bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of TiO2 grain size on performance of Ba0.5Sr0.5TiO3 based capacitors for energy storage application
Authors: P. S. Smitha , S. Jayan Jitha , Appukuttan Saritha , V. Suresh Babu , G. Shiny
Published: January 2021

Performance of energy storage devices, particularly metal‐insulator‐metal capacitors are evaluated mainly by leakage current and specific capacitance. The insulator material BaSrTiO shows high specific capacitance owing to its high relative permittivity. In this work, BaSrTiO nanopowder is synthesized using commercially available TiO nanopowder (ACS reagent grade) as well as using synthesized TiO nanopowder from Ti isopropoxide. The crystallinity and grain sizes of commercially available and synthesized TiO nanopowder differ. The effects of crystallinity and grain size of TiO nanopowder on specific capacitance and leakage current density of BaSrTiO ceramic based metal‐insulator‐metal capacitors are investigated in this paper. An 88 % reduction in grain size is achieved in TiO nanopowder synthesized from Ti isopropoxide compared to commercially available TiO nanopowder. A 45 % enhancement in specific capacitance and 57 % enhancement in leakage current are achieved in BaSrTiO ceramic based metal‐insulator‐metal capacitor synthesized using TiO nanopowder with lower grain size. The lower leakage current of metal‐insulator‐metal capacitor with BaSrTiO ceramic of low grain size is investigated with its structure using X‐ray powder diffraction pattern analysis as well. The BaSrTiO ceramics synthesized using TiO nanopowder with lower grain size is a suitable candidate for insulator material in metal‐insulator‐metal capacitors for energy storage application.
Study of the magnetic properties of Mn‐doped iron titanate nanoparticles fabricated using natural mineral
Authors: Senthil Sutha , Nattanmai Raman Dhineshbabu , Sundaramoorthy Arunmetha
Published: January 2021

In this study, iron titanate (FT) and manganese‐doped iron titanate (MFT) nanoparticles were synthesised from a natural mineral, ilmenite ore, using a simple and effective method. X‐ray diffraction analysis confirmed the reduction of crystallite size from 56 to 29 nm with an increase in Mn doping concentration from 0% to 2%. Doping of Mn transformed the agglomerated fine particles into nanosphere‐like morphology with dimensions less than 200 nm. Magnetization studies revealed that FT and MFT were hard ferrimagnetic materials, and beyond 0.8% Mn dopant concentration, reduction in magnetic saturation value of 1.46–1.41 emu g−1 was observed. Resistivity of FT decreased from ≈19 to ≈2 K Ω‐cm with doping Mn and tuning of such electrical property through doping concentration can lead to their application in fabricating spintronic devices. This work suggests a new pathway to synthesise magnetic–semiconducting nanostructures at large scale and in an environment friendly manner from ilmenite ore.
Magnetic, optical, structural and thermal properties of copper ferrite nanostructured synthesized by mechanical alloying
Authors: Younes Abderrahmane , Kherrouba Nabil , Bouamer Amirouche
Published: January 2021

CuFe2O4 spinel nanostructured were elaborated by mechanical alloying technique from Cu, Cu2O and Fe2O3 under controlled atmosphere with different milling times at room temperature. The CuFe2O4 spinel crystalline has a body‐centred tetragonal structure at low temperatures with lattice parameters a ≅ 0.582 nm and c ≅ 0.869 nm and face‐centred cubic structure at high temperatures with lattice parameter a ≅ 0.842 nm. The average crystallite size and lattice strain determined from X‐ray diffraction for CuFe2O4 are 22.12 ± 5.47 nm and 0.781 ± 0.082 %, respectively. The FTIR‐ATR spectra of the samples shows that the vibration around of 400–1000 cm−1 corresponds to the CuFe2O4 absorbed at octahedral and tetrahedral sites. The mechanical alloying process results in CuFe2O4 agglomerated in clusters, which radically change their shape during milling time. Differential scanning calorimetry analysis shows two additional endothermic peaks around 715–781 °C and 863–957 °C, the first peak might be affected to the formation of Cu‐Fe‐O and the second peak may correspond to the transformation of CuFe2O4 from tetragonal to cubic structure. CuFe2O4 samples milled until 20 h are ferromagnetic at room temperature with saturation magnetization increasing from 29.8 to 59.6 emu/g with increasing the milling time. The coercivity decreases 254 Oe up to 230 Oe when the milling time increases from 0 to 20h.
Effect of carbon quantum dots on the photo‐absorption, photo‐response and photoelectrochemical performance of KNb3O8 film photoelectrode
Authors: Liu Xiaobin , Tan Tianjian , Que Wenxiu , Zhou Huanfu , Wang Kangguo
Published: January 2021

The KNb3O8 crystals and carbon quantum dots were synthesized via hydrothermal reaction method, their crystal structural and morphological properties were investigated by X‐ray diffraction, scanning electron microscope and transmission electron microscope, respectively. The X‐ray diffraction patterns of KNb3O8 film on FTO glass (SnO2 conductive glass doped with fluorine) show that the thin KNb3O8 crystals are apt to stack along the [020] direction of KNb3O8 crystal structure. Scanning electron microscope and transmission electron microscope results indicate that most of KNb3O8 crystals have a width of about 0.5 μm and a length of more than 5 μm and the carbon quantum dot has a graphite structure with a size of about 3 nm. The UV‐response KNb3O8 thin film electrode was loaded by carbon quantum dots and showed broader photo‐absorption characteristic (up to visible light region) and higher photocurrent (a bias of 0.4 V vs SCE), as compared of the pristine KNb3O8 film electrode. In addition, their photo‐electrochemical (PEC) performances were also investigated under different light irradiation conditions with an applied potential between −0.4 and 0.7 V versus SCE.
Experimental studies on viscosity, thermal and tribological properties of vegetable oil (kapok oil) with boric acid as an additive
Authors: Shankar Subramaniam , Manikandan M. , Raja G. , Priyadharashini G. Suganya , Pramanik Alokesh
Published: January 2021

Non‐renewability and damage caused to the environment while using mineral based and synthetic based lubricants become the greatest concern of this century. Disposal issues initiated a global trend to utilize vegetable based lubricants in industries. Vegetable oils are environmental friendly, have low toxicity and highly biodegradable in nature. The main objective of this work is to improve the viscosity and reduce the friction and wear rate of Kapok oil using boric acid as an additive. The tribological properties of kapok oil with three different concentrations (1, 3 and 5 wt%) of boric acid is evaluated and compared with pure kapok oil using pin on disc tribometer. The worn out surface of the pin are analyzed using the optical microscope after the wear test. The viscosity and thermal properties of kapok oil with 5 wt% of boric acid possess the better performance compared to other samples. Boric acid particles suspension exhibits reduction in friction and wear when compared with pure kapok oil. Overall, the kapok oil combined with 5 wt% of boric acid acts as the better bio lubricant oil which would help to reduce the global demand of petroleum‐based lubricant sustainability.
Crystallization investigation of BaTiO3 coating layer on Ni nanoparticles
Authors: Qin Jing , Hao Yanan , Guo Limin , Bi Ke
Published: January 2021

The crystallization of oxide coating layer on base metal electrode (BME) has facing challenges for a long time. In this paper, a sol‐gel method was used to coat nickel (Ni) nanoparticles with polycrystalline BaTiO3 (BT). By adjusting the reaction condition, continuous and homogeneous BT coating layer was obtained based on the transmission electron microscopy (TEM) observation. Powder X‐ray diffraction (XRD) of the coated sample indicated that deionized water content, which can change the pH value of the reaction solvent, is the key factor to influence the crystallization of the BT layer. With the increase of the deionized water, the crystallinity of the BT layer increased, which greatly enhanced the anti‐oxidation properties of the Ni nanoparticles. When the amount of deionized water increased to 20 wt%, Ni3C impurity appeared and the properties of the Ni nanoparticles deteriorated. As a result, an optimized deionized water content of 16 wt% is adopted for the best performance of the BT coated Ni (Ni@BT) nanoparticles.
Estimation of the capacitor voltages in flying capacitor multi‐level converters
Authors: Escalante Miguel F. , Erdmann Alex P.
Published: January 2021

Flying capacitor multi‐level converters use charged capacitors as a critical element. For proper operation, the capacitor voltages must be known and regulated. Direct measurement is straightforward, but when the number of required measurements is high, this is a complicated approach. This paper introduces an estimation method for n capacitor voltages. The scheme is based on a system of () equations, which is defined in a way that it incorporates information of the actual capacitor voltages and open‐loop estimates of the capacitor voltages. The solution of the system gives the best estimates of the capacitor voltages in the sense of least square errors. The method requires only output voltage and output current sensors and its computational burden is low, saving cost and design efforts, and simplifying the hardware system. The performance of the proposed scheme is evaluated experimentally in a 9‐level flying capacitor chopper, where the estimates are used by the voltage balancing strategy and by the output current controller.
Optimal energy scheduling of a solar‐based hybrid ship considering cold‐ironing facilities
Authors: Vahabzad Neda , Mohammadi‐Ivatloo Behnam , Anvari‐Moghaddam Amjad
Published: January 2021

There are many restrictions on shipping, which reduce or prohibit the use of diesel generators for feeding the energy demand of the electric ships, especially in ports. Therefore, the use of shore power system (SPS) together with renewable energies and energy storage systems (ESSs) can lead to many environmental benefits while ships are berthing in ports. In this study, the shipboard hybrid power system (HPS) is proposed, including diesel generators, solar photovoltaic panels (PV), ESS and cold‐ironing (CI) facilities for using SPS to efficiently supply the ship's electrical demand. With such HPS aboard, the solar generated power is estimated accurately based on the navigation route. By optimal energy scheduling in a real hybrid cruise ship, the use of diesel generators gets minimised, due to the utilisation of PV and ESS. In addition, using CI service instead of switching on auxiliary diesel generators in ports leads to a 3 h increase in charging and discharging times of the ESS. Furthermore, the efficient use of CI service results in less use of diesel generators even at sailing hours, reducing emissions and minimising the costs of supplying ship's energy demand. The total cost reduction of the HPS in different case studies, without the use of CI services is only 1% to 2%, while this reduction is about 6% to 7% by adding the CI facilities to the HPS. Moreover, the economic characteristics of the proposed diesel‐PV‐ESS‐CI by adding the CI facilities to the HPS are analysed and the profitability of this HPS in reducing the daily costs with considering the share of installation costs on the target day is proved.
Two stage unit commitment considering multiple correlations of wind power forecast errors
Authors: Wang Chengfu , Li Xijuan , Zhang Yumin , Dong Yunhui , Dong Xiaoming , Wang Mingqiang
Published: January 2021

When the correlation of wind power output among wind farms is not considered, the integrated stochastic characteristics of wind power will not be captured accurately. Using this inaccurate feature may lead to an impractical even a failing result of unit commitment (UC). Therefore, this paper proposes a multiple correlations model for wind power forecast errors (WPFEs), and to capture this multiple correlation feature in UC problem, a two‐stage chance‐constrained interval UC (CIUC) model is proposed. First, an analytical expression of multiple correlations, including spatial, temporal and conditional correlations, is presented to improve the description accuracy of stochastic WPFEs. To strike a balance between risk and operational cost, a chance‐constrained decision method is developed to optimize the time‐varying interval of wind power output in the first stage. Subsequently, an interval UC model is established to determine the optimal operational schedule in the second stage. Finally, the proposed CIUC model is solved using a solution strategy that combines column‐and‐constraint generation and sample average approximation. The effectiveness and practicality of the proposed method are verified via the numerical results for IEEE 39‐bus and 118‐bus systems.
Impact of converter‐interfaced renewable generations on breaker failure protection of the emanant transmission lines
Authors: Radhakrishnan Asha , Das Sarasij
Published: January 2021

The presence of Converter Interfaced Generations (CIGs)
poses significant challenges to traditional protection schemes. This paper
studies the impact of CIGs on the Breaker Failure Protection (BFP) of
transmission lines emanating from CIGs. The instantaneous over‐current (50BF) setting and reset time of BFP have been
investigated. Fault current contribution of CIGs is usually comparable with
load currents. Low fault current contribution by CIGs may lead to significant
loss of security of BFP because of the existing practice of using lower setting
for 50BF. This paper proposes a voltage‐dependent adaptive setting of 50BF
element to enhance the security of BFP schemes while maintaining dependability.
Use of voltage helps in differentiating loads from fault situations. In traditional power systems, CT
subsidence current is known to delay the reset of BFP schemes. The impact of
low fault contribution by CIGs on the reset time of BFP has been studied.
Mathematical expression for CT subsidence current, which influences the reset
time, has been derived. It is observed that the BFP reset may not be delayed if
the fault current seen by the breaker is low due to the presence of CIG.
Discussions on the dependability and
security of proposed 50BF setting are also presented.
One‐sample optimal output smoothing method for wind farm with energy storage system
Authors: Koiwa Kenta , Ishii Tomoya , Liu Kang‐Zhi , Zanma Tadanao , Tamura Junji
Published: January 2021

This paper proposes a novel optimization method for energy storage systems (ESSs) to smooth wind farm output to satisfy the technical requirements and reduce the rated power (rated energy capacity) and charge/discharge loss of the ESS. The state of charge of the ESS operated by the proposed method can be regulated, guaranteeing some constraints. The proposed method has a very simple structure, does not require the wind farm output forecast and numerical optimization, such as particle swarm optimization. Therefore, a high‐grade functional computation device is not needed. The effectiveness of the proposed method is verified by comparative analysis with conventional approaches through simulations.
Efficient energy management system using Internet of things with FORDF technique for distribution system
Authors: Vinjamuri Usha Rani , Rao B. Loveswara
Published: January 2021

Energy management system for the distribution system using Internet of things with hybrid technique. The proposed hybrid technique is the joined execution of both the fruitfly optimisation algorithm and random decision forest and named as FORDF strategy. The main objective of the proposed system is to optimally manage the power and resources of distribution system by persistently screen the data from the Internet of things‐based communication system. In the proposed system, each home device is interfaced with data acquisition module with IP address bringing about a huge work wireless network of devices. So as to encourage the improvement of demand response for distribution system to deal with the energy, the Internet of things‐based communication system is utilised. So as to ideally deal with the energy, the optimal load demand prediction and the energy control PROCESSES are handled by the FORDF system. Besides, the optimum utilisation of the accessible resources and the flexibility of such networks are given and expanded by the Internet of things based distribution system. Furthermore the proposed technique is qualified to satisfy the general SUPPLY and energy demand. At long last, the proposed model is implemented in MATLAB/simulink platform and the exhibition is contrasted and different systems
Risk‐constrained optimal bidding strategy for a wind power producer with battery energy storage system using extended mathematical programming
Authors: Abhinav Rishabh , Pindoriya Naran M.
Published: January 2021

Wind power producers (WPP) in India, currently, are restricted from participating in the short‐term energy market due to the uncertainty in their power generation. Consequently, they might lose an excellent opportunity to maximise their revenue. WPPs, with installed BESS and proper risk management, could promisingly participate in the market and minimise the penalty for deviating from the schedule. This paper devises an optimal bidding strategy for a WPP to participate in the day‐ahead and real‐time energy markets considering the uncertainties present in wind power generation and market electricity price. At the same time, it also aims to minimise the power deviation during real‐time delivery. The paper incorporates CVaR as a risk measure and formulates a two‐layer stochastic optimisation problem while employing multiple scenarios of the uncertain data. The upper layer of the problem decides the day‐ahead offering, while the lower layer deals with the real‐time operation. The stochastic problem is further reformulated using extended mathematical programming, which benefits in reducing the mathematical complexity of the problem. Wind power data from an actual wind farm located in Gujarat, India is taken as a test‐study. Various potential case‐studies are presented to illustrate the effectiveness of the proposed bidding strategy.
Research on random fuzzy power flow calculation of AC/DC hybrid distribution network based on unified iterative method
Authors: Yang Guokang , Dong Ping , Liu Mingbo , Wu Huayi
Published: January 2021

In recent years, with the promotion of policies and technologies, a large number of distributed generations are connected to the urban distribution network in various forms. At the same time, the flexible DC transmission technology has become mature and gradually applied to the distribution network. In this condition, the AC/DC hybrid distribution networks with flexible regulation ability will be the trend of urban distribution network. This paper accurately considers the loss of voltage source converter, and proposes a unified iterative power flow method for AC/DC hybrid distribution network, which takes the voltage source converter control modes into account. Because of the uncertainties of the distributed generations and loads, a random fuzzy power flow model is proposed, in which cumulant method is applied in the random stage. In the fuzzy stage, the fuzzy simulation technology is applied. Finally, an improved PG&E 69‐Bus system is taken as an example to verify the effectiveness of the unified iterative method and the random fuzzy power flow calculation, and put forward some suggestions for the operation of distribution network with distributed generations.
A five bus AC–DC hybrid nanogrid system for PV based modern buildings
Authors: Dutta Subhendu , Chatterjee Kishore
Published: January 2021

A five bus AC–DC hybrid transformerless nanogrid system for modern buildings, and its associated control strategy that can operate all the buses simultaneously, is proposed in this paper. The nanogrid has five buses that can exchange power among themselves. This feature improves the reliability of power availability in the system. Two DC buses and one AC bus can be operated in standalone mode as well as in grid connected mode which enables the scheme to operate with available DC microgrids and the AC utility grid. The PV array and the battery bank are interfaced with the remaining two buses which are PV bus, and the battery bus, respectively. In order to reduce the number of serially connected battery units, the voltage rating of the battery bus is kept low. Similarly, the voltage rating of the PV bus is maintained at a medium level to decrease the number of serially connected modules. Hence the effect of shading is minimized. The control strategy of the system is developed to judiciously operate all the buses. In order to validate the viability of the system, exhaustive experimental studies are carried out utilising a laboratory scale 1.2 kW nanogrid system developed for the purpose.
An Analytical method for detecting instability in grid‐connected doubly‐fed induction generator
Authors: Nasab Mohammad Rajabi , Yaghobi Hamid
Published: January 2021

Doubly‐fed induction generator (DFIG) is among the most attractive technologies in wind farms. As the penetration of wind power into the grid has increased in recent years, protecting of wind farm's generators against grid disturbances has become a major issue for the power system industry. Transient instability (TI) is among the most frequent phenomena due to severe grid disturbances. This phenomenon might cause significant damages to network equipment. In DFIG based wind turbine (WT), when the crowbar circuit is activated, the rotor winding is short‐circuited and the power converter is blocked. At this moment, the DFIG operational mode is temporarily changed to squirrel‐cage induction generator (SCIG). This lead to reactive power absorption and voltage drop, that might cause electromechanical oscillations and unstable condition. This study presents an analytical method for detection TI of a grid‐connected DFIG based on analysis of angular velocity and acceleration data, which are readily obtained from locally measured quantities. This technique works on a setting‐free manner, i.e. revising would not be required even when the network configuration changes, which is a favourable feature in protective relaying. The performance of the proposed method is verified using MATLAB/Simulink. Simulation results prove the method's reliability and simplicity.
An MMTES algorithm for dynamic photovoltaic array reconfiguration to enhance power output under partial shading conditions
Authors: Varma G Harish Kumar , Barry Venugopal Reddy , Jain Rohit Kumar , Kumar Devanand
Published: January 2021

Partial shading is a severe impediment to the effective use of photovoltaic systems. It will lead to performance degradation in the photovoltaic system. This work proposes a maximum–minimum tier equalisation swapping reconfiguration algorithm for total‐cross‐tied connection under shading conditions. The proposed reconfiguration algorithm uses a switch matrix to alter the interconnection of modules in a photovoltaic array. The switch matrix dynamically modifies the connections based on the equalisation of tier irradiance. This algorithm applies to the symmetrical and asymmetrical photovoltaic array. Further, simulation studies show the efficacy of the proposed algorithm by minimising the multiple peaks and enhancing the output power compared with the traditional total‐cross‐tied configuration. The performance of experimental tests ascertains the feasibility of the proposed method.
Performance evaluation and modelling of the Atir marine current turbine
Authors: Díaz‐Dorado Eloy , Carrillo Camilo , Cidras Jose , Román David , Grande Javier
Published: January 2021

In this study, the behaviour of a full‐size prototype of a platform for tidal energy was analysed. The turbine of this platform is formed by two counter‐rotating rotors aligned with the tidal current, such that one rotor is always under the wake of the upstream rotor. The platform was tested under real working conditions; the tidal current was emulated by towing. The results of these tests were used to develop and parameterize a turbine model, which is presented in this paper. The turbine was modelled in terms of power, torque, and thrust coefficients. This model was used to estimate the power curve of the platform and design control strategies that, in addition to maximizing energy production, contribute to the stability of the platform.
Global maximum power point tracking in partially shaded PV systems using plant reproduction algorithm
Authors: Krishnan G. Satheesh , V. Puthusserry Gireesh , T. Mithun , P. Simon Sishaj , P. Thazhakuni Bijilesh
Published: January 2021

The power–voltage curve of photovoltaic (PV) power generation system under partial shading conditions (PSC) is non‐monotonic with multiple power peaks and traditional methods do not guarantee global convergence which leads to energy loss. This paper proposes a new tracking scheme for global maximum power point (GMPP) on a shaded PV system based on plant reproduction algorithm (PRA). The concept of PRA is suitably tailored towards maximum power point tracking (MPPT) and lucidly explained in this work. The algorithm is applied towards MPPT in several shaded PV architectures through computer simulations and later verified through experimentation. Computed and measured results show that PRA quickly identifies GMPP and further provides significantly improved MPPT characteristic curves compared to established alternatives.
Robust load frequency control for networked power system with renewable energy via fractional‐order global sliding mode control
Authors: Lv Xinxin , Sun Yonghui , Hu Wenqiang , Dinavahi Venkata
Published: January 2021

Owing to random load changes and transmission time delays in interconnected power systems with renewable energy, the load frequency control scheme has become one of the main methods to keep stability and security of power systems. To relieve communication burden and increase network utilisation, an adaptive event‐triggered scheme is explored. Then, a new fractional‐order global sliding mode control scheme comprising the fractional‐order term in the sliding surface is adopted to improve robustness of load frequency control. The fractional‐order term generates a new degree of freedom and more adjustable parameters to improve control performance. Furthermore, the Markov theory is applied in the modelling process to better describe the uncertainty of parameters and external disturbances. The stability and stabilisation criteria for multi‐area power systems load frequency control are put forward by employing the improved Lyapunov function and integral inequalities with auxiliary functions. Finally, two simulation examples containing a two‐area power system and modified IEEE 39‐bus New England test power system with three wind farms are presented to investigate the effectiveness of the proposed method.
Operational strategy optimisation of VRB energy storage systems considering the dynamic characteristics of VRB in active distribution networks
Authors: Lei Jiazhi , Gao David Wenzhong , Liu Jinhong
Published: January 2021

Strategy optimisation of large‐scale battery energy storage system (BESS) operation in active distribution networks (ADNs) is an actively pursued research topic concerned by electric power researchers. This study proposes a dynamic programming method (DPM)‐based operational strategy optimisation of vanadium redox flow battery (VRB) ESSs for the comprehensive performance of ADNs considering the dynamic characteristics of VRB. The dynamic characteristics of VRB based on self‐discharge rate, dynamic efficiencies, maximum absorption power, cycle life and apparent power are reasonably proposed to construct the operational restrictions of ESSs. VRB is safely and reasonably operated with high cycle life and ideal states by these dynamic operational restrictions. And then, DPM is used to decompose the multivariate optimisation problem into several univariate optimisation problems. Finally, different case studies showed that the developed operation strategy of VRB ESSs can greatly improve both the economy and the voltage quality of ADNs. Also, the curtailment rate of renewable energy in ADNs is greatly reduced by about 50% and VRB ESSs can get a perfect optimisation associated with a higher utilisation rate of about 0.8 and an ameliorative average efficiency of about 0.753.
Transient modelling of doubly‐fed induction generator based wind turbine on full operation condition and rapid starting period based on low voltage ride‐through testing
Authors: Yan Xiangwu , Cui Sen , Sun Xuewei , Sun Ying
Published: January 2021

Transient simulation model of doubly‐fed induction generator‐based wind turbine has a complex model structure and considerable control parameters. An accurate simulation model is especially important for studying the static and transient characteristics of doubly‐fed induction generator‐based wind turbine and the grid‐connected system. Based on the measured data of low voltage ride‐through testing, the integrated parameter identification method is proposed here. Combined with the time‐domain simulation analysis, curve fitting is used to determine the control strategy of doubly‐fed induction generator‐based wind turbine. The improved genetic algorithm is used to identify the generator parameters, power control parameters, and resistance of Crowbar of doubly‐fed induction generator‐based wind turbine. Combined with the electrical parameters provided by the wind turbine manufacturer, electromagnetic transient model on full operation condition and rapid starting period, corresponding to a measured doubly‐fed induction generator‐based wind turbine in West Inner Mongolia Power Grid, is then established, which can operate in the full wind speed range and quickly enter the stable state within 1 s after start‐up. Comparison of simulation results and measured data shows that the established electromagnetic transient simulation model using parameters identified by the proposed method can accurately reflect the key characteristics of doubly‐fed induction generator‐based wind turbine.
Planning for resilience in power distribution networks: A multi‐objective decision support
Authors: Jamborsalamati Pouya , Garmabdari Rasoul , Hossain Jahangir , Lu Junwei , Dehghanian Payman
Published: January 2021

Power grid response against high‐impact low‐probability (HILP) events could be enhanced by (a) hardening mechanisms to boost its structural resilience and (b) corrective recovery and mitigation analytics to improve its operational resilience. Planning for structural resilience and attempts to find the optimal location of the Tie switches in radially operated power distribution networks that enable harnessing the network topology for maximised resilience against HILP disasters are focussed. This goal is achieved through a novel resilience‐oriented multi‐objective decision making platform, which employs a k‐PEM based probabilistic power flow (PPF) algorithm. The proposed framework offers a decision making analytic embedded with the fuzzy satisfying method (FSM) that characterises the system resilience features, such as robustness, restoration agility, load criticality, and recovered capacity, to assess different network reconfiguration options and select the optimal solution for implementation. The aforementioned resilience features are formulated in nodal level and then aggregated over the entire system to characterise the system‐level objective functions. The performance of the suggested framework is analysed on the IEEE 33‐Bus test system under a designated HILP event, and the applicability on larger networks has been verified on the IEEE 69‐bus test system. The results demonstrate the efficacy and applicability of the proposed framework in boosting the network resilience against future extremes.
Index modulation for OFDM RadCom systems
Authors: Huang Gaojian , Ding Yuan , Ouyang Shan , Fusco Vincent
Published: January 2021

This paper studies a novel Radar and wireless communication fusion system namely, RadCom, using orthogonal frequency division multiplexing index modulation waveforms. From the communication perspective, information is conveyed not only through modulated orthogonal frequency division multiplexing subcarriers but also by the active subcarrier indices that are dynamically updated at the transmitted symbol rates. When compared with conventional orthogonal frequency division multiplexing communication systems, only a subset of subcarriers is activated in the proposed orthogonal frequency division multiplexing index modulation system, which reduces signal peak‐to‐average ratios, leading to enhanced power amplifier efficiency. From the Radar sensing perspective, the Radar range‐velocity profile obtained using compressed sensing approach is simulated and presented. It is shown that orthogonal frequency division multiplexing index modulation RadCom system can enhance the transmission data rates when low‐order modulation schemes are adopted e.g. binary phase shift keying, and maintain similar Radar performance compared with the orthogonal frequency division multiplexing counterpart when the system is carefully designed.
Optical wireless power transmission characteristics of surface appearance controlled solar cells using visible colour filters
Authors: Liu Yu , Miyamoto Tomoyuki
Published: January 2021

Optical wireless power transmission (OWPT) systems are attractive photonic systems based on light sources and solar cells. To improve the visual design of practical consumer applications, we applied visible colour filters to change the normal black appearance of solar cells. Different colours made by multilayer‐type filters on solar cells were investigated for control of visible colour with maintained power transmission efficiency. The surface colours seen by the eyes and standard cameras were controlled by the filter as expected from the filter spectral response. The electrical output characteristics of the solar cell covered with the filter were experimentally measured in order to confirm the OWPT performance. The results showed that the OWPT system can change colour appearance with an acceptable slight deterioration of performance.
The impact of inlet flash evaporation conditions on erosion damage characteristics of coal gasification black water angle valve and prevention strategies
Authors: Yan Xu , Wei Wang , You Ming , Fan-Ding Li , Hao-Zhe Jin
Published: January 2021

In view of the three-stage flash evaporation system of the coal gasification plant, a combination of theoretical analysis and numerical simulation was used to establish the erosion damage evaluation model in the black water angle valve. The influence of the inlet flash evaporation ratio on the inlet velocity, the outlet flash evaporation ratio and the outlet velocity of the low-pressure black water angle valve are systematically studied, the mechanism of erosion damage to the carbon steel valve body by the solid medium in black water was analyzed according to the micro-cutting theory. The results show that the inlet velocity w
1, the outlet flash evaporation ratio x
2, the outlet velocity w
2 of angle valve have linear correlation with the inlet flash evaporation ratio x
1.The upstream volume erosion ratio of the angle valve at the inlet flash ratio x
1 = 3 wt.% is 114 times as much as that at zero inlet flash ratio. Meanwhile, the downstream volume erosion ratio of the angle valve at x
1 = 3 wt.% is only 2.7 times as much as that at zero inlet flash ratio. The prevention strategies to reduce the erosion damage to black water angle valve are proposed by inhibiting the inlet flash evaporation ratio and reducing the inlet flow rate etc. This study is expected to provide guidance for the erosion resistance design and operation of the black water angle valve.
Predictive Value of Transcranial Evoked Potential Monitoring for Intramedullary Spinal Cord Tumors
Authors: Ille Sebastian , Wagner Arthur , Joerger Ann Kathrin , Wostrack Maria , Meyer Bernhard , Shiban Ehab
Published: January 2021

Background Intraoperative neurophysiologic monitoring (IONM) has increased patient safety and extent of resection in patients with eloquent brain tumors. Despite its comprehensive capability for the resection of intramedullary spinal cord tumors (ISCTs), the application during the resection of these tumors is controversial.

Methods We retrospectively analyzed the resection of ISCTs in 83 consecutive cases. IONM was performed in all cases. Each patient's motor status and the McCormick scale was determined preoperatively, directly after surgery, at the day of discharge, and at long-term follow-up.

Results IONM was feasible in 71 cases (85.5%). Gross total resection was performed in 75 cases (90.4%). Postoperatively, patients showed new transient deficits in 12 cases (14.5%) and new permanent deficits in 12 cases (14.5%). The mean McCormick variance between baseline and long-term follow-up was − 0.08 ± 0.54. IONM's sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for the patient's motor status at the day of discharge was 75.0%, 64.7%, 45.5%, and 86.8%. It was 88.9%, 59.7%, 24.2%, and 97.4% for the motor outcome at long-term follow-up. Patients experienced postoperative complications in 15 cases (18.1%).

Conclusion IONM, as performed in the present study, shows a high sensitivity and NPV but low specificity and PPV, particularly for the patient's motor status at the long-term follow-up. As far as practicable by a retrospective study on IONM, our results confirm IONM's usefulness for its application during the resection of ISCTs. However, these results must be approved by a prospective study.
Sensitivity and Negative Predictive Value of Motor Evoked Potentials of the Facial Nerve
Authors: Bovo Nicolas , Momjian Shahan , Gondar Renato , Bijlenga Philippe , Schaller Karl , Boëx Colette
Published: January 2021

Objective The objective of this study was to determine the performance of the standard alarm criterion of motor evoked potentials (MEPs) of the facial nerve in surgeries performed for resections of vestibular schwannomas or of other lesions of the cerebellopontine angle.

Methods This retrospective study included 33 patients (16 with vestibular schwannomas and 17 with other lesions) who underwent the resection surgery with transcranial MEPs of the facial nerve. A reproducible 50% decrease in MEP amplitude, resistant to a 10% increase in stimulation intensity, was applied as the alarm criterion during surgery. Facial muscular function was clinically evaluated with the House–Brackmann score (HBS), pre- and postsurgery at 3 months.

Results In the patient group with vestibular schwannoma, postoperatively, the highest sensitivity and negative predictive values were found for a 30% decrease in MEP amplitude, that is, a criterion stricter than the 50% decrease in MEP amplitude criterion, prone to trigger more warnings, used intraoperatively. With this new criterion, the sensitivity would be 88.9% and the negative predictive value would be 85.7%. In the patient group with other lesions of the cerebellopontine angle, the highest sensitivity and negative predictive values were found equally for 50, 60, or 70% decrease in MEP amplitude. With these criteria, the sensitivities and the negative predictive values would be 100.0%.

Conclusion Different alarm criteria were found for surgeries for vestibular schwannomas and for other lesions of the cerebellopontine angle. The study consolidates the stricter alarm criterion, that is, a criterion prone to trigger early warnings, as found previously by others for vestibular schwannoma surgeries (30% decrease in MEP amplitude).
Long-Term Success of Metal Endobronchial Stents in Lung Transplant Recipients
Authors: Izhakian Shimon , Wasser Walter , Unterman Avraham , Fruchter Oren , Gorelik Oleg , Kramer Mordechai
Published: January 2021

Background Bronchial stenosis is a common complication following lung transplantation. We evaluated long-term associations of the use of self-expandable metal stents (SEMSs) with lung function tests, patient safety, and survival.

Methods A retrospective chart review of 582 lung transplantations performed at our institution between January 2002 and January 2018. Fifty-four patients with SEMSs (intervention group) were matched one-to-one to patients without SEMSs (control group) using propensity score matching for age, sex, the year, and type of transplantation (unilateral/bilateral), and underlying disease. Data regarding long-term lung function and survival were compared between the groups.

Results During a median follow-up of 54.8 months, the difference in survival between the study groups was not statistically significant (p = 0.2). Following 5, 7.5 and 10 years, values of mean forced expiratory volume in 1 second (FEV1) were comparable between patients with and without SEMSs as follows: 59.5 versus 62.6% (p = 0.2), 55.9 versus 55.0% (p = 0.4), and 63.5 versus 61.9% (p = 0.3), respectively. In the intervention group, a significant increase in the mean FEV1 was observed in 60 days after stent insertion (from 41.9 ± 12.8 to 49.5 ± 16.7% days, p < 0.001). Long-term complications following stent insertion included severe bleeding (1.8%), stent fractures (7.4%), stent stenosis (7.4%), stent collapse (3.7%), endobronchial pressure ulcer (1.9%), and stent migration (1.9%).

Conclusion SEMS insertion is associated with a positive sustained effect on lung function, without increasing long-term mortality. Thus, airway stenosis after lung transplantation can be safely and successfully treated using endobronchial metal stenting, with tight bronchoscopic follow-up and maintenance.
Economic Impact of Diagnostic Imaging in the Workup of Uncomplicated Bell's Palsy
Authors: Kazemian Elycia , Schaffer Hollie Marie , Wozniak Amy , Leonetti John P.
Published: January 2021

Objective Our primary objective is to identify the costs associated with imaging in the diagnostic workup of uncomplicated Bell's palsy. Our secondary objective is to identify a dollar amount spent on extraneous diagnostic testing on a state and national level.

Design and Setting Retrospective chart analysis was performed at our tertiary care medical center between 2007 and 2018. International Statistical Classification of Diseases-10 code G51.0 was used to identify patients with Bell's palsy seen by the senior author. A total of 163 patients were divided into two groups: those having received imaging and those diagnosed without imaging. The imaging group was then further subdivided by imaging modality: computed tomography (CT) only, magnetic resonance imaging (MRI) only, or both. There was a total of 138 scans in 115 patients. To quantify the amount spent by insurance companies or patients on these scans, net expected pay (NEP) for each modality was used as a representation of cost. The NEP for a CT was $618. The NEP for an MRI was $1,119. The NEP for both scans was $1,737. We extrapolated our results to a state and national level.

Main Outcome Measurements Cost of workup; state and national economic burden.

Results Extrapolating our data, we forecast that in Illinois and in the United States, over $2 million and $53 million, respectively, are spent on unnecessary imaging.

Conclusion By highlighting an unnecessary financial burden, our study provides concrete evidence to support the American Academy of Otolaryngology's recommendation that clinicians should not perform routine imaging studies when diagnosing uncomplicated Bell's palsy.
Mother-to-Child HIV Transmission among Pregnant Women in a City with the Highest Rates of HIV in Brazil
Authors: Menegotto Mariana , Magdaleno Amanda M. , da Silva Carmem L.O. , Friedrich Luciana , da Silva Clécio H.
Published: January 2021

Objective Most of the HIV pediatric infections are acquired through mother-to-child transmission (MTCT). Porto Alegre is a state capital of Brazil that had a HIV MTCT rate of 4.1% in 2013 and the highest rate of HIV-infected pregnant women in the country during 2018. Zidovudine and nevirapine have been used in Brazil for high-risk newborns since 2012. The aim of the study was to investigate HIV MTCT rate and the factors associated with HIV transmission at a hospital that is a reference center for HIV-infected mothers in Porto Alegre, after the introduction of this policy.

Study Design This retrospective cohort study included all HIV-exposed infants born between February 2013 and December 2016 at the Hospital de Clínicas de Porto Alegre. Student's t-test or Fisher's exact test was used to compare variables between HIV-infected and uninfected groups of newborns. Poisson's regression with robust variance was used to determine the factors associated with HIV MTCT.

Results A total of 375 newborns were exposed to HIV, with an outpatient loss of 14.4% (n = 54). The HIV MTCT rate was 2.18% (n = 7), with four infected during the intrauterine period. The risk factors for MTCT were no prenatal care (relative risk [RR] = 9.4; 95% confidence interval [CI]: 2.0–44.3), late maternal HIV diagnosis in the peripartum period (RR = 16.3; 95% CI: 3.6–73.0), syphilis infection during pregnancy (RR = 9.3; 95% CI: 2.1–40.3), maternal viral load >1,000 copies/mL in the third trimester or peripartum period (RR = 9.5; 95% CI: 1.7–50.5), and lack of or inappropriate antiretroviral therapy during pregnancy (RR = 8.2; 95% CI: 1.6–41.4).

Conclusion MTCT rate was 2.18%. With the institution of two-drug prophylaxis for high-risk newborns, persistent cases HIV MTCT were predominantly found among women with absence of antenatal care, late HIV diagnosis, syphilis coinfection, high viral load, and inadequate ARV therapy during pregnancy. Although zidovudine and nevirapine were administered postnatally to high-risk newborns, this regimen could not prevent transplacental transmission.

Key Points
Auditory Brain Stem Response Predictors of Hearing Outcomes after Middle Fossa Resection of Vestibular Schwannomas
Authors: Ren Yin , Merna Catherine M. , Tawfik Kareem O. , Schwartz Marc S. , Friedman Rick A.
Published: January 2021

Objectives To analyze the relationship between preoperative and intraoperative auditory brain stem response (ABR) characteristics and hearing outcomes in patients with vestibular schwannomas (VS) undergoing hearing preservation (HP) surgery via a middle cranial fossa (MCF) approach.

Design Prospective study.

Setting Academic tertiary skull base referral center.

Methods Pre- and postoperative pure-tone average (PTA) and word recognition score (WRS) were examined. Intraoperative ABR wave III latency, wave V latency, and amplitude were recorded. HP was defined as postoperative WRS ≥50%.

Participants Adult patients with VS and WRS ≥50% who underwent MCF tumor resection between November 2017 and September 2019.

Main Outcome Measures Postoperative hearing outcomes.

Results Sixty patients were included. Mean tumor size was 9.2 mm (range, 3–17). HP rates were 56.7% for the cohort and 69.7% for tumors <10 mm. A complete loss of wave V was associated with an 82.9% increase in postoperative PTA (p < 0.001) and 97.2% decrease in WRS (p < 0.001), whereas a diminished wave V was correlated with 62.7% increase in PTA (p < 0.001) and 55.7% decrease in WRS (p = 0.006). A diminished or absent wave V, but not increased wave III/V latency or decreased wave V amplitude, was correlated with a decline in postoperative hearing class (r = 0.735, p < 0.001). Receiver-operating characteristic analysis demonstrated that a stable wave V has the highest accuracy in predicting HP (sensitivity of 82.6%, specificity of 84.8%).

Conclusion Of the examined preoperative and intraoperative ABR characteristics, a stable wave V intraoperatively was the strongest predictor of HP after MCF resection of VS.

Level of Evidence Level III.