bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seamless transition of microgrid between islanded and grid‐connected mode of operation
Authors: Chandak Sheetal , Rout Pravat Kumar 
Published: March 2021

AbstractMicrogrids and their smart interconnection with utility are the major trends of development in the present power system scenario. Inheriting the capability to operate in grid‐connected and islanded mode, the microgrid demands a well‐structured protectional strategy as well as a controlled switching between the modes. This challenging task is dealt with in this study, by the proposed centralized smart mode transition controller (CSMTC). The controller embarks upon two major microgrid protection aspects, by incorporating the protectional strategy against unintentional islanding and auto‐reclosing. Subsequent to the protection of the microgrid, the smooth operation of the microgrid has also been a major focus of the proposed study. Therefore, the switching of microgrids between the modes (i.e. grid‐connected to islanded or vice‐versa) has been engaged in the proposed controller. Energy storage‐based distributed static synchronous compensator (E‐STATCOM) is integrated at the point of common coupling to support the performance of the controller. E‐STATCOM performs to compensate the switching transients, along with maintaining the steady‐state system stability. The CSMTC integrated with E‐STATCOM protects the microgrid against unwanted system faults and supports a seamless transition between the modes by controlling the interconnecting static switch. To verify the operation of the proposed control strategy, the microgrid test model is simulated on the podium of MATLAB 2015b/Simulink.
Significant enhancement in the electrical conductance properties of ethylene propylene diene monomer using the nano‐SiO2 particles
Authors: Xu Chunyu , Zhao Ruixue , Li Chuanyang , Li Yuanyuan , Zhang Guodong , Shahsavarian Tohid , Yuan Mengqiang , Lei Zhipeng 
Published: March 2021

AbstractTo study the effect of nano‐silica particles on the conductivity characteristics of ethylene propylene diene monomer (EPDM) insulation, EPDM nanocomposites with different mass fractions of nano silica were prepared via the melt‐blending method. Scanning electron microscopy was used to analyze the dispersion of nanoparticles in EPDM. Based on the Fourier‐transform infrared spectrum, the bonding properties between the nanoparticles and EPDM were analyzed. The steady‐state current at 30–100 °C and 1–20 kV/mm was measured. Moreover, the conductivity characteristic was analyzed. The experimental results show that as the content of nano‐silica increases, the electrical conductivity of EPDM nanocomposite as well as the threshold field strength gradually decreases. Samples with a small number of nanoparticles will increase the activation energy of the carrier conductivity, and the interface region effect introduced by nanoparticles will reduce the carrier mobility and concentration, resulting in a lower conductivity. Comparing the calculated value of the dielectric constant with the measured value can conclude that the high‐field conductance process is a combination of the electrode effect and the body effect, which in this case, Schottky effect dominates.
Numerical modelling of MOV with Voronoi network and finite element method
Authors: Zhou Qibin , Yang Hongxiang , Huang Xin , Wang Manyu , Ren Xin 
Published: March 2021

AbstractThe electrical and thermal characteristics of metal oxide varistor (MOV) are essential for the study of MOV performance and degradation. This paper provides a modelling method of MOV to simulate its microstructure geometry with the Voronoi network and derive the electrical functions on the grain boundaries. A series of discrete data to describe the resistance‐voltage (R–V) characteristics of MOV from experiments is applied to the proposed model. Through 8/20 μs surge current experiments, the electrical conductivity of MOV is determined to achieve the simulation of the clamping voltage. With this model, the current distribution and temperature distribution over a MOV sample are simulated and analysed by the finite element method (FEM). The simulation results show good agreement with the experimental measurement and inherent feature of MOV.
Calculation of conductive ions distribution in icicle and melting water conductivity
Authors: Liu Yanqing , Shu Lichun , Hu Qin , Jiang Xingliang , Zhu Meilin , Yu Jianbo 
Published: March 2021

AbstractThe flashover problem of ice‐covered insulators has seriously affected the safe operation of transmission lines. Numerous researches have shown that the high conductivity water film on the surface is determined by the conductive ions distribution in the icicle which is the key factor affecting the flashover voltage of ice‐covered insulators. In our previous work, the conductive ions distribution in the icicle has been obtained through experiments and simulation analysis. In order to calculate the conductivity of the water film, the conductive ion‐specific content at different positions in the icicle has been calculated mathematically. In addition, based on the simulation of icicle melting process, the icicle melting process is analysed, and the melting water conductivity of the icicle is calculated. Moreover, melting ice test is carried out in artificial climate chamber to verify the validity of the calculation method. The calculated results are in good agreement with the test results. The conclusion obtained here would provide theoretical basis for establishing a flashover model of ice‐covered insulators.
A pyramid non‐local enhanced residual dense network for single image de‐raining
Authors: Zhao Minghua , Fan Hengrui , DU Shuangli , Wang Li , Li Peng , Hu Jing 
Published: March 2021

AbstractSingle image de‐raining based on convolutional neural network (CNN) has made considerable progress in recent years. However, usually the de‐rained result has dark artifacts and image textures tend to be over‐smoothed. In this paper, a pyramid non‐local enhanced residual dense network is proposed to reduce such distortion. Firstly, the down‐sampled images are input into the Laplacian pyramid, which can extract the overall and partial texture clues, and subsequently a set of images of different scales are produced. Secondly, these images are fed into a non‐local enhanced residual dense block, which can not only capture long‐distance dependencies of feature maps, but also fully utilizes the hierarchical features in every dense block, leading to high accuracy of rain streaks extraction and better preservation of image edge detail. Finally, the de‐rained image is gradually restored by Gaussian reconstruction pyramid. Experimental results on both synthetic data and real‐world data show that the artifacts distortion is obviously reduced by the proposed network. And the quality of de‐rained image is significantly improved compared with the state‐of‐the‐art methods.
A new compact and wideband quadrature feeding network with an integrated asymmetrical phase shifter
Authors: Lyu Yun‐Peng , Li Bo , Zhu Lei , Cheng Chong‐Hu 
Published: March 2021

AbstractThis article reports a new class of quadrature feeding network which integrates an asymmetrical phase shifter to obtain the compact size and wideband property simultaneously. By adjusting the impedance of two loading stubs, this asymmetrical phase shifter can realize 90° phase shift, impedance transformation, and phase slope alignment at the same time. Operation principle and design procedure for this introduced quadrature feeding network are provided with synthesis equations and design curves. By using the shape of Archimedes gradual‐change lines, the area of this circuit layout is fully utilized, and the overall size of the proposed feeding network is only 0.050λg2. Compared with a traditional compact design, this technique can effectively enhance the amplitude balance bandwidth by 1.7 times (from 58% to 101%) and phase balance bandwidth by 5.9 times (from 14% to 83%) as well as keep the circuit size nearly unchanged under the same conditions. To verify the design concept, two prototypes of the quadrature feeding networks are designed, fabricated, and tested. Good agreement between the measured and simulated results is achieved and they well reveal the attractive wideband equal amplitudes and 90° phase balance performance for this proposed new compact quadrature feeding network.
Atlantoaxial Stabilization by Posterior C1 and C2 Screw-Rod Fixation for Various Pathologies: Case Series and Comprehensive Review of Literature
Authors: Unni Chandramohan , Pettakkandy Vijayan , P. Abdul Jaleel , Soren Subrat Kumar , K. Vineeth K. 
Published: March 2021

Abstract
We retrospectively analyzed atlantoaxial dislocation (AAD) of various pathologies, namely, rheumatoid arthritis (RA), os odontoideum, and trauma. Various techniques were discussed in relation to C1-C2 stabilization. The study aims to share our clinical experience in a series of six cases of C1-C2 instability that underwent posterior C1-C2 fusion, with free hand technique and limited fluoroscopy. The clinicoradiological presentation for each patient is described. We reviewed different literatures related to our case vividly and focused on the basic neuroanatomy involved in the atlantoaxial joint. All patients of AAD had evidence of severe canal compromise and chronic compressive spinal cord changes. In our study, the patients age ranged from 28 to 52 years. The study included four males and two females. Out of six patients of AAD, three had history of trauma, two had os odontoideum, and one had chronic inflammatory condition (RA). From our case series, we concluded that the Goel–Harms technique is the most versatile and surgeon friendly technique for C1-C2 fixation. Early recognition and surgical intervention of atlantoaxial joint instability is essential to prevent catastrophic neurological complications.
Pathophysiology, Diagnosis, and Management of Coronary No-Reflow Phenomenon
Authors: Kaur Gagan , Baghdasaryan Patrick , Natarajan Balaji , Sethi Prabhdeep , Mukherjee Ashis , Varadarajan Padmini , Pai Ramdas G. 
Published: March 2021

AbstractCoronary no-reflow phenomenon is a lethal mechanism of ongoing myocardial injury, following successful revascularization of an infarct-related coronary artery. Incidence of this phenomenon is high following percutaneous intervention, and is associated with adverse in-hospital and long-term outcomes. Several mechanisms such as ischemia-reperfusion injury and distal microthromboembolism in genetically susceptible patients and those with preexisting endothelial dysfunction have been implicated. However, the exact mechanism in humans is still poorly understood. Several investigative and treatment strategies within and outside the cardiac catheterization laboratory have been proposed, but have not uniformly shown success in reducing mortality or in preventing adverse left ventricular remodeling resulting from this condition. The aim of this article is to provide a brief and concise review of the current understanding of the pathophysiology, clinical predictors, and investigations and management of coronary no-reflow phenomenon.
Envelope analysis applied to non-Hertzian contact simulations in damaged roller bearings
Authors: Brusa E , Bruzzone F , Delprete C , Di Maggio L , Rosso C 
Published: March 2021

Abstract
In the latest years many researcher focused on the possibility to foresee the failure of a mechanical system in the early stages in order to allow quick response times. Monitoring and diagnostics are at the base of those methodologies of predictive maintenance, which represents the standard for companies. Data acquired by monitoring systems are sometimes not sufficient to perform an effective diagnosis and to detect failures. In the present work the possibility of a defining a relation between the response of a system and the dimension of a defect causing the vibration is explored. Through a non-Hertzian contact model a roller bearing is studied and a correlation is sought between the size of the defect and the frequency content of the contact pressure time history. Resorting to a non-Hertzian approach enables the determination with good accuracy of the overpressures due to edge effects caused by the sudden change in curvature in presence of a defect. The estimation of the pressure variation can be used to estimate the amplitude of the harmonic content exciting the bearing during operation. Using algorithms for the signal analysis already assessed in the literature, in particular the envelope method, an in-depth analysis of the harmonic content of the signal to consider is possible. The possibility of building a correlation between the load and the size of the defect which might help to identify the dimension of a damage from the estimated frequency content. It is then possible to identify the presence and nature of the defect, allowing an early diagnosis of the failure.
Evaluation of the effect of profile modifications in gears subjected to sudden torque inversion
Authors: Bruzzone F , Maggi T , Marcellini C , Rosso C , Delprete C 
Published: March 2021

Abstract
The search for propulsion systems of vehicles with lower environmental impact is focusing on systems with exclusive or supplementary use of electric motors. In fully electric or hybrid vehicles, the electric power delivery is used not only to provide torque to the vehicle and the consequent movement of the vehicle, but also to transform the vehicle’s kinetic energy back into electrical energy for storage in batteries when the vehicle is downhill or it must be slowed down. Under normal operating conditions, even in urban usage, it is common to have sudden inversions of the power flow. This means that in a really short time the motor switches from delivering torque to receiving it. Normally the electric motor is not directly connected on the wheels, but a geared transmission is present. The change of torque from positive (motor) to negative (generator) causes a sudden change of the working conditions. This induces vibrational and durability problems on the gears. In the present paper, an accurate model of mesh dynamics is proposed, capable of considering the inversion of the power flow. This model evaluates the forces exchanged between the teeth both with the variation of the torque and the rotation speed. Through the evaluation of the variation in gear stiffness it allows to evaluate the transmission response to different operating conditions. The possibility of establishing which side is in contact and which is the direction of the force exchanged between the mating teeth allows to evaluate the effect on the dynamic response of the system. In this way it is possible to decide which is the best shape of the teeth which minimises the dynamic response of the system in all operating conditions, including torque inversion.
Mechanical response of an high-strength automotive steel at different strain rates and evolution of damage-related parameters
Authors: Mirone G , Barbagallo R , Tedesco M M , De Caro D , Ferrea M 
Published: March 2021

Abstract
The present work concerns a thin sheet high-strength steel of interest for automotive applications. The extended constitutive curves in static and dynamic conditions were determined by tensile tests on smooth specimens. Further tests carried out on notched specimens were simulated both to validate the elastoplastic response and to analyse the evolution of the relevant parameters related to ductile damage (triaxiality and Lode angle) in the critical areas of the specimens (diffuse and localized necking), studying the correlations between the trend of these quantities and the mode/location of the fracture initiation. The analysis of the images of the specimens acquired during the tests allowed to characterize in detail the behaviour of the material up to breakage, also providing different experimental references to validate the numerical simulations of the tests on the smooth and notched specimens.
Analysis of the intervention of an anti-fall device in Motorcycle Autonomous Emergency Braking (MAEB) experimental tests
Authors: Biffoli Andrea , Lucci Cosimo , Marra Mirko , Savino Giovanni 
Published: March 2021

Abstract
Motorcycle Autonomous Emergency Braking (MAEB) is a rider assistance that may soon play a role for the improved safety for Powered-Two-Wheeler users. Several studies were carried out to investigate the feasibility of automatic braking (AB) events. In a recent experiment, tests were conducted with volunteer participants to assess AB intervention under different riding conditions. The prototype vehicles were equipped with an anti-fall device (outriggers), the main object of this study, to ensure participants’ safety. The outriggers limit the roll angle of the motorcycle, thus preventing accidental capsize. Data from the sensors installed on the side arms were analyzed to identify ground contact events, for which a correlation with the driving style adopted by the participants has emerged. There was one case in which MAEB activation was followed by outriggers intervention. However, detailed analysis indicated that this could not be assimilated to an incipient fall. Our results show that the simple sensor setup was able to gather useful information for the experimental tests.
A new statistical software for the estimation of P-S-N curves in presence of defects: statistical models and experimental validation
Authors: Tridello A. , Paolino D.S. 
Published: March 2021

Abstract
It is well-known in the literature that fatigue failures originate from the weakest element within the component loaded volume. In particular, for metallic materials the fatigue crack typically nucleates from the most critical surface defect in the High-Cycle-Fatigue (HCF) region; whereas, it generally nucleates from the most critical internal defect in the Very-High-Cycle-Fatigue (VHCF) region, at stress amplitudes below the so-called ‘transition stress amplitude’. Therefore, regardless of the fatigue region, the P-S-N curves must necessarily take into account the random distribution of the critical defect size. However, in the literature, there are few statistical models that can model the dependency between the fatigue life and the defect size or that can take into account the presence of different failure mechanisms (e.g., surface crack nucleation in HCF and internal crack nucleation in VHCF). In the present paper, a new software for the estimation of the P-S-N curves is proposed. The statistical P-S-N models recently proposed by the authors and implemented in the software are described in the paper. The procedure for the parameter estimation is also explained in detail and the software is finally validated with experimental datasets collected by the authors or available in the literature.
High temperature biaxial compressive strength of a commercial isotropic ultrafine grain graphite
Authors: Centofante L , Monetti A , Meneghetti G 
Published: March 2021

Abstract
Graphite is widely used in industrial applications, thanks to its excellent high temperature resistance. Therefore, its mechanical strength under combined stress at high temperature is an important issue for structural design. This work reports biaxial compressive data of an isotropic ultrafine grain graphite, the POCO EDM-3. Uniaxial tests have been first performed at room temperature with plane specimens, in order to obtain the stress strain curve for this material. Compressive tests have been then carried out with different notched geometries, both at room temperature and at 1000°C, in order to evaluate the biaxial compressive strength. Since plastic deformation was observed in uniaxial compressive tests with plane samples, elastic-plastic simulations have been performed with the FE code Ansys®, in order to assess the stress state at failure. The applicability of the Von Mises yield criterion has been evaluated, by comparing the equivalent Von Mises stresses at failure in different notched geometries. The tests demonstrated that, at room temperature, this type of graphite plastically deform in compression and that the Von Mises criterion can be used in order to evaluate the stress state. Moreover, the comparison between the failure loads at room temperature and at 1000°C showed that the resistance increases as the temperature increases.
Isolating trabecular morphology to study bone damage
Authors: Buccino F 
Published: March 2021

Abstract
Bone structure is particularly complex and characterized by an intricate hierarchical architecture. Consequently, bone damage occurs at the multi-scale. Clinical applications typically analyze bone fractures at the macro-scale, but currently damage modes at lower scales are not fully understood yet. This research focuses on the understanding of meso-scale damage, characterized by a network of trabeculae of different thickness and spatial orientation. In order to isolate this articulated morphology, bone samples from porcine vertebrae are scanned through micro-computed tomography (micro-CT) and replicated by means of selective laser melting technique (SLM), obtaining Ti6Al4V specimens. This is particularly useful, because these samples are realized with a uniform material, permitting to isolate morphological features. The SLM samples, after a check of the internal morphology, are mechanically tested under static compression. The load-displacement curve shows a first linear elastic section, followed by a collapse of the structure. This behavior is similar to the one of porcine vertebrae. Starting from micro-CT volume reconstruction, three finite element models are implemented. A global preliminary model of the entire sample is developed and the area with the highest level of strain is identified. In order to understand the distribution of stresses and strains in the critical zone, a sub-region of the original cylinder is considered. The results of the simulations identify a homogeneous distribution of deformations over the entire geometry, with the exception of the region characterized by a thinning of the trabeculae, called the failure band of the sample. By implementing an additional sub-model, the most strained trabecula is identified as the critical location, causing the collapse of the structure. The numerical models are then validated by comparing the numerical and experimental stiffness. This will allow to perform further analyses by varying the trabecular architecture and quantitatively evaluate the effect of morphology.