bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved Aerosol Retrievals Over Complex Regions Using NPP Visible Infrared Imaging Radiometer Suite Observations
Authors: Yang Yikun , Zhao Chuanfeng , Sun Lin , Wei Jing
Published: April 2019

As a new generation of polar‐orbiting satellites, NPP VIIRS (National Polar‐orbiting Partnership Visible Infrared Imaging Radiometer Suite) provides important supports for the studies of local and global scale climate change, environmental monitoring, and radiant energy balance. This paper proposed an improved deep blue aerosol retrieval algorithm over complex regions based on NPP VIIRS observations. Two improvements were proposed and implemented to the traditional aerosol optical depth (AOD) retrieval algorithm in order to improve the retrieval accuracy, including the construction of the surface reflectance conversion model and aerosol optical parameter acquisition. The retrieval results were extensively evaluated. First, the accuracy of the algorithm was evaluated using AErosol RObotic NETwork ground‐based observations, including conditions over different underlying surfaces, different seasons, and different AOD values. Then, the cross validation was carried out between our AOD retrievals and NPP VIIRS aerosol products. The verification results show that our AOD retrievals agree very well with the AErosol RObotic NETwork AOD with coefficient of determination (R2) ~ 0.85. The improved deep blue algorithm performs well overall under different surface conditions and seasons, while the quality of performance gradually decreases with the increase of AOD. Moreover, the improved algorithm is robust with less bias, root‐mean‐square error, and relative mean bias in the AOD retrievals and can provide more detailed aerosol information compared with the NPP VIIRS aerosol products. These results suggest that the improved deep blue algorithm can obtain high‐precision AOD information, providing better data basis for related researches on air pollution and climate change.
Mono‐Model Parameter Joint Inversion by Gramian Constraints: EM Methods Examples
Authors: Ogunbo J. N.
Published: April 2019

Joint inversions of coincident geophysical data are usually constrained to produce more reliable subsurface models. Structural, petrophysical, model parameter correlation, empirical, and transforms are some of the published constraints. The Gramian constraint provides a broad mathematical framework for implementing the aforementioned constraints. The Gramian constraint is formed from the determinant of the inner products of the model parameters involved. Previous works have used the Gramian constraint to invert multimodal parameters of different geophysical methods. But there has not been any extension of Gramian‐constrained joint inversion to mono‐model parameter from similar geophysical methods, for example, a similar conductivity or resistivity model from time‐ and frequency‐domain airborne electromagnetic methods. I implement the Gramian‐constrained joint inversion of time‐ and frequency‐domain airborne EM (AEM) data. This implementation allows the Gramian constraint to enhance the linear correlation of the model parameter between the two methods as the number of iterations increases. Improvement of the final joint inversion results over the standalone models is noticeable for both 3% noise‐contaminated synthetic and field data experiments. The field data jointly inverted are the high moment time‐domain SkyTEM data and frequency‐domain RESOLVE helicopter EM data acquired over the salinized Bookpurnong Irrigation District in South Australia in 2006 and 2008, respectively.
What Climate Models Get Wrong About Future Water Availability
Authors: Underwood Emily
Published: April 2019

Models that accurately represent past and present rainfall provide more accurate projections of water availability, a new study suggests.
Putting the Cloud to Work for Seismology
Authors: MacCarthy Jonathan , Marcillo Omar , Trabant Chad
Published: April 2019

The cloud infrastructure developed in the business community has made access to cluster computing possible for even the smallest research groups, enabling new kinds of research workflows in geophysics.
Fiber-Optic Networks Find a New Use as Seismic Sensor Arrays
Authors: Wang Herbert , Comas Xavier , Tyler Scott
Published: April 2019

Distributed Acoustic Sensing: Principles and Case Studies; Washington, D.C., 9 December 2018
Mapping Heat Vulnerability to Protect Community Health
Authors: McCarthy Kelly , Valdez Zack
Published: April 2019

Community leaders and scientists from two U.S. cities are combining public health data and heat maps to prepare residents for climate change–related health risks.
House Climate Crisis Committee Hears Call for Action from Youth
Authors: Showstack Randy
Published: April 2019

The witnesses and Democrats at the House hearing urge action, but Republicans question the committee’s focus and criticize Democrats on the committee for not working in a bipartisan manner.
Effects of Increasing Aridity on Ambient Dust and Public Health in the U.S. Southwest Under Climate Change
Authors: Achakulwisut Pattanun , Anenberg Susan C. , Neumann James E. , Penn Stefani L. , Weiss Natalie , Crimmins Allison , Fann Neal , Martinich Jeremy , Roman Henry , Mickley Loretta J.
Published: April 2019

The U.S. Southwest is projected to experience increasing aridity due to climate change. We quantify the resulting impacts on ambient dust levels and public health using methods consistent with the Environmental Protection Agency's Climate Change Impacts and Risk Analysis framework. We first demonstrate that U.S. Southwest fine (PM2.5) and coarse (PM2.5‐10) dust levels are strongly sensitive to variability in the 2‐month Standardized Precipitation‐Evapotranspiration Index across southwestern North America. We then estimate potential changes in dust levels through 2099 by applying the observed sensitivities to downscaled meteorological output projected by six climate models following an intermediate (Representative Concentration Pathway 4.5, RCP4.5) and a high (RCP8.5) greenhouse gas concentration scenario. By 2080–2099 under RCP8.5 relative to 1986–2005 in the U.S. Southwest: (1) Fine dust levels could increase by 57%, and fine dust‐attributable all‐cause mortality and hospitalizations could increase by 230% and 360%, respectively; (2) coarse dust levels could increase by 38%, and coarse dust‐attributable cardiovascular mortality and asthma emergency department visits could increase by 210% and 88%, respectively; (3) climate‐driven changes in dust concentrations can account for 34–47% of these health impacts, with the rest due to increases in population and baseline incidence rates; and (4) economic damages of the health impacts could total $47 billion per year additional to the 1986–2005 value of $13 billion per year. Compared to national‐scale climate impacts projected for other U.S. sectors using the Climate Change Impacts and Risk Analysis framework, dust‐related mortality ranks fourth behind extreme temperature‐related mortality, labor productivity decline, and coastal property loss.
Induced Seismicity Reduces Seismic Hazard?
Authors: Barbour Andrew J. , Pollitz Fred
Published: April 2019

Earthquakes caused by human activities have been observed for decades. Often these are related to industrial activities pumping fluids into deep geologic formations, like with wastewater disposal. The simplest theory connecting these processes to earthquakes is straightforward: injection leads to fluid pressure changes that either reduce the strength of preexisting faults or generate new faults. In practice, the conditions that lead to induced earthquakes are not always clear in ways that can be generalized. Kao et al. (2018, https://doi.org/10.1029/2018GL079288) show how the distribution of induced earthquakes in Western Canada relate to natural rates of deformation in the crust. Using these new results, they discuss an intriguing paradox: induced seismicity can cause short‐term increases in the seismic hazard that are followed by a period of reduced seismic hazard. Such hazard‐reducing scenarios are plausible but hinge upon simplifying assumptions about how the crust stores and releases strain energy in the form of earthquakes.
Satellite‐Based Estimation of Cloud Top Radiative Cooling Rate for Marine Stratocumulus
Authors: Zheng Youtong , Rosenfeld Daniel , Zhu Yannian , Li Zhanqing
Published: April 2019

Cloud top radiative cooling rate (CTRC) is the leading term in the energy budget of a marine boundary layer capped by stratocumulus. It plays a significant role in the formation, evolution, and maintenance of the stratocumulus cloud system. This study demonstrates the feasibility of estimating the CTRC, with high accuracy, from passive satellite data only. The estimation relies on a radiative transfer model with inputs from satellite‐retrieved cloud parameters in combination with reanalysis sounding that is revised, in a physically coherent way, by satellite data. The satellite‐based estimates CTRC agree with ground‐based ones to within ~10%. The high accuracy largely benefits from the good capability of satellite data in constraining parameters of most influence to the CTRC such as free‐tropospheric sounding, cloud top temperature, and cloud optical depth. Applying this technique, we generate a climatology of CTRC during summer over the Southern Hemisphere tropical and subtropical oceans.
Deep Structure of the Lunar South Pole‐Aitken Basin
Authors: James Peter B. , Smith David E. , Byrne Paul K. , Kendall Jordan D. , Melosh H. Jay , Zuber Maria T.
Published: April 2019

The South Pole‐Aitken basin is a gigantic impact structure on the far side of the Moon, with an inner rim extending approximately 2,000 km in the long axis dimension. The structure and history of this basin are illuminated by gravity and topography data, which constrain the subsurface distribution of mass. These data point to the existence of a large excess of mass in the Moon's mantle under the South Pole‐Aitken basin. This anomaly has a minimum mass of 2.18 × 1018 kg and likely extends to depths of more than 300 km. Plausible sources for this anomaly include metal from the core of a differentiated impactor or oxides from the last stage of magma ocean crystallization. Although the basin‐forming impact event likely excavated the vast majority of the preexisting crust, the present‐day crust of the basin interior is at least 16 km thick in undisturbed regions.
Pacing of Red Sea Deep Water Renewal During the Last Centuries
Authors: Felis Thomas , Mudelsee Manfred
Published: April 2019

The Red Sea is a deep marine basin often considered as small‐scale version of the global ocean. Hydrographic observations and ocean‐atmosphere modeling indicate Red Sea deep water was episodically renewed by wintertime open‐ocean deep convections during 1982–2001, suggesting a renewal time on the order of a decade. However, the long‐term pacing of Red Sea deep water renewals is largely uncertain. We use an annually resolved coral oxygen isotope record of winter surface water conditions to show that the late twentieth century deep water renewals were probably unusual in the context of the preceding ~100 years. More frequent major events are detected during the late Little Ice Age, particularly during the early nineteenth century characterized by large tropical volcanic eruptions. We conclude that Red Sea deep water renewal time is on the order of a decade up to a century, depending on the mean climatic conditions and large‐scale interannual climate forcing.
On the Importance of Gradients in the Low‐Energy Electron Phase Space Density for Relativistic Electron Acceleration
Authors: Allison Hayley J. , Horne Richard B. , Glauert Sarah A. , Del Zanna Giulio
Published: April 2019

Observations of the electron radiation belts have shown links between increases in the low‐energy seed population and enhancements in the >1‐MeV flux. During active times, low‐energy electrons are introduced to the radiation belt region before being accelerated to higher energies via a range of mechanisms. The impact of variations in the seed population on the 1‐MeV flux level were explored using the British Antarctic Survey Radiation Belt Model. We find that, for a period from the 21 April to 9 May 2013, the increase in the low‐energy electron flux was vital to recreate the observed 1‐MeV flux enhancement on the 1 May but was less important for the 1‐MeV enhancement on the 27 April 2013. To better understand the relationships between the different energy populations, a series of idealized experiments with the 2‐D British Antarctic Survey Radiation Belt Model were performed, which highlight a careful balance between losses and acceleration from chorus waves. Seed population enhancements alter this balance by increasing the phase space density gradient, and consequently, the rate of energy diffusion, allowing acceleration to surpass loss. Additionally, we demonstrate that even with the same chorus diffusion coefficients and the same low‐energy boundary condition, the flux of ∼500‐keV to 1‐MeV electrons increased when starting with a hard spectrum but decreased for a soft initial spectrum. This suggests that initial energy gradients in the phase space density were important to determine whether >500‐keV electrons were enhanced due to chorus wave acceleration.
Decadal Stabilization of Soil Inorganic Nitrogen as a Benchmark for Global Land Models
Authors: Wei Ning , Cui Erqian , Huang Kun , Du Zhenggang , Zhou Jian , Xu Xiaoni , Wang Jing , Yan Liming , Xia Jianyang
Published: April 2019

Global land models are now routinely incorporating the nitrogen (N) cycle into simulations, but the identification of its benchmarks has lagged behind. An important variable in these models is the soil inorganic N (SIN) which is the resultant of different input and output N processes. However, whether and how the SIN pool and its spatiotemporal variation can be used as benchmarks for models remains unclear. Here we first constructed a database of measured SIN at 756 sites from 1980 to 2010 across China, one of the regions that has been experiencing the highest external N input. Although there was great spatial variability of the measured SIN pool, no significant changes were detected across China during 1980–2010 based on a bootstrapping approach. The medians of the measured SIN across China were 63, 70, and 65 mg/kg during the 1980s, 1990s, and 2000s, respectively. Then, we used the regional SIN database to evaluate two versions of the Community Land Model (i.e., CLM4.5 and CLM5.0). In comparison with the observation (median 75 mg/kg) at grid‐cell scale, both CLM4.5 (median 0.70 mg/kg) and CLM5.0 (median 0.79 mg/kg) underestimated the SIN pools across China. Although the drivers of such modeling biases are difficult to identify at the current stage, improved representations of both input and output processes of the SIN pool in the models are highly recommended. These findings suggest that a decadal stabilization of the SIN pool in terrestrial ecosystems and the spatial distribution of the SIN pool may be a useful benchmark for global biogeochemical models.
Enhancing high harmonic generation by the global optimization of a two-color chirped laser field
Authors: Mofared Mohammad , Irani Elnaz , Sadighi-Bonabi Rasoul
Published: April 2019

Enhanced high harmonics are generated by local and global optimization approaches to achieve a supercontinuum spectrum.
Juggling bubbles in square capillaries: an experimental proof of non-pairwise bubble interactions
Authors: Ginot Gaël , Höhler Reinhard , Mariot Sandrine , Kraynik Andy , Drenckhan Wiebke
Published: April 2019

Volume conservation leads to “many-body” interactions between bubbles/drops in foams/emulsions: there is no unique relation between displacement and force at a given contact.
Controlled release from PCL–alginate microspheres via secondary encapsulation using GelMA/HAMA hydrogel scaffolds
Authors: Caballero Aguilar Lilith M. , Kapsa Robert M. , O'Connell Cathal D. , McArthur Sally L. , Stoddart Paul R. , Moulton Simon E.
Published: April 2019

The release profile of a bioactive-model molecule from alginate/PCL–alginate microspheres resulted depending on the degree of functionalization and the crosslink of 3-dimensional scaffolds.
General scaling relations and prediction of transition state energies in CHA/AlPO-34-structured zeolite catalysis related to the methanol-to-olefins conversion
Authors: Wang Chuan-Ming , Wang Yang-Dong , Xie Zai-Ku
Published: April 2019

Scaling relations of transition state (TS) energies with the acid strength were established. The inherent scaling relations and the acidity sensitivity dependence on charge variation enable fast prediction of TS energies in zeolite catalysis.
Enhancing the stability and efficiency of the anammox process in plug-flow integrated fixed-film activated sludge (IFAS) reactors through alternating anoxic/aerobic (A3) conditions
Authors: Liu Chao , Liu Wenlong , Wu Lei , Peng Yongzhen
Published: April 2019

The breakthrough of this study was the development of plug-flow integrated fixed-film activated sludge (IFAS) reactors operated with alternating anoxic/aerobic (A3) conditions for enhanced anammox processes.
Grifola frondosapolysaccharides ameliorate lipid metabolic disorders and gut microbiota dysbiosis in high-fat diet fed rats
Authors: Li Lu , Guo Wei-Ling , Zhang Wen , Xu Jia-Xin , Qian Min , Bai Wei-Dong , Zhang Yan-Yan , Rao Ping-Fan , Ni Li , Lv Xu-Cong
Published: April 2019

G. frondosapolysaccharides have the potential to ameliorate lipid metabolic disorders in part through modulating gut microbiota and mRNA expression of genes involved in hepatic lipid and cholesterol metabolism.
Decarboxylative acylation of N-free indoles enabled by a catalytic amount of copper catalyst and liquid-assisted grinding
Authors: Yu Jingbo , Zhang Chao , Yang Xinjie , Su Weike
Published: April 2019

A mechanochemically Cu(ii)-catalyzed decarboxylative acylation of N-free indoles with O2 as a terminal oxidant was developed for the mild synthesis of 3-acylindoles.
Understanding the Li-ion storage mechanism in a carbon composited zinc sulfide electrode
Authors: Tian Guiying , Zhao Zijian , Sarapulova Angelina , Das Chittaranjan , Zhu Lihua , Liu Suya , Missiul Aleksandr , Welter Edmund , Maibach Julia , Dsoke Sonia
Published: April 2019

The Li+ storage mechanism in a carbon composited zinc sulfide as an enhanced conversion-alloying anode material for Li+ ion batteries is studied by in situ methods. Further, it is found that the (de)lithiation processes are affected by a low charge transfer resistance, and the coated carbon can effectively improve the long-term cycling stability.
A dually prewetted membrane for continuous filtration of water-in-light oil, oil-in-water, and water-in-heavy oil multiphase emulsion mixtures
Authors: Cao Guoliang , Wang Yonggui , Wang Chengyu , Ho Shih-Hsin
Published: April 2019

An underwater superoleophobic and underoil superhydrophobic dually prewetted membrane can be used in various continuous separation processes of water-in-light oil, oil-in-water, and water-in-heavy oil multiphase emulsion mixtures.
Robust superhydrophobic dual layer nanofibrous composite membranes with a hierarchically structured amorphous polypropylene skin for membrane distillation
Authors: Deng Li , Li Peiyun , Liu Kang , Wang Xuefen , Hsiao Benjamin S.
Published: April 2019

A novel superhydrophobic aPP/PVDF dual layer composite membrane consisting of a hierarchically structured selective skin from aPP and a PVDF nanofibrous support for efficient desalination by DCMD.
A selective fluorescent sensor for cysteine detection with potential as a white light emitting fluorophore in living cell imaging
Authors: Yang Yu-Shun , Yuan Zeng-Hui , Zhang Xu-Ping , Xu Jian-Fei , Lv Peng-Cheng , Zhu Hai-Liang
Published: April 2019

A novel fluorescent sensor CysW-1 was introduced for cysteine detection via the cleavage reaction of two fluorophores. Then a relatively steady and practical white light emitting system was successfully generated. The biocompatibility ensured the living cell imaging and further pre-clinical applications.
Object detection for panoramic images based on MS‐RPN structure in traffic road scenes
Authors: Tong Guofeng , Chen Huairong , Li Yong , Du Xiance , Zhang Qingchun
Published: April 2019

The objection detection of panoramic image is the key part of street view, intelligent transportation, automatic driving and other technologies. Due to the shortcomings of existing algorithms in detecting panoramic images, firstly a high‐resolution panoramic image dataset is introduced, then the multi‐scale feature pyramid networks (MS‐RPN) structure is proposed and a new network with Sim‐Inception module is designed. The network can extract different scales of objects from different feature layers, so that the small object in the image can also be accurately detected. Finally, the entire detection network is trained by using the dataset constructed in this study. Meanwhile, the ROIPool is replaced by ROIAlign and the loss function is adjusted according to the network structure. The experimental results show that the detection performance on the panoramic dataset is significantly improved by authors’ proposed algorithm, which is better than other deep learning algorithms, especially for small object in the image.
Low voltage ride through capability enhancement in a grid‐connected wind/fuel cell hybrid system via combined feed‐forward and fuzzy logic control
Authors: Roy Amit Kumar , Basak Prasenjit , Biswal Gyan Ranjan
Published: April 2019

Fault ride through (FRT) capability is an essential practice as per the present grid code demands for grid‐connected renewable energy‐based distributed energy resources. Studies on FRT capability for grid‐connected hybrid systems are rarely found. This study considers a wind energy conversion system and a fuel cell system interconnected at a common dc bus. It proposes a new feed‐forward‐based FRT control scheme for the inverter control where new current references in dq‐axis frame are derived by tracking the positive sequence power. The newly derived references are fed forward to the input of the current regulator of the voltage source inverter. Second, fuzzy logic‐based current controllers are suggested to improve the tracking capability of the current references in the inverter control scheme so as to enhance the FRT capability of the hybrid system as a whole. The proposed feed‐forward‐fuzzy control scheme for achieving an enhanced FRT capability is compared with the conventional dq current control and feed‐forward FRT control for various grid voltage sag tests, where the performance of the combined feed‐forward‐fuzzy control is found better. The validation of the proposed FRT control scheme is performed in MATLAB‐Simulink environment.
Analysis of real‐world implementation challenges of chipless RFID tag
Authors: Shrestha Sika , Karmakar Nemai Chandra
Published: April 2019

Radio frequency identification (RFID) tags are highly sensitive to material contents of the tagged objects, especially with liquids and metals. The presence of an attached object on the tag can be detrimental for tagID detection. In this study, the RF performance of chipless RFID tag placed on different commercial objects for identification purpose is comprehensively analysed. Probable solutions are proposed for observed issues to make the chipless RFID tags readable on various items such as non‐conductive objects, liquid containers and metal items. The misalignment between the reader antenna and the tag is another issue during the commercial implementation of chipless RFID system. A tri‐planar positioning of the tag has been verified as an appropriate solution in this study. The chipless tag has the potential to read stacked pallets and boxes with liquid/solid contents in warehouse scenarios using the proposed solutions.
Cavity model analysis of differential dual‐polarised annular‐ring patch antenna
Authors: Xu Guanghui , Peng Hong‐Li , Zhang Yaoping , Yin Wen‐Yan , Mao Jun‐Fa
Published: April 2019

The four‐port cavity model is presented to study a differential dual‐polarised annular‐ring patch antenna operating at higher order mode TM12. Acceptable agreements among calculated, simulated, and measured impedances and radiation patterns are obtained. Theoretical analysis shows that the differential port‐to‐port coupling impedance is zero, and its isolation is theoretically infinite. The differential input impedance is about four times of the single‐ended input impedance at the resonant frequency of higher order mode TM12. The differential operation can suppress the adjacent modes TM02 and TM22 near the operating mode TM12 and lead to a more symmetrical E‐plane radiation pattern and lower cross polarisation level.
Channel characterisation in rural railway environment at 28 GHz
Authors: Wang Longhe , Ai Bo , He Danping , Yi Haofan , Zhong Zhangdui , Kim Junhyeong
Published: April 2019

Nowadays, rail traffic is expected to evolve into a new era of ‘smart rail mobility’, where trains, infrastructure, travellers and goods will be increasingly interconnected. Railway communications are required to support various high‐data‐rate applications, the communication system should be carefully designed, which makes railway scenario becomes a more and more important communication scenario. In this study, the channel characteristics are analysed for rural railway at 28 GHz. Four different deployments are considered via calibrated ray‐tracing simulations in the target environment. The large‐scale parameters of the mmWave channel, including the path loss, root‐mean‐square delay spread, Rician K‐factor, angular spreads and cross‐polarisation ratio are explored. The statistical properties, decorrelation distance and cross‐correlations are analysed as well. The studied channel characteristics can be used to support the link level and system level design of the communication system in the similar environment.
HANKEL‐EM‐SVD: a hybrid data dropout estimation technique for high voltage partial discharge signals
Authors: Govindarajan Suganya , Subbaiah Jayalalitha , Krithivasan Kannan , Natarajan Muthukumar
Published: April 2019

Partial discharge (PD) measurement and characterisation is the most effective method to assess the insulation conditions of equipment for its diagnosis. A significant challenge in this area is PD denoising. Despite recent advancements in denoising algorithms, data drops out because of inappropriate threshold selection during denoising. Processing PD signals with missing data leads to an inaccurate assessment of the insulation conditions, indicating recovering such missed data is a potential research scope under the moonlight. This study addresses the issues of recovering such data dropouts by considering the PD data vector matrix as a low‐rank matrix that needs completion by Hankel‐matrix decomposition methods. After finding the probabilistic estimate of the missing values using an expectation maximisation algorithm, singular‐value decomposition is used to find the actual missing values by soft‐thresholding the singular values of the matrix. After testing this technique on simulated PD data, it is implemented to test SASTRA‐High‐Voltage Laboratory data, showing root mean square error (RMSE) 0.77% and mean absolute error 0.84%. The efficiency of this technique is confirmed when tested with large‐sized noise free PD data of 36 samples from the Laboratory of BOLOGNA University (with RMSE varying from 0.15 to 0.31% and mean absolute error varying from 0.29 to 0.6%).
Design route towards a PM machine for rotorcraft environments
Authors: North Dominic , Yon Jason , Baker James , Booker Julian , Mellor Phil
Published: April 2019

This paper discusses the design route followed in the development of a permanent magnet (PM) machine for electrical power generation on board a rotorcraft (helicopter). The focus of the machine design is to optimise system power density, efficiency, and robustness – all of which are crucial considerations in aerospace applications. A matrix of designs was created consisting of two stators with different winding conductors – copper and aluminium – and three rotors, each using different containment sleeve materials. These include two semi‐permeable metallic sleeves, which act to decrease the effective air gap. Combinations of the different materials will yield different system‐level power densities and efficiencies. Here, all the designs are presented along with the initial test results for the baseline machine combination validating the design predictions.
Multilayer air gap winding designs for electric machines: theory, design, and characterisation
Authors: Borchardt Norman , Kasper Roland , Sauerhering Jörg , Heinemann Wolfgang , Foster Kimberly L.
Published: April 2019

Here, the authors present a magnetic circuit design with a multilayer air gap winding. This design provides a new degree of freedom in the design process. The approach is based on a single layer air gap winding, which demonstrates the ability to scale, permitting application in small and large electric machines. A meandering structure with coils arranged parallel to the rotation axis are mounted in several layers on a slotless magnetic core. The authors consider a fixed ohmic power loss boundary condition to compare this approach with an existing validated machine design. Machine current is reduced with each winding layer, while self‐inductance and induced voltage are increased. Since the air gap height is increased with every additional layer, the useable magnetic flux density decreases. Accordingly, an utilisable range in which optimal torque output is obtained can be described analytically. The authors provide comparison between a single‐layer winding design, which achieves the global optimum torque, and a four‐layer winding design, which gives a 16‐fold increase in the phase self‐inductance. Additional thermal simulations prove that the multilayer design give the same ohmic power losses as the single layer design, without having any thermal issues and hot spots.
Control and operation of the MMC‐based drive with reduced capacitor voltage fluctuations
Authors: Antonio Espinoza Bolaños Mauricio , Díaz Matías , Donoso Felipe , Letelier Arturo , Cárdenas Roberto
Published: April 2019

The modular multilevel converter (MMC) has emerged as a suitable topology for high power drive applications. However, the voltage fluctuations of its floating capacitors increase the control complexity of the converter. In this study, the MMC dc‐port voltage is manipulated to regulate the amplitude of these fluctuations to a constant value during the whole frequency range. The proposed approach has several advantages when compared with the conventional ones since it minimises the voltage fluctuation in the capacitor cells. Additionally, it decreases the common‐mode voltage at low frequencies and the capacitor rms current, increasing their expected lifespan and reducing the winding insulation damages and the leakage currents in the bearing of the machine. The effectiveness of the proposed control strategy is validated with a laboratory‐based prototype composed of 18 power cells, feeding a vector‐controlled induction machine.
Sensorless control of PMSM using an adaptively tuned SCKF
Authors: Gopinath Gulur Raghavendra , Shyama Prasad Das
Published: April 2019

This study reports the application of an adaptively tuned square‐root Cubature Kalman filter (SCKF) for the speed and position estimation of a permanent magnet synchronous motor (PMSM) drive. The proposed estimator is observed to exhibit improved noise rejection characteristics as compared to the hitherto widely applied extended Kalman filter (EKF) observer. A third degree spherical–radial cubature rule is used in the Cubature Kalman filter (CKF) to numerically compute the multivariate moment integrals of the general Bayesian estimation equation. CKF is a non‐linear filter which avoids linearisation and the associated errors. The realisation of CKF using the square‐root algorithm results in numerical stability, as with the realisation of EKF using the square‐root algorithm. Simulation results are presented for a three‐phase inverter‐fed PMSM, along with the experimental results. The estimator and the control algorithms are realised on the MATLAB real‐time environment, interfaced with the hardware using the National Instruments data acquisition system NI PCI‐6221.
Modular multilevel converter with DHB energy‐balancing channels for medium‐voltage adjustable‐speed drives
Authors: Diab Mohamed S. , Holliday Derrick , Massoud Ahmed M. , Ahmed Shehab , Williams Barry W.
Published: April 2019

This paper presents a modular multilevel converter (MMC) configuration that utilises energy exchange between sub‐modules (SMs) of upper and lower arms, for energy rebalancing. The configuration is applicable to medium‐voltage high‐power variable‐speed drives with any number of motor phases, where the traditional MMC topology experiences challenging shortcomings. With the out‐of‐phase alternation of the fundamental ripple power in upper and lower arms, the proposed MMC configuration decouples this ripple power by employing dual half‐bridge modules linking opposite SMs in upper and lower arms of the same MMC‐leg. This counter‐balances arm ripple‐power through bidirectional power transfer between opposite SMs, resulting in a reduction in the SM capacitance and the MMC system stored energy. The proposed MMC configuration solves the problem of wide SM capacitor voltage fluctuation, especially at low operating frequencies, where the SM capacitor voltage ripple profile is almost constant, independent of the operating frequency. Therefore, the configuration is able to drive multi‐megawatt machines from stand‐still to the rated speed, at rated torque. The operation of the proposed converter topology is elucidated in detail, and its effectiveness is verified through simulation and experimentation.
Hybrid PV/battery‐storage unit for residential applications
Authors: Bagheri‐Farahbakhsh Mina , Cross Andrew , Strickland Dani , Morris Paul , Martin Trevor , Lakin Tony
Published: April 2019

Under their ‘Gone Green’ deployment scenario, National Grid forecast that energy generated from photovoltaics (PV) in the UK is expected to rise from 2 to 15 GW over the next 20 years. This is being driven by the UK's legal obligations around installing renewable energy sources and cutting greenhouse gases, the rising cost of energy and concerns around the security of supply. Power electronic converters are a key enabling technology for PV and other low‐carbon technologies (LCTs). However, the use of LCTs can result in problems for the electrical distribution network such as supply voltage distortion and over‐voltages, which threaten to limit or delay their uptake. The project described here is investigating the use of GaN‐based converters in a hybrid PV/battery‐storage unit for residential applications. The potential for MHz operation of GaN offers smaller, lighter, more efficient, and lower cost converters compared with existing silicon‐based units and their deployment could lead to an increase in the installed LCT capacity on the network.
Power converter junction temperature measurement using infra‐red sensors
Authors: Smith Christopher J. , Zappalá Donatella , Crabtree Christopher J. , Lapiedra Justo , Mulholland Brian
Published: April 2019

Studies demonstrate that the power converter has one of the highest failure rates in a wind turbine, with a key failure driver being the power module junction temperature (Tj). This paper details an experimental setup for simplified emulation of wind turbine conditions on a power converter with infra‐red sensing of IGBT Tj. Results are compared to previous simulation work for a PMSG wind turbine, with the same trend of increasing mean Tj with wind speed found, and the need to use an equivalent generator reactance in highlighted. A commercial‐scale prototype for more accurate wind turbine converter emulation is also detailed.
Common mode voltage elimination in dual‐inverter‐fed six‐phase open‐end winding PMSM drives with a single DC supply
Authors: Mekasser Mounir , Gao Qiang , Xu Cai
Published: April 2019

This paper proposes a space vector pulse width modulation (SVPWM) technique to eliminate common mode voltage (CMV) and common mode current for dual‐inverter six‐phase open‐end winding PMSM motor drive fed from a single DC supply. In such a topology, it is mandatory to eliminate the CMV created by the switching PWM of dual‐inverter in order to arrest the circulation of common mode current. Based on vector space decomposition (VSD) theory, the switching states’ combinations which do not produce CMV are identified and a space vector pattern with zero CMV is obtained. Proper space vectors are chosen to synthesise the reference voltage, where the resultant reference voltage is decomposed into two components controlled by two modulators independently. The proposed SVPWM technique is compared with the conventional control by simulation in Matlab/Simulink. The performance of the proposed SVPWM technique is evaluated, and the results show the CMV is successfully eliminated.
Feasibility study of embedded FBG thermal sensing use for monitoring electrical fault‐induced thermal excitation in random wound coils
Authors: Mohammed Anees , Djurović Siniša
Published: April 2019

This paper reports an experimental feasibility study of the potential for using Fibre Bragg Grating (FBG) thermal sensing technology for electrical fault detection in random wound coils. The study is performed on prototype test coils housed in a purpose built steel core section. The FBG thermal sensors are embedded between copper conductors in multiple positions within the coil structure and in close proximity of the known hot spots of interest. The examined coils are designed to enable emulation of hot spots representative of those that would be expected at the outset of winding fault events. A series of experiments were separately conducted in order to characterise the potential of coil internal thermal stress monitoring to provide recognition of a developing winding fault. To this end, winding fault scenarios with different severity levels of inter‐turn fault are experimentally examined. The reported findings demonstrate the potential of the proposed in‐situ thermal sensing scheme to enable monitoring and recognition of coil internal thermal stress induced at various stages of emulated electrical fault.
Linear consequent pole Halbach array flux reversal machine
Authors: Raihan Mohammad Abdul Hakim , Baker Nick , Smith Kristopher , Almoraya Ahmed
Published: April 2019

This paper presents a linear variable reluctance permanent magnet (LVRPM) machine where the armature winding and inset Halbach array permanent magnets (PMs) are mounted on E‐core stators. The Halbach array consists of a vertically magnetised PM pole and a salient ferromagnetic iron pole (split tooth) sandwiched between two horizontal PMs. The translator consists solely of laminations with salient iron poles. As a variable reluctance machine, it exhibits inherent magnetic gearing and a higher force and power density than the conventional synchronous PM machines. Finite element analysis (FEA) has been used to investigate the effect of machine parameters. The logical development of the LVRPM from the more conventional Vernier Hybrid machine is presented, including a near 50% reduction in magnetic flux leakage and a higher flux per unit magnet mass.
Transient skin effect in power electronic applications
Authors: Donaghy‐Spargo Christopher , Horsfall Alton
Published: April 2019

This study describes transient electromagnetic phenomena in electrical conductors that are connected to modern power electronic circuits and therefore subjected to current controlled pulses with fast rise times and high peak current ratings. Electromagnetic field diffusion is discussed and a brief review of alternating current skin effect phenomena is presented before it is generalised to transient regimes of operation. It is shown that the magnetic field diffuses into the conductor from the outside on the initiation of a current pulse and therefore the axial current density distribution inside the conductor changes with time under a transient current due to the well‐known electromagnetic relations – the current begins at the conductor surface and diffuses inwards. The implications of such behaviour are briefly discussed in the context of modern power electronics and its applications.
Harmonics and unbalanced load compensation by a modular multilevel cascaded converter active power conditioner
Authors: Huang Han , Oghorada O.J.K. , Zhang Li , Chong B.V.P.
Published: April 2019

This paper presents a novel control scheme for a modular multilevel cascaded converter (MMCC) functioning as an active power conditioner (APC) to control the reactive power, eliminate the current harmonics, and compensate unbalanced load current simultaneously. This combines a modified predictive current controller with the inter‐cluster and intra‐cluster voltage balance control for MMCC sub‐module capacitors. Simulation studies of this MMCC‐APC for a power network containing both an unbalanced thyristor controlled rectifier and a reactive load are performed and results verifying its performance under varying degrees of load current distortion measured by THD levels are presented.
Multi‐functional grid‐connected inverter with enhanced disturbance rejection capability
Authors: Sun Guangyu , Li Yongli , Jin Wei , Bu Lizhi , Chen Xiaolong
Published: April 2019

Apart from the basic renewable generation function, the multi‐functional grid‐connected inverter (MFGCI) derived from traditional grid‐connected inverter could provide ancillary power quality enhancement functions for the interfaced grid. However, with multiple functions integrated into one control system, the control scheme of MFGCI would become inevitably more complicated and vulnerable to the disturbance in distribution networks. Here, a control scheme of MFGCI for rejecting both the steady‐state and dynamic‐state disturbance is designed. The proposed control scheme includes an inner loop controller and an improved reference current generation algorithm, which constitutes an overall MFGCI control scheme. To reject the steady‐state disturbance which would distort the output current of MFGCI, the inner loop controller by combining the linear adaptive disturbance rejection controller (LADRC) and repetitive controller (RC) is designed. While for the dynamic‐state disturbance which would amplify the output current of MFGCI or even destroy the stability of the system, an improved reference current generation algorithm with enhanced dynamic disturbance rejection capability is proposed. The proposed MFGCI could provide overall improvements in both dynamic‐ and steady‐state disturbance rejection capability. Finally, some experiments are conducted to verify the superiority of the proposed MFGCI.
Permanent magnet synchronous machine stator windings fault detection by Hilbert–Huang transform
Authors: Alvarez‐Gonzalez Fernando , Griffo Antonio , Wang Bo
Published: April 2019

The Hilbert–Huang transform (HHT) is a time‐frequency signal analysis method based on empirical mode decomposition and the Hilbert transform. It is well suited for reliable fault detection since it is unaffected by transient conditions which might cause false alarms. The method has been demonstrated in recent years for bearing fault detection of induction machines (IM). This study explores the possibility of applying the technique to the detection of stator short‐circuit faults in permanent magnet synchronous machine (PMSM). A method based on the online statistical analysis of the instantaneous frequency calculated by the HHT is proposed and demonstrated through real‐time hardware‐in‐the‐loop simulation and experimental results.
Cold water immersion improves recovery of sprint speed following a simulated tournament
Authors: Leeder Jonathan D. C. , Godfrey Matthew , Gibbon Daniel , Gaze David , Davison Gareth W. , Van Someren Ken A. , Howatson Glyn
Published: April 2019

It is a common requirement in tournament scenarios for athletes to compete multiple times in a relatively short time period, with insufficient recovery time not allowing full restoration of physical performance. This study aimed to develop a greater understanding of the physiological stress experienced by athletes in a tournament scenario, and how a commonly used recovery strategy, cold water immersion (CWI), might influence these markers. Twenty‐one trained male games players (age 19 ± 2; body mass 78.0 ± 8.8 kg) were randomised into a CWI group (n = 11) or a control group (n = 10). To simulate a tournament, participants completed the Loughborough Intermittent Shuttle Test (LIST) on three occasions in five days. Recovery was assessed at specific time points using markers of sprint performance, muscle function, muscle soreness and biochemical markers of damage (creatine kinase, CK), inflammation (IL‐6 and C‐Reactive Protein) and oxidative stress (lipid hydroperoxides and activity of 6 lipid‐soluble antioxidants). The simulated tournament was associated with perturbations in some, but not all, markers of physiological stress and recovery. Cold water immersion was associated with improved recovery of sprint speed 24 h after the final LIST (ES = 0.83 ± 0.59; p = .034) and attenuated the efflux of CK pre‐ and post‐LIST 3 (p < .01). The tournament scenario resulted in an escalation of physiological stress that, in the main, cold water immersion was ineffective at managing. These data suggest that CWI is not harmful, and provides limited benefits in attenuating the deleterious effects experienced during tournament scenarios.
Association of electrocardiographic left and right ventricular hypertrophy with physical fitness of military males: The CHIEF study
Authors: Chao Wei‐Hsiung , Su Fang‐Ying , Lin Felicia , Yu Yun‐Shun , Lin Gen‐Min
Published: April 2019

AIM: To investigate the association of electrocardiographic (ECG) left and/or right ventricular hypertrophy (LVH and RVH) with physical fitness of military males.

METHODS: We used a military cohort of 2587 males, who were on average 29.1 years of age, from the cardiorespiratory fitness and hospitalization events in armed forces (CHIEF) study in Taiwan for the analysis. Isolated ECG‐LVH (n = 779) was diagnosed by either the Sokolow‐Lyon or Cornell voltage criteria. Isolated ECG‐RVH (n = 234) was defined by either the Sokolow‐Lyon or Myers et al. voltage criteria. Combined ECG‐LVH/RVH (n = 140) was defined as those who met the voltage criteria for both LVH and RVH. The other ECGs were defined as unaffected (n = 1434). Physical fitness was evaluated by the upper and lower 16% exercise performance (beyond 1‐standard deviation) in 3000‐meter run, 2‐minute sit‐ups, and 2‐minute push‐ups. All procedures were standardized and monitored by unified computerized scoring systems. A multiple logistic regression was used to determine the relationship.

RESULTS: Compared with unaffected participants, those with an isolated ECG‐LVH were tended to have a better 3000‐meter run performance (odds ratio (OR) and 95% confidence intervals: 1.22 [0.99–1.50], p‐value = 0.064) after adjusting for age, service specialty, body mass index, mean blood pressure, smoking status, alcohol intake, hemoglobin level, and exercise frequency. By contrast, those with an isolated ECG‐RVH were tended to have a worse 2‐minute sit‐up performance (OR: 1.46 [0.99–2.16], p‐value = 0.054).

CONCLUSION: Military males with ECG‐LVH and/or ECG‐RVH compared to unaffected participants may have diverse exercise performances. However, these observations narrowly failed to reach statistical significance.