bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improving Ag‐TiO2nanocomposites’ current density by TiCl4 pretreated on FTO glass for dye‐sensitised solar cells
Authors: Lokman Muhammad Quisar , Shaban Suraya , Shafie Suhaidi , Ahmad Fauzan , Yahaya Hafizal , Rosnan Rizuan Mohd , Ibrahim Mohd Adib 
Published: March 2021

AbstractTitanium tetrachloride (TiCl4) pretreatment on the fluorine‐doped tin oxide (FTO) is one of the alternative techniques to enhance short‐circuit current density (Jsc) and efficiency of dye‐sensitised solar cells (DSSC) by improving the inter‐particle bonding between FTO grain and nanoporous titanium dioxide (TiO2). The present study investigbrkates the effect of TiCl4 pretreatment on the surface of FTO glass to enhance the Jsc and efficiency of silver‐titanium dioxide (Ag‐TiO2) nanocomposites. The pretreatment process was prepared by immersing FTO glass into TiCl4 solution at 70°C for 30 min, and then sintered at 500°C for 30 min. Morphological and elemental characteristics were done to observe the structure and composition of pretreatment on the FTO glass. The results showed that the Ag‐TiO2 with TiCl4 pretreatment achieved high efficiency of 7.27% with Jsc of 18.95 mA/cm2. The proposed method shows that the pretreatment can improve the efficiency by improving the inter‐particle bonding between nanoporous TiO2 and FTO grain, which can enhance the electron transfer. Also, the presence of Ag in the nanocomposites as a solar concentrator can increase the light absorption by TiO2 nanoparticles and also increase the DSSC efficiency.
Generation of second harmonic component of fault current in a doubly‐fed induction generator and mitigation measures for transformer protection
Authors: Zheng Tao , Yan Jingxian , Li Jing , Wang Xingguo , Zhao Hongcheng , Wang Sirui 
Published: March 2021

AbstractThe transient characteristics of short‐circuit current (SCC) in doubly‐fed induction generator (DFIG) are quite different from the widely researched conventional synchronous machines. However, the second harmonic characteristics of SCC that impact the reliability of the transformer protection have not been accurately analysed. This paper presents the generation mechanism of second harmonic SCC in DFIG by deducing the dynamic response of rotor‐side converter, with particular attention to the influences of the voltage drop, harmonic component of stator voltage, frequency coupling, and deviation of the phase‐locked loop. When grid fault occurs, the terminal voltage sag leads to fluctuations in the active power, then the response of converter to power fluctuation and the frequency coupling leads to the second harmonic current in the abc reference frame. And the second harmonic current injected into the grid leads to fluctuations in the voltage disturbance term and deviation of the phase‐locked loop, which, in turn, affects the second harmonic current. Based on the analysis, the mitigation measures for the second harmonic current are proposed. Simulations are implemented to verify the theoretical analysis.
Inverter harmonic perturbations rejection in renewable energy conversion systems applying a super‐twisting algorithm
Authors: Memije Daniel , Carranza Oscar , Rodríguez Jaime J. , Ortega Rubén , Peralta Edgar 
Published: March 2021

AbstractGrid background and dead‐time harmonic perturbations pose challenges in maintaining power quality and stability in the grid integration of renewable energy conversion systems. Therefore, a super‐twisting algorithm with the ability to reject harmonic perturbations on three‐phase grid‐tied inverters is proposed. The algorithm design is related to dead‐time and grid background harmonics so that robust performance is achieved under these perturbations. To highlight the advantages of the proposed algorithm, it is compared against proportional‐integral (PI) control in several dead‐time and grid background harmonic sweeps. The maximum inverter current distortion obtained with PI control in simulation is 15.53%. However, by using the proposed algorithm instead, the maximum current distortion is reduced to 1.8%. Dead‐time is experimentally swept by using a permanent magnet motor as a harmonic‐free grid. Experimental results of grid background harmonics are obtained by injecting reactive energy into a grid with 2.19% voltage distortion. When PI control is used in the experimental setup, the maximum inverter current distortion obtained is 11.4%. However, with the proposed algorithm, the maximum current distortion is reduced to 1.5%, which complies with the standard IEEE 1547‐2018.
Non stationary‐ARMA flicker model for squirrel cage induction generators based wind farms
Authors: Samet Haidar , Ketabipour Saeedeh , Bagheri Ali Asghar 
Published: March 2021

AbstractTime varying nature of the wind power is studied previously considering different time intervals from seconds to days. However for power quality problems such as flicker, a model which considers the extremely fast variations is essential. Here by using large number of actual records, a time‐varying model is proposed which considers the extremely short‐time variations of wind active and reactive powers. The wind farm is modelled as a current source with time varying amplitude and phase which change every 0.01 s. Autoregressive moving‐average (ARMA) models are utilized to model the variations and ARMA coefficients are calculated for every record. Same to the actual behaviour, the proposed model is non‐stationary as the ARMA order and coefficients are different at every run of the model. The proposed model is confirmed through utilizing several applications which need the power time series with extremely short sampling intervals. The following studies are performed by using the actual data and then the proposed model: power spectral density of active and reactive power variations, instantaneous flicker, short term flicker (Pst), estimating the Pst using the maximum value of the instantaneous flicker, estimation of cumulative Pst for multiple wind turbines, and the impact of SVC on flicker mitigation.
Export cable rating optimisation by wind power ramp and thermal risk estimation
Authors: Hernandez Colin Maria A. , Dix Justin , Pilgrim James 
Published: March 2021

AbstractThis paper demonstrates the impact of using realistic wind power generation profiles, time‐varying ocean bottom temperatures and hypothetical wind farm over‐planting scenarios on export cable capacity optimisation. Given the inherent risk in over‐planting, a novel hour ahead thermal risk estimation method was developed to foresee and mitigate cable temperature exceedance, employing a preventive curtailment. Two offshore wind farm locations L1(North‐west European Shelf) and L2(Australian Shelf) have been chosen for testing but utilising real wind and ocean bottom temperature data. These simulated results demonstrate a 10% rating increment over the static rating in L1 resulted in a 13% increment in the amount of energy delivered over a year (MWh/year) without any risk or instances of thermal overheating. Similarly, a 9.8% rating increment in L2 resulted in a 13.6% increment in annual energy transmission (MWh/year). The financial increment for both over‐planting scenarios was approximately 9 million/year for the studied cases.
Current indicator based fault detection algorithm for identification of faulty string in solar PV system
Authors: Chandrasekharan Sowthily , Subramaniam Senthil Kumar , Natarajan Babu 
Published: March 2021

AbstractThe maximum power generation in the solar photovoltaic (PV) array is reduced due to the abnormal conditions such as module mismatch, string faults and damage of the PV modules, which reduces the efficiency and reliability of the system. Conventional protection devices fail to detect the faults, which leads to protection issues and fire threats in the PV plants. This paper proposes a new fault detection algorithm to identify the faults in the PV array and the PV string. A simple analysis is developed for fault detection under different fault conditions, such as line–line (L‐L) fault, line–ground (L‐G) fault and short‐circuit fault with multiple strings, and the values of their current indicator and threshold are predetermined. Based on these values, the proposed fault detection algorithm identifies the fault in the PV array and the PV string, with a reduced number of current sensing devices. The effectiveness of the proposed algorithm is tested and verified through MATLAB simulation and experimentation under various operating conditions of the solar PV plant.
Frequency control in hybrid distributed power systems via type‐2 fuzzy PID controller
Authors: Kumar Khadanga Rajendra , Kumar Amit , Panda Sidhartha 
Published: March 2021

AbstractIn this research article, a novel approach is proposed by considering a modified equilibrium optimization (MEO) algorithm based “interval type‐2 fuzzy proportional integral derivative (IT2FPID) controller” for the load frequency control of the multi‐area hybrid power system. The performance of the modified algorithm is tested by comparing it with the standard EO algorithm considering various standard benchmark test functions. Further, the efficacy of the MEO algorithm is tried by planning an IT2FPID controller for frequency regulation of the said hybrid system. The supremacy of the MEO‐based IT2FPID controller is introduced by comparing its outcomes with MEO‐based T1FPID structure, MEO‐based conventional PID and EO‐based PID controller techniques. It is observed that the MEO‐based IT2FPID controller is more effective compared to others.
A modular multilevel DC‐DC converter with self‐energy equalization for DC grids
Authors: Elserougi Ahmed , Abdelsalam Ibrahim , Massoud Ahmed , Ahmed Shehab 
Published: March 2021

AbstractMedium‐/High Voltage DC grids are interesting for the integration of renewable energy sources. DC‐DC conversion systems are highly needed for the development of DC grids. Recently, Modular Multilevel Converter (MMC) is the most promising technology for medium‐/high‐voltage applications, but employing the conventional MMC with DC output voltage leads to diversion in the Submodule (SM) capacitor voltages, that is energy drift. This paper proposes a modified modular multilevel DC‐DC converter with self‐energy equalization, which ensures successful DC‐DC conversion with balanced capacitors voltages. In the modified topology, clamping Insulated Gate Bipolar Transistors (IGBTs) are employed in each arm to enable parallel‐connection of the capacitors in the same arm. During the operation (equalization period), the parallel‐connected upper capacitors are connected to the parallel‐connected lower capacitors in each leg through a small limiting inductor to transfer energy between the arms to ensure balanced capacitor voltages. The proposed configuration, along with the operational concepts, mathematical analysis, and design, are presented. Finally, simulation and experimental results are presented for validation.
Coordinated flexible energy and self‐healing management according to the multi‐agent system‐based restoration scheme in active distribution network
Authors: Bagherzadeh Leila , Shayeghi Hossein , Pirouzi Sasan , Shafie‐khah Miadreza , Catalão João P. S. 
Published: March 2021

AbstractThis study presents the optimal model of the coordinated flexible energy and self‐healing management (C‐FE&SH‐M) in the active distribution network (ADN) including renewable energy sources (RESs), electric vehicles (EVs) and demand response program (DRP).The flexible energy management (FEM) is extracted using coordination between the RESs, EVs and DRP. The self‐healing method (SHM) is related to multi‐agent system‐based restoration process (MAS‐based RP) that finds the optimal restoration pattern at the fault condition according to the different zone agents (ZAs) distributing along with the network. This method minimizes the difference between energy cost and flexibility benefit related to the FEM part and difference between the number of switching operation and priority loads restored based on the SHM part. Also, this problem subjects to power flow equations, RESs and active loads constraints, restoration process formulation and system operation limits. Stochastic programming is used to model the uncertainty of loads, energy prices, RESs and EVs. Hereupon, the suggested strategy is implemented on the 33‐bus radial distribution network and it is solved by the crow search algorithm (CSA). Ultimately, the obtained results imply the high flexibility and security of the operation, incorporating the proposed strategy, and delineate the optimal restoration scheme for the ADN.
An insulator inspection method based on deep learning applicable to multi‐scale and occlusion conditions
Authors: Wu Junpeng , Tang Shaobo , Li Xianglei 
Published: March 2021

AbstractAs an important equipment of power system, the insulator's normal operation is the basis to ensure the safe operation of the power system. The insulator positioning and identification technology based on machine vision can quickly and accurately complete the inspection of insulators on site and effectively save the cost of operation and maintenance. This paper proposes an insulator inspection method based on region‐convolutional neural networks (RCNNs). First, the dataset of the insulator image is preprocessed by means of data expansion. Then, the feature extraction of the insulator image is realised by using the zeiler fergus (ZF) network. The k‐means clustering method is used to optimise the selection of anchor points. Meanwhile, the non‐maximum suppression post‐processing algorithm is improved, and a non‐linear penalty factor is introduced to adapt to multi‐scale and overlapping occlusion insulator inspection. Experimental results show that the improved faster RCNNs insulator inspection method can accurately obtain the coordinate frame and the corresponding probability value of the insulator object and improve the average precision by 10.43%, achieving the accurate inspection of the insulator object.
Fragmentation in the massive G31.41+0.31 protocluster
Authors: Beltrán M. T. , Rivilla V. M. , Cesaroni R. , Maud L. T. , Galli D. , Moscadelli L. , Lorenzani A. , Ahmadi A. , Beuther H. , Csengeri T. , Etoka S. , Goddi C. , Klaassen P. D. , Kuiper R. , Kumar M. S. N. , Peters T. , Sánchez-Monge Á. , Schilke P. , van der Tak F. , Vig S. , Zinnecker H. 
Published: March 2021

Context. ALMA observations at 1.4 mm and ~0.′′2 (~750 au) angular resolution of the Main core in the high-mass star-forming region G31.41+0.31 have revealed a puzzling scenario. On the one hand, the continuum emission looks very homogeneous and the core appears to undergo solid-body rotation, suggesting a monolithic core stabilized by the magnetic field; on the other hand, rotation and infall speed up toward the core center, where two massive embedded free-free continuum sources have been detected, pointing to an unstable core having undergone fragmentation.
Aims. To establish whether the Main core is indeed monolithic or if its homogeneous appearance is due to a combination of large dust opacity and low angular resolution, we carried out millimeter observations at higher angular resolution and different wavelengths.
Methods. We carried out ALMA observations at 1.4 mm and 3.5 mm that achieved angular resolutions of ~0.′′1 (~375 au) and ~0.′′075 (~280 au), respectively. VLA observations at 7 mm and 1.3 cm at even higher angular resolution, ~0.′′05 (~190 au) and ~0.′′07 (~260 au), respectively, were also carried out to better study the nature of the free-free continuum sources detected in the core.
Results. The millimeter continuum emission of the Main core has been clearly resolved into at least four sources, A, B, C, and D, within 1″, indicating that the core is not monolithic. The deconvolved radii of the dust emission of the sources, estimated at 3.5 mm, are ~400–500 au; their masses range from ~15 to ~26 M⊙; and their number densities are several 109 cm−3. Sources A and B, located closer to the center of the core and separated by ~750 au, are clearly associated with two free-free continuum sources, likely thermal radio jets, and are brightest in the core. The spectral energy distribution of these two sources and their masses and sizes are similar and suggest a common origin. Source C has not been detected at centimeter wavelengths, while source D has been clearly detected at 1.3 cm. Source D is likely the driving source of an E–W SiO outflow previously detected in the region, which suggests that the free-free emission might be coming from a radio jet.
Conclusions. The observations have confirmed that the Main core in G31 is collapsing, that it has undergone fragmentation, and that its homogeneous appearance previously observed at short wavelengths is a consequence of both high dust opacity and insufficient angular resolution. The low level of fragmentation together with the fact that the core is moderately magnetically supercritical, suggests that G31 could have undergone a phase of magnetically regulated evolution characterized by a reduced fragmentation efficiency, eventually leading to the formation of a small number of relatively massive dense cores.
Bar pattern speeds in CALIFA galaxies
Authors: Cuomo Virginia , Hee Lee Yun , Buttitta Chiara , Aguerri J. Alfonso L. , Maria Corsini Enrico , Morelli Lorenzo 
Published: March 2021

Context. More than 10% of barred galaxies with a direct measurement of the bar pattern speed host an ultrafast bar. These bars extend well beyond the corotation radius and challenge our understanding of the orbital structure of barred galaxies. Most of the bars are found in spiral galaxies, rather than in lenticular galaxies.
Aims. We analyse the properties of the ultrafast bars detected in the Calar Alto Legacy Integral Field Spectroscopy Area Survey to investigate whether they are an artefact resulting from an overestimation of the bar radius and/or an underestimation of the corotation radius or a new class of bars, whose orbital structure has not been understood yet.
Methods. We revised the available measurements of the bar radius based on ellipse fitting and Fourier analysis and of the bar pattern speed from the Tremaine-Weinberg method. In addition, we measured the bar radius from the analysis of the maps tracing the transverse-to-radial force ratio, which we obtained from the deprojected i-band images of the galaxies retrieved from the Sloan Digital Sky Survey.
Results. We found that nearly all the sample galaxies are spirals with an inner ring or pseudo-ring circling the bar and/or with strong spiral arms, which hamper the measurement of the bar radius from the ellipse fitting and Fourier analysis. According to these methods, the bar ends overlap with the ring or the spiral arms, thereby making the adopted bar radius unreliable. On the contrary, the bar radius from the ratio maps are shorter than the corotation radius. This agrees with the theoretical predictions and findings of numerical simulations regarding the extension and stability of the stellar orbits supporting the bars.
Conclusions. We conclude that ultrafast bars are no longer observed when the correct measurement of the bar radius is adopted. Deriving the bar radius in galaxies with rings and strong spiral arms is not straightforward and a solid measurement method based on both photometric and kinematic data is still missing.
Non-thermal escape on Triton driven by atmospheric and ionospheric chemistry
Authors: Gu H. , Cui J. , Niu D.-D. , Wu X.-S. , He F. , Wei Y. 
Published: March 2021

Context. Jeans escape is believed to dominate atmospheric escape for most outer Solar System bodies. However, non-thermal mechanisms, particularly atmospheric and ionospheric chemistry, are likely to contribute substantially to neutral escape on Triton.
Aims. This study is devoted to evaluating the role of the chemically induced escape of H, H2, C, N, O, N2, and CO on Triton via a variety of processes. Here, we also aim to identify the dominant processes for these species.
Methods. We used the background atmospheric and ionospheric structures from available model calculations. We constructed a test particle Monte Carlo model to determine the escape probability profiles of various species released from 35 channels. Species-dependent and energy-dependent cross sections were adopted in our calculations, along with a strongly forward-scattering angle distribution, all constrained by the available laboratory measurements.
Results. The chemical escape rates on Triton are derived as 4.5 × 1024 s−1 for total H, 6.9 × 1022 s−1 for total C, 8.0 × 1024 s−1 for total N, and 1.4 × 1023 s−1 for total O.
Conclusions. Based on a comparison with the respective Jeans escape rates, our calculations indicate that atmospheric and ionospheric chemistry make small but non-negligible contributions to both H and C escape on Triton, whereas its contributions to N and O escape are significant.
On the influence of the air flow resistivity on the measurement of the dynamic stiffness of underlays for floating floors
Authors: Schmelzer Martin , Wittstock Volker , Bietz Heinrich , Brezas Spyros 
Published: March 2021

The dynamic stiffness of underlays is a required quantity to predict the reduction of impact and airborne noise transmitted through floating floors. The measurement of the dynamic stiffness is standardized in ISO 9052–1 using a floating floor section of 200 mm edge length. If open pore insulating materials are used for the underlay, the air flow and its flow resistivity have a significant impact on the dynamic stiffness. The standard ISO 9052–1 therefore calculates the dynamic stiffness based on three distinct intervals of the flow resistivity. This contribution analyses and discusses the mathematical origin and practical consequences of these three standardized intervals and proposes an improvement for a revision of the standard. The current physical model is expanded to examine if the results, that are gained from the geometrically reduced systems of the standard, can be transferred to room sized systems.
Prenatal Diagnosis of Congenital Cataract: Sonographic Features and Perinatal Outcome in 41 Cases
Authors: Qin Yue , Zhong Xiaohong , Wen Huaxuan , Zeng Qing , Liao Yimei , Luo Dandan , Liang Meiling , Tang Yao , Guo Jiaju , Cao Hongrui , Yang Shuihua , Tian Xiaoxian , Luo Guoyang , Li Shengli 
Published: March 2021

Abstract
Purpose To describe the prenatal ultrasonographic characteristics and perinatal outcomes of congenital cataract.
Materials and Methods We analyzed congenital cataract diagnosed prenatally at four referral centers between August 2004 and February 2019. The diagnosis was confirmed by postnatal ophthalmologic evaluation of liveborn infants or autopsy for terminated cases. Maternal demographics, genetic testing results, prenatal ultrasound images, and perinatal outcomes were abstracted.
Results Total of 41 cases of congenital cataract diagnosed prenatally among 788 751 women undergoing anatomic survey. Based on the sonographic characteristics, 16/41 (39.0 %) had a dense echogenic structure, 15/41 (36.6 %) had a hyperechogenic spot and 10/41 (24.4 %) had the “double ring” sign. 17/41 (41.5 %) were isolated, and 24/41 (58.5 %) had associated intraocular and extraocular findings. Microphthalmia, cardiac abnormalities, and central nervous system abnormalities were the most common associated abnormalities. Regarding potential etiology, 6 cases had a known family history of congenital cataract, 4 cases had confirmed congenital rubella infection, and 2 cases had aneuploidy. 31/41 (75.6 %) elected termination and 10/41 (24.4 %) elected to continue their pregnancy. Among the 10 cases, one case died, one case was lost to follow-up, and the remaining 8 cases were referred for ophthalmologist follow-up and postnatal surgery.
Conclusion Once fetal cataracts are detected, a detailed fetal anatomy survey to rule out associated abnormalities and a workup to identify the potential etiology are recommended. Prenatal diagnosis of congenital cataracts provides vital information for counseling and subsequent management.