bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of column reactor results with organic decay by native organic microbiota and varying permeability
Authors: da Silva Maciel Fernanda Costa , Machado Sandro Lemos , de Souza Queiroz Antonio Fernando , Lima Fernando Antonio Leite Vieira
Published: March 2021

Field bio-remediation techniques (FBRT) can be a low cost method to avoid the removal of top layers of soil which are rich in organic matter and bio diversity. The use of native microorganisms in FBRT is preferable because non-indigenous species can transfer their genetic material to the environment with negative impacts on the local ecological equilibrium. Petroleum Produced Water (PPW) is an important pollutant source in onshore production areas. However, due to high sodium concentrations in PPW and the occurrence of organic matter in dissolved and dispersed forms, obtaining pollutant transport parameters may be a difficult task. Results of column tests performed using a natural soil permeated by PPW are presented. All the samples presented a permeability decrease over time and the total hydrocarbon petroleum (TPH) breakthrough curves presented evidence of biological decay. Soil samples underwent biological characterization after tests (Metagenomic analyses and cultural media tests). Curves were modelled in an incremental way using a non-constant decay rate to better simulate the growing process of the microorganisms and consider the occurrence of varying velocity/permeability. Biological characterization results indicate the native organisms that are potentially more able to degrade PPW, including four bacteria (Bacillus and Lysinibacillus genus) and two fungi species (Malassezia and Talaromyces genus) that have not previously been mentioned in the consulted literature. The obtained results contribute to the development of more sustainable FBRTs focusing on native microorganisms, already adapted to the local environmental conditions.
18S rRNA gene sequences of leptocephalus gut contents, particulate organic matter, and biological oceanographic conditions in the western North Pacific
Authors: Watanabe Tsuyoshi , Nagai Satoshi , Kawakami Yoko , Asakura Taiga , Kikuchi Jun , Inaba Nobuharu , Taniuchi Yukiko , Kurogi Hiroaki , Chow Seinen , Tomoda Tsutomu , Ambe Daisuke , Hasegawa Daisuke
Published: March 2021

Eel larvae apparently feed on marine snow, but many aspects of their feeding ecology remain unknown. The eukaryotic 18S rRNA gene sequence compositions in the gut contents of four taxa of anguilliform eel larvae were compared with the sequence compositions of vertically sampled seawater particulate organic matter (POM) in the oligotrophic western North Pacific Ocean. Both gut contents and POM were mainly composed of dinoflagellates as well as other phytoplankton (cryptophytes and diatoms) and zooplankton (ciliophoran and copepod) sequences. Gut contents also contained cryptophyte and ciliophoran genera and a few other taxa. Dinoflagellates (family Gymnodiniaceae) may be an important food source and these phytoplankton were predominant in gut contents and POM as evidenced by DNA analysis and phytoplankton cell counting. The compositions of the gut contents were not specific to the species of eel larvae or the different sampling areas, and they were most similar to POM at the chlorophyll maximum in the upper part of the thermocline (mean depth: 112 m). Our results are consistent with eel larvae feeding on marine snow at a low trophic level, and feeding may frequently occur in the chlorophyll maximum in the western North Pacific.
Validity and reliability of myotonometry for assessing muscle viscoelastic properties in patients with stroke: a systematic review and meta-analysis
Authors: Garcia-Bernal Maria-Isabel , Heredia-Rizo Alberto Marcos , Gonzalez-Garcia Paula , Cortés-Vega María-Dolores , Casuso-Holgado María Jesús
Published: March 2021

There is a lack of consensus about the measurement of the muscle viscoelastic features in stroke patients. Additionally, the psychometric properties of the most-commonly used clinical tools remain controversial. Our objective is to investigate the validity and reliability of myotonometry to assess viscoelastic muscle features in stroke survivors. Pubmed, PEDro, Scopus and Cinahl were systematically searched to include studies reporting the psychometric properties of myotonometric devices used in people after stroke. The QUADAS-2 and the COSMIN checklists were used to assess the methodological quality of the studies and the psychometric properties of myotonometry. Nine studies were included in the qualitative synthesis and data from five of these were pooled in a meta-analysis. Overall, low to moderate risk of bias and applicability concerns were observed. Pooled data from intra-rater reliability for muscle tone showed a mean coefficient of correlation of 0.915 (95% CI: 0.880–0.940, I 2 = 69.2%) for upper limbs, and a mean coefficient of 0.785 (95%CI: 0.708–0.844, I 2 = 4.02%) for lower limbs. Myotonometry seems to be a valid and reliable complementary tool to assess muscle viscoelastic properties in stroke survivors, although definite conclusions about concurrent validity need further research.
Photocatalytic processes for biomass conversion
Authors: de Assis Geovânia C. , Silva Igor M. A. , dos Santos Tiago G. , dos Santos Thatiane V. , Meneghetti Mario R. , Meneghetti Simoni M. P.
Published: March 2021

This review focuses on the photocatalytic conversion of biomass, emphasizing several types of systems, including different photocatalysts and biomass derivatives.
Identification of the key characteristics ofBifidobacterium longumstrains for the alleviation of ulcerative colitis
Authors: Zhang Chengcheng , Zhao Yan , Jiang Jinchi , Yu Leilei , Tian Fengwei , Zhao Jianxin , Zhang Hao , Chen Wei , Zhai Qixiao
Published: March 2021

Identification of the key characteristics of Bifidobacterium longum strains for the alleviation of ulcerative colitis.
Correction: Rhodium-catalysed selective C–C bond activation and borylation of cyclopropanes
Authors: Wang Yandong , Bai Jingyi , Yang Youqing , Zhao Wenxuan , Liang Yong , Wang Di , Zhao Yue , Shi Zhuangzhi
Published: March 2021

Correction for ‘Rhodium-catalysed selective C–C bond activation and borylation of cyclopropanes’ by Yandong Wang et al., Chem. Sci., 2021, DOI: 10.1039/d0sc06186g.
Studies on situation reasoning approach of autonomous underwater vehicle under uncertain environment
Authors: Yin Lili , Chen Deyun , Gu Hengwen , Guan Ning , Zhang Rubo , Hou Handan
Published: March 2021

The purpose of this study is to provide a situation reasoning module for autonomous underwater vehicle (AUV), to make decision‐making agents know what is the current situation, what needs to be done in the present situation, and what is the risk of task present situation. This will enhance efficiency for AUV. Situation reasoning for AUV aims to communicate mission assessments to decision‐making agents. Thus, in solving this problem, it is important to design a new situation reasoning module for AUV. This article is presenting the situation reasoning module for AUV, which includes uncertain event detection, uncertain event recognition and ontology model of the situation. The article concludes by demonstrating the benefits of the situation reasoning module in a real‐world scenario. A situation reasoning simulation is demonstrated in an AUV while performing a complex mission. The approach was validated by marine experiments and simulating experiments for AUV. Results show the effectiveness of situation reasoning approach.
Seamless transition of microgrid between islanded and grid‐connected mode of operation
Authors: Chandak Sheetal , Rout Pravat Kumar
Published: March 2021

Microgrids 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

To 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

The 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

The 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

Single 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

This 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

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

Coronary 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.
Epitaxial deposition of LaF3 thin films on Si using deep eutectic solvent based facile and green chemical route
Authors: Rahman Md. Hafijur , Ahmmed Shamim , Tabassum Samia , Ismail Abu Bakar Md.
Published: March 2021

Epitaxial lanthanum fluoride (LaF3) is considered an important and outstanding material for the fabrication of Metal–Insulator–Semiconductor (MIS) capacitive devices. In the quest of finding a green and low-cost scalable technique for the epitaxial deposition of LaF3 thin-film, this article presents an investigation on a home-made deep eutectic solvent (DES)-based chemical route for LaF3 thin film deposition on p-type silicon (p-Si) using the spin coating technique. The x-ray diffraction study confirmed the epitaxial deposition of LaF3 film on the p-Si substrate. An almost pinhole-free homogeneous surface and nearly stoichiometric epitaxial LaF3 were observed on the Si substrate through scanning electron microscopy and energy dispersive x-ray spectroscopy, respectively. From the capacitance–voltage (C–V) characteristics, the capacitance of the Ag/LaF3/p-Si/Ag device with four-layer LaF3 was maximum among the Ag/LaF3/p-Si/Ag devices with two-layer, four-layer, and six-layer LaF3. The flat band potential of the Ag/LaF3/p-Si/Ag structure was determined from the Mott–Schottky plot. The experimental results indicate that the DES-based epitaxial deposition of LaF3 film on the p-Si substrate could be a highly promising technique for the fabrication of LaF3-based MIS capacitive devices.
Comparison of water nanodroplet properties on different graphite-based substrates
Authors: Goswami Monojoy , Kumar Navin , Li Yuzhan , Rios Orlando , Akamo Damilola O. , Hirschey Jason , LaClair Tim J. , Gluesenkamp Kyle R.
Published: March 2021

The molecular structure and dynamics of water differ considerably at various interfaces. We compare the interfacial water structure–property relationship on three different carbon substrates, namely, amorphous carbon, compressed expanded natural graphite, and pure graphite by utilizing atomistic molecular dynamics simulations. The effect of different substrates on the structural and dynamical properties of water can readily be observed. The density distributions parallel and normal to the substrates show oblate droplet structures. The normal to the substrate water distribution shows a strong hydration layer at the interface that does not vary with substrates. However, the disparity in the structure and dynamics on three different substrates shows that the surface morphologies of the substrates are critical for determining nanoscale water properties. Furthermore, it is observed that the formation of an interfacial water layer or the hydration layer is a direct consequence of both water “confinement” at the nanoscale and “attraction” between water molecules and the carbon substrates.
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

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

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

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

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

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

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

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.
A test method for manufacturing effect assessment in HCF
Authors: Beghini M , Bertini L , Macoretta G , Monelli B D , Arcioni M , Bagattini A , Grilli M , Tognarelli L
Published: March 2021

Surface conditions produced by manufacturing processes are known to significantly affect the fatigue strength of metallic materials. However, fatigue tests on planar specimens usually present the onset of fatigue crack in a specimen edge, where the superposition of different machining techniques and subsequent machining operations can hide the effects of the studied process. This study deals with the design of a fatigue test able to reliably assess the effects on the high cycle fatigue strength of any machining process used to produce planar surfaces. It was devised a test configuration where the specimen geometry and the loading conditions are aimed to locate the crack nucleation in the middle of the surface machined by the investigated process. This condition is achieved by employing a notched specimen and a three-point bending test configuration, where the position and geometry of the notches are designed to relieve the specimen’s edges. Nevertheless, in the critical region, the stress state is quite uniaxial and uniform in the longitudinal direction. The specimen is manufactured by using the same parameters and processes adopted for full-scale components, thus producing a surface with the same properties as the real component. The designed test configuration was validated in a high cycle fatigue test aimed to compare the effects of broaching and wire electrical discharge machining on the Wöhler curve (S-N curve). The specimen geometry was tailored for a broaching process so that it has sufficient stiffness both in the directions parallel and perpendicular to the broaching direction. Fatigue tests were carried out on a resonant machine, that allowed to detect the crack nucleation by monitoring the test frequency.
Thermographic-DIC approach in fatigue behaviour analysis
Authors: Barbagallo R , Fargione G , Giudice F , La Rosa G
Published: March 2021

A research program was carried out by a group of researchers of nine Italian universities in order to define the fatigue parameters of a commercial steel. The purpose is to define the fatigue limits in different loading conditions and comparing the results obtained by tests performed using different energetic methodologies. In this paper the thermographic method already proposed in literature was performed, determining the Haigh and Goodman-Smith limit curves. At the same time, the thermal response in static tests were derived in order to correlate the limit of the totally thermoelastic behaviour.
Acoustic Emission Techniques for Evaluating Damage Modes in CFRP Hybrid Joints
Authors: Barile C , Casavola C , Pappalettera G , Vimalathithan PK
Published: March 2021

The Acoustic Emission (AE) technique is one of the powerful Non-Destructive Evaluation (NDE) tools for predicting and assessing damages in composite structures. In this research work, the energy released during each acoustic event, as a function of the total number of counts, is used for evaluating the damage modes in CFRP hybrid joints. The damage modes identified using the AE parameter, Energy per Count (

E

A
E

n

) is compared with the waveforms of the acoustic events. Generally, the type of damage mode can be identified by postprocessing the acoustic waveforms. By comparing the waveforms with the

E

A
E

n

, the damage mode has been evaluated. The technique introduced in this work will reduce the data storage and computation time for analyzing the waveforms. The damage modes can be identified during loading using this technique. In addition to that, the location of the generated acoustic events is used for identifying the critical failure areas in the CFRP hybrid joints. The attenuation of the AE events due to the distance between the sensors and the AE source is also considered for this study. From the observed results, the AE technique proves to be one of the formidable techniques for evaluating damage modes in composite structures.
Biomechanical evaluation of titanium trabecular sphere in kyphoplasty procedure
Authors: Krüger A , Francaviglia N , Di Bella S , Mineo R
Published: March 2021

The treatment of osteoporotic vertebral compression fractures using transpedicular augmentation has grown significantly during the past two decades. Balloon Kyphoplasty allowed to restore vertebral height and to improve the deformity, but has several disadvantages related to the filler material used: the bio-cement. The aim of the current study is to investigate the mechanical behaviour of cadaveric fractured osteoporotic vertebral treated with a new filler material made by Spheres in Trabecular Titanium alloy (Ti6Al4V-ELI), under static loading conditions. The Strength of the VBs remain almost the same. So, the VBs maintain their physiological values after the kyphoplastic procedure with trabecular titanium sphere. The stiffness was instead significantly reduced in some VBs. This data can be affected to the limit of ex vivo study.
Influence of infill percentage on the mode I fracture toughness of adhesively bonded Double Cantilever Beam joints with Additively Manufactured PLA adherends
Authors: Moroni F , Pirondi A , Bergonzi L , Vettori M
Published: March 2021

Adhesive bonding can disclose the possibility to additively manufacture (AM) smaller, highly optimized objects to be bonded in post-production into/onto larger components. However, the infill shape and percentage can influence the fracture toughness of a bonded joint as it emerges from the literature Since the choice of the infill yields also a significant impact on manufacturing time, it is important to assess clearly its influence on bonded joint strength in order to balance strength and manufacturing issues. Therefore, in this work the Mode I fracture toughness of PLA bonded joints obtained by FFF will be assessed as a function of infill percentage, from solid (100% infill) to 20% infill. Test will be done using a Double Cantilever Beam (DCB) joint bonded with a PolyUrethane (PU), room temperature-curing adhesive.
On the use of shape memory alloys for deployable passive heat radiators in space satellites
Authors: Bacciotti A , Bucchi F , Frendo F , Mameli M , Perna R , Filippeschi S
Published: March 2021

The present work presents a multifunctional structure for space engineering application part of the TOPDESS project, funded by ESA.

The main aim of the project is the design of a thermal control device able to deploy through passive actuation. A combined device has been designed, made up of a Pulsating Heat Pipe (PHP) foldable heat exchanger and Shape Memory Alloy (SMA) wire. The deployment of the SMA wire is conceived to be controlled by thermal contact with the heat source and by conduction along the wire. Since the heat sources are lumped and the wire is subject to convection, a temperature gradient develops along the wire.

A monodimensional mode able to predict the behavior of an SMA wire subjected to a spatial temperature gradient, is presented in this paper.

The results show that the system can carry out folding and unfolding cycles with rotation angles greater than 80° only if the wire is subjected to uniform temperature distribution; in the case of temperature gradient, the achievable rotation angle is about 20°.

The analysis states the feasibility of the actuation system, highlighting the critical technological aspects, to lay the groundwork for the future development of the whole system.
Laser Powder Bed Fusion: A Review on the Design Constraints
Authors: Ceccanti F , Giorgetti A , Arcidiacono G , Citti P
Published: March 2021

With the creation of additive manufacturing production lines and the adoption of additive technologies, such as Laser Powder Bed Fusion, as standard manufacturing technologies for the mass production of parts, many considerations arise. In particular, product quality assurance is surely a very important aspect to be considered when talking about mass production. Laser powder bed fused parts are characterized by specific characteristics, such as quite rough surfaces and internal cavities filled with powder after the part construction. The need to ensure part quality and the importance to guarantee quality to all the parts made within the production line highlights the need to design the part addressing all the criticalities resulting from the manufacturing process, in addition to the ones related to the operative conditions. In this work, the attention is placed on two important topics: part surface inspectability and part cleaning. In particular, part inspectability is a crucial aspect in determining part coherence with design specifications. Part production via LPBF puts interpretability issues in inspecting the parts. Part cleaning is a crucial topic as well. Part cleaning is related to the design of the part to guarantee a correct powder evacuation from all the internal channels and cavities. Within the work, problems will be defined and design guidelines will be proposed to manage these topics.
Experimental validation of miniaturized specimen developed to perform uniaxial tensile test on high performance materials
Authors: Bergonzi L , Vettori M , Moroni F , Musiari F , Pirondi A
Published: March 2021

This work deals with the experimental validation of the proposed specimens geometries which design process through Finite Element Method was presented during AIAS 2019 and published afterwards [1]. In particular, non-conventional miniaturized specimen geometry compliant to ASTM E8 and ISO 6892, specifically developed to work with MaCh3D [2], an innovative miniaturized tensile testing machine, were considered. The size-reduction of specimens is advantageous both in terms of material and equipment: smaller specimens require lower forces to be broken, hence a compact tensile testing machine can perform the mechanical characterization activity. In this experimental validation, mechanical properties determined using the three proposed MaCh3D miniaturized specimens are compared to full-size ISO 6892 samples. Specimens were cut from AISI 304 stainless steel plates, with different thickness according to specimens requirements. Good accordance has been found between the standard and non-standard geometries.
Analysis of belt transmissions capabilities using the brush model
Authors: Bucchi F , Frendo F
Published: March 2021

The mechanics of power transmission is usually modeled by two different theories: the creep theory and the shear theory. Recently, the authors introduced an alternative theory based on the brush model, which allows to compute the tangential stress distribution along the winding arc of pulleys. The brush model is able to predict the speed loss along the driving and driven pulley as a function of the transmission parameters (e.g. pre-load, friction, pulley radii etc.) and the operating parameters (i.e. angular speed and resistant torque). In addition, the energy efficiency of the system is obtained by knowing the speed loss and the energy dissipation; this contribution can be subdivided into energy loss due to friction and energy loss due to the non-recoverable elastic deformation of the bristle.

In the present paper, using the previously developed model, a sensitivity analysis aimed at mapping the transmission capabilities as a function of geometry and operating parameters is proposed. These results, given as look-up table (or contour plot), are very important in mechanical systems simulation (e.g. real-time systems, hardware in the loop systems) since they allow to introduce the phenomenological behavior of the pulley-belt transmission without introducing complex models in the simulation.
Experimental modal analysis of SSR1 cryomodule for numerical model tuning and validation
Authors: Barnaba A , Bucchi F , Neri P , Passarelli D
Published: March 2021

The present activity aims to test the Cryomodule SSR1 to validate the corresponding mixed multibody-finite element numerical model and to determine the range of frequencies in which the first natural modes of the structure lie. The experimental activity consisted of a hammer test of the cryomodule at an early assembly stage at which the internal parts, constituting the cold mass, are accessible and, thus, many accelerometers can be attached to the beam string. The comparison between the experimental results obtained for the sub-assembly and the numerical results obtained for the corresponding sub-model, derived from the previously developed complete model, allowed to assess the validity of the numerical model and to get feedback on the effectiveness of the placement of the sensors in capturing the dynamic response of the system during transportation.
Influence of design parameters on the penetration resistance of machine guards
Authors: Landi L , Vittori M , Stecconi A , Valigi M C
Published: March 2021

In the last years, different research on ballistic penetration of machine tools guards, as defined in EU Directive 2006/42/EC, were conducted in different worldwide laboratories. Even if the design of machine safety guards using the material/thickness are defined in annexes of ISO standardization, a revision of those annexes is expected in next years. Standardized tests have some limitations because they are performed using a given penetrator that impacts perpendicularly the surface of flat plates of about 500 mm x 500 mm. In this paper the influence of some design parameters will be investigated by polycarbonate sheets of 4mm thickness. The evaluation of ballistic limit for 4 mm sheets of 300 mm x 300 mm and 500 mm x 500 mm size will be presented. Moreover, the influence of constraint on ballistic limit of standardized 500 mm x 500 mm sheets will be also presented by two different constraint devices: one similar to a border hinge constraint, one to a border rigid clamping. Discussion of results will be presented with a view to review the ISO standardization annexes on ballistic penetration.