smart inverter connected to the point of common coupling. During normal operation of the distribution systems, the Smart inverter controller acts in a voltage regulation mode to curtail the voltage rise due to reverse power flow from the 4 MW PV plant. During a fault condition, the TOV sensor enables the TOV control to suppress the violated limits of voltages in the healthy phases to an acceptable value.
Universal model‐based fault location for improved system integrity
Authors: Ananthan Sundaravaradan Navalpakkam , Santoso Surya
Published: August 2018

Transmission lines are a vital part of power systems and are prone to a variety of short‐circuit faults. It is imperative to identify the fault location to restore the system as quickly as possible for maintaining the system integrity. Impedance‐based fault location algorithms are most commonly used but they are prone to several sources of error such as fault resistance and mutual coupling between the lines and may not provide accurate results in the presence of complex network configurations such as three‐terminal lines. Though information about mutual coupling or knowledge of complex network configuration is known, they cannot be directly used in impedance‐based fault location algorithms. This study proposes a novel automated generic framework for model‐based fault location approach which uses the power system model to overcome the shortcomings of impedance‐based fault location methods. A combination of power system simulation software and a control and processing software provide the flexibility to be able to incorporate all the available information about the system to accurately estimate the fault location. Furthermore, this study provides key insights to implement the proposed framework in an effective and efficient manner by using reduced equivalent circuits.
Method to resolve false trip of non‐directional overcurrent relays in radial networks equipped with distributed generators
Authors: Ghotbi Maleki Mahdi , Mohammadi Chabanloo Reza , Javadi Hamid
Published: August 2018

The connection of distributed generation sources to the distribution network has negative effects on the network protection such as; a false trip of non‐directional overcurrent relays. In this study, an offline method is proposed to overcome the false trip issue. In this method, the false trip is modelled as a new set of coordination constraints in the optimal coordination problem. For establishing false trip constraints, pickup current setting and characteristic type of relays are selected in addition to the time multiplier setting. Considering false trip constraints in the coordination problem increases the operating time of relays. Therefore, the optimisation is applied to obtain the settings of non‐directional overcurrent relays in order to reduce their operating times in addition to resolving the false trip. Also, three new approaches are defined for pickup current selection based on pickup current range. A combination of genetic algorithm and linear programming technique is used to access optimised responses. Finally, the proposed method is implemented on a sample radial distribution network and the results demonstrated that the occurrence of the false trip was prevented and also the operating time of the relays was reduced to an acceptable level.
Multi‐objective approach to maximise loadability of distribution networks by simultaneous reconfiguration and allocation of distributed energy resources
Authors: Quadri Imran Ahmad , Bhowmick Suman , Joshi Dheeraj
Published: August 2018

In recent years, continuously increasing load demand and deficiency of capital resources vis‐à‐vis a competitive electricity market have forced transmission and distribution utilities worldwide to maximise the efficiency and utilisation of their existing infrastructure. This study presents a multi‐objective approach to maximise the loadability of distribution networks by simultaneous reconfiguration and optimal allocation of distributed energy resources using a comprehensive teaching‐learning‐based optimisation algorithm. The proposed technique is based on the ɛ‐constraints method and uses a graphical approach for network reconfiguration. Loadability enhancement is validated on the IEEE 33‐bus and 69‐bus radial distribution systems. Several case studies are carried out to demonstrate the effectiveness of the proposed approach in reducing the network active power losses, improving the kVA loading margins and enhancing the voltage profiles while considering voltage and thermal limit constraints. Results show that maximum loadability is obtained with simultaneous network reconfiguration and multiple DER allocation with varying power factors.
Multi‐stage co‐planning framework for electricity and natural gas under high renewable energy penetration
Authors: Nunes Juliana Barbosa , Mahmoudi Nadali , Saha Tapan K. , Chattopadhyay Debabrata
Published: August 2018

This study develops a new multi‐stage (dynamic) approach for the co‐planning of power and gas systems to deal with variable renewable energy resources (VREs). The model is formulated using a stochastic programming framework to accurately capture the unfolding of both short and long‐term uncertainties faced by power and gas systems. The effects of high renewable energy penetration and renewable energy uncertainty in both systems are assessed while determining the optimal investment and operation decisions in several stages of the planning horizon. To prove the benefits of the proposed approach, the authors compare the results of the authors’ framework with other methods used in the literature. The effectiveness of the framework is validated on a realistic case of Queensland, Australia, in which both networks are driven to capture the link between these systems and to accommodate the state's unique features of renewable availability. The results demonstrate that their dynamic approach provides more robust outcomes compared to other methods as it allows adapting the expansion plans to unexpected changes in the future. The analysis also shows that a transition towards renewable energy presents a higher cost, different investment strategies, and lower gas‐fired consumption compared to the terminal renewable target.
Multi‐stage restoration strategy for service restoration in distribution systems considering outage duration uncertainty
Authors: Sharma Anurag , Trivedi Anupam , Srinivasan Dipti
Published: August 2018

This study proposes a multi‐stage restoration strategy to solve the service restoration problem in distribution systems considering the uncertainty of outage duration. Furthermore, it also proposes a restoration index defined in terms of (i) priority of the load restored, (ii) number of switching operations, and (iii) estimated likelihood of the restoration solution to assist the utility in enhanced decision‐making. Service restoration is formulated as a single objective optimisation problem considering the maximising of the restoration index as the only objective. A decentralised multi‐agent system method is developed to solve the service restoration problem considering controlled islanding of distributed generators. The uncertainty of outage duration is estimated using the maximum entropy principle‐based on the cause of the fault. Exhaustive case studies are implemented on a small 38 bus and a large 119 bus test distribution system to demonstrate the effectiveness of the proposed multi‐stage restoration strategy to restore the system under outage duration uncertainty.
Accurate and comprehensive fault location algorithm for two‐terminal transmission lines
Authors: Poudineh‐Ebrahimi Farhad , Ghazizadeh‐Ahsaee Mahdi
Published: August 2018

In this study, a novel accurate fault location algorithm is presented for two‐terminal transmission lines. In contrast to conventional methods, the proposed algorithm not only utilises asynchronous samples recorded during the fault but also needs no line parameters and identification of fault type. In the presented fault‐locating method, distributed parameter line model in the time domain and asynchronous data of the terminals collected during fault are applied. Fault locating as an optimisation problem has been solved by the heuristic algorithm of teaching–learning‐based optimisation, and the decision variables of fault location, synchronisation time and line parameters are estimated simultaneously. The performance of the presented method was tested with different fault incidence angles, a variety of fault types, and under several system and fault conditions using the MATLAB/Simulink. These tests demonstrate the high accuracy of the presented method. Also, the proposed method did not show any dependence on the impedance of the Thevenin sources of the two sides of the line, the fault impedance and the fault incidence angle. Furthermore, it was not affected by the high resistance of the fault and the network structure.
Application of let‐through energy to back‐up over‐current protection on high‐voltage feeders
Authors: Slabbert Martin J. , Bansal Ramesh C. , Naidoo Raj
Published: August 2018

Let‐through energy (LTE) refers to the I2 t or Joule energy that a conductor is exposed to during a fault on the feeder. This energy is influenced by the magnitude of the fault current and time it takes for the protection system to clear the fault. If the LTE exceeds the conductor thermal energy limit, the conductor will get damaged. This concept of LTE evaluation is applied to the inverse definite minimum time (IDMT) current based back‐up protection elements on a multisource high‐voltage feeder in a hypothetical and actual network. Another method to calculate the relay operating time for IDMT relays was developed based on an average disk speed of electromechanical over‐current relay and the proportionality of its speed to the magnitude of the fault current. This method was incorporated into a software application to generate results. These results allow the user to evaluate the conductor LTE exposure, total fault time exposure, the effect of instantaneous fault clearing and the application of auto‐reclose cycles. An energy‐area evaluation was applied to quantify and evaluate small protection settings changes. The conclusion is that LTE analysis on back‐up protection should be considered for high‐voltage feeders to ensure that the conductors are protected.
Circumferentially conformal slot array antenna and its Ka‐band multibeam applications
Authors: Liu Yi , Yang Hu , Jin Zusheng , Zhu Jiang
Published: August 2018

A standing‐wave slot array covered with a two‐layer dielectric slab based on substrate integrated waveguide (SIW) technology, which is circumferentially conformed to a cylinder, is designed, fabricated and measured at Ka‐band. The radiating part consists of seven slotted cylindrical SIWs, each of which has four‐element longitudinal slots. Several such slot arrays fed by Rotman lenses are grouped on a cylinder along the circumferential direction to cover a 2D field of view. The microstrip Rotman lens is employed as the beamforming network with seven input ports, which can generate a corresponding number of beams to cover −35° to 35° along 1D (E‐plane). Another dimension (H‐plane) is covered from −52° to 52° with four beams generated by the slot arrays group. A prototype antenna is fabricated, the measured results demonstrate its ability of scanning over a 2D field of view with multiple beams. This type of multibeam conformal antenna is a good candidate for high‐speed vehicles or communication base stations requiring electronic beam‐scanning capabilities and considering conformal reasons.
Beam‐switching antenna implemented by reconfigurable slots on cylindrical cavity
Authors: Li Eric S. , Cheng Jui‐Ching , Lee Shin‐Chih , Kuo Yu‐Hsuan
Published: August 2018

A design for beam‐switching antennas is proposed in this study. A cylindrical cavity with a reconfigurable conformal slot array distributed evenly along the middle of its side wall is presented. The reconfigurable feature of the slots is achieved by placing a diode switch across each slot. An integrated bias scheme is introduced for the diode switches to activate and disable the slots. By properly selecting the dimensions for the cavity and the number of activated slots, the optimum values for the gain and front‐to‐back ratio (FBR) of the antenna can be obtained. The gain value is further increased by adding a skirt‐like structure to both the top and bottom of the cavity. A design example is presented with the operating frequency set at 5.8 GHz. The conformal array comprises 24 slots to provide a 15° resolution for main beam switching. The simulation results indicate that the design can offer an antenna gain up to 8.62 dBi and a FBR above 10 dB. These results and the corresponding radiation patterns have gone through experimental verification, from which good agreement is observed.
Game theory based bidding strategy for prosumers in a distribution system with a retail electricity market
Authors: Liang Zheming , Su Wencong
Published: August 2018

Distributed energy resources (DERs) are deployed vastly to reduce carbon emission, improve power quality and maintain the reliability of distribution systems. With the introduction of new players, such as prosumers, which are constructed with DERs, distribution system operators (DSOs) are facing changes in the retail electricity market. Prosumers need a well‐defined strategic bidding mechanism to maximize their operation revenue, while DSOs need a new market clearing mechanism for the changed retail electricity market. Thus, an innovative game‐theoretic market framework for a prosumer‐centric retail electricity market is proposed. A bilevel algorithm is adopted to model new features of DSOs, utility companies and prosumers. The supply function equilibrium model, Nikaido–Isoda functions, and relaxation algorithms are applied to analyse the competition among key participants in a retail electricity market. Extensive simulation results are employed to illustrate and validate the effectiveness of the proposed framework for bidding strategies of prosumers with a retail electricity market. Specifically, the strategy with dumping‐bid or abnormal‐bid from a prosumer is suppressed by the market operator in the model. Moreover, the sensitivity analysis shows that the proposed framework can handle various numbers of prosumers in the retail electricity market with reasonable computational time and convergence rate.
Symmetry features for license plate classification
Authors: Raghunandan Karpuravalli Srinivas , Shivakumara Palaiahnakote , Padmanabhan Lolika , Hemantha Kumar Govindaraju , Lu Tong , Pal Umapada
Published: August 2018

Achieving high recognition rate for license plate images is challenging due to multi‐type images. We present new symmetry features based on stroke width for classifying each input license image as private, taxi, cursive text, when they expand the symbols by writing and non‐text such that an appropriate optical character recognition (OCR) can be chosen for enhancing recognition performance. The proposed method explores gradient vector flow (GVF) for defining symmetry features, namely, GVF opposite direction, stroke width distance, and stroke pixel direction. Stroke pixels in Canny and Sobel which satisfy the above symmetry features are called local candidate stroke pixels. Common stroke pixels of the local candidate stroke pixels are considered as the global candidate stroke pixels. Spatial distribution of stroke pixels in local and global symmetry are explored by generating a weighted proximity matrix to extract statistical features, namely, mean, standard deviation, median and standard deviation with respect the median. The feature matrix is finally fed to an support vector machine (SVM) classifier for classification. Experimental results on large datasets for classification show that the proposed method outperforms the existing methods. The usefulness and effectiveness of the proposed classification is demonstrated by conducting recognition experiments before and after classification.