bluuebunny/crossref_metadata_2025 huggingface dataset:
Strength Characteristics of Electrospun Coconut Fibre Reinforced Polylactic Acid: Experimental and Representative Volume Element (RVE) Prediction
Authors: Ogunbiyi Olugbenga , Gbenebor Oluwashina , Salifu Smith , Olaleye Samuel , Jamiru Tamba , Sadiku Rotimi , Adeosun Samson
Published: September 2022

Environmental conservation and waste control have informed and encouraged the use of biodegradable polymeric materials over synthetic non-biodegradable materials. It has been recognized that nano-sized biodegradable materials possess relatively good properties as compared to conventional micron-sized materials. However, the strength characteristics of these materials are inferior to fossil-based non-biodegradable materials. In this study, biodegradable polylactide (PLA), reinforced with treated coconut husk particulates (CCP) for improved mechanical properties, was fabricated using an electrospinning process and representative volume element (RVE) technique, and some of the obtained mechanical properties were compared. It was observed that the electrospun CCP-PLA nanofibre composites show improved mechanical properties, and some of these mechanical properties using both techniques compared favourably well. The electrospun fibres demonstrate superior properties, mostly at 4 wt.% reinforcement. Thus, achieving good mechanical properties utilising agro waste as reinforcement in PLA to manufacture nanocomposite materials by electrospinning method is feasible and provides insight into the development of biodegradable nanocomposite materials.
Sustainable Machining of Mg-9Al-1.4Zn Foam Used for Temporary Biomedical Implant Using Cryogenic Cooling
Authors: Mohammed Abdalla , Kannan Sathish , Pervaiz Salman , Ali Shafahat , Thomas Kevin K. , Karthikeyan Ramanujam
Published: September 2022

In this study, the drilling performance of biodegradable grade Mg-9Al-1.4Zn alloy reinforced with hollow thin-walled Al2O3 microspheres is inspected under different coolant environments such as dry, Almag® mineral oil, and liquid nitrogen. Drilling experiments were carried out using titanium aluminum nitride PVD coated and uncoated K10 tools on varying volume fractions of magnesium syntactic foams (5%, 10%, and 15%) reinforced with hollow Al2O3 microspheres. Test results showed a 30–60% higher thrust force generated with liquid nitrogen drilling in comparison to dry and oil-based drilling while cutting higher volume fraction foams. Higher microsphere volume fractions of syntactic foam recorded higher machining forces, which is roughly a 200% increase as the volume fraction raised to 15%. The performance of TiAlN PVD tool coating is reflected through a reduction in thrust forces by 20% during cryogenic drilling. Scanning electron microscope (SEM) investigation of cryogenic-machined bore surfaces showed minimal drilling-induced surface defects compared to dry and Almag® mineral oil conditions. A three-dimensional, thermo-mechanical finite element-based model for drilling Mg-9Al-1.4Zn syntactic foam using AdvantEdgeTM is developed for different sustainable lubrication conditions. Surface finish (Ra) showed a 45–55% improvement during cryogenic drilling of 15% syntactic foams with minimized subsurface damages compared to dry and wet cutting conditions. The higher the volume fraction, the higher the surface roughness (Ra) and thrust force under cryogenic machining.
Structural Potting of Large Aeronautic Honeycomb Panels: End-Effector Design and Test for Automated Manufacturing
Authors: Campos Carlos , Casarejos Enrique , Segade Abraham
Published: September 2022

Structural potting is used to prepare honeycomb panels to fix metallic elements, typical in aircraft doors. In this paper, a full procedure for structural potting using robotic arms is presented for the first time. Automating this procedure requires the integration of, first, machining operations to remove the skin layers and prepare the potting points and, then, resin injection into the honeycomb cells. The paper describes the design, prototyping, and testing of specific end-effectors. Different end-effectors were explored to ensure efficient injection. The results obtained with the prototypes show that the potting quality is adequate to accomplish the required process checks for industrial manufacturing. The injection process time can be reduced by a factor greater than 3.5, together with the extra assets associated with the automation of complex tasks. Therefore, structural potting automation is demonstrated to be feasible with the end-effectors proposed for milling and injection, which are ready for use with conventional robotic arms in manufacturing lines.
A High-Performance Magnetic Shield with MnZn Ferrite and Mu-Metal Film Combination for Atomic Sensors
Authors: Fang Xiujie , Ma Danyue , Sun Bowen , Xu Xueping , Quan Wei , Xiao Zhisong , Zhai Yueyang
Published: September 2022

This study proposes a high-performance magnetic shielding structure composed of MnZn ferrite and mu-metal film. The use of the mu-metal film with a high magnetic permeability restrains the decrease in the magnetic shielding coefficient caused by the magnetic leakage between the gap of magnetic annuli. The 0.1–0.5 mm thickness of mu-metal film prevents the increase of magnetic noise of composite structure. The finite element simulation results show that the magnetic shielding coefficient and magnetic noise are almost unchanged with the increase in the gap width. Compared with conventional ferrite magnetic shields with multiple annuli structures under the gap width of 0.5 mm, the radial shielding coefficient increases by 13.2%, and the magnetic noise decreases by 21%. The axial shielding coefficient increases by 22.3 times. Experiments verify the simulation results of the shielding coefficient of the combined magnetic shield. The shielding coefficient of the combined magnetic shield is 16.5%. It is 91.3% higher than the conventional ferrite magnetic shield. The main difference is observed between the actual and simulated relative permeability of mu-metal films. The combined magnetic shielding proposed in this study is of great significance to further promote the performance of atomic sensors sensitive to magnetic field.
Incorporation of Phase Change Materials into the Surface of Aluminum Structures for Thermal Management
Authors: Anderson Christopher , Shaner Forest , Smith Walter , Luhrs Claudia
Published: September 2022

This article explores the concept of generating a porous anodic layer on the surface of a metallic component to host a phase change material (PCM) aiming to reduce the peak temperatures that the host structure will experience. The conditions to fabricate a porous anodic layer on top of an aluminum substrate were determined through varying anodization conditions: solution concentration, voltage employed, and anodization times. Pore sizes were characterized using scanning electron microscopy. The alkane n-eicosane was selected as PCM, introduced within the porous anodic annealed layer using vacuum impregnation and the thin film composite structure sealed. Epoxy resin and a metallic paste were tested as sealants. Thermal tests were performed to compare the behavior of aluminum alloy substrates anodized and sealed with and without PCM. The results showed pores with diameters in the 5–85 nm range, with average values that increased as the time of anodization was extended. The aluminum alloy impregnated with n-eicosane presents lowered surface peak temperatures during heating cycles than the samples that were only anodized or than the base alloy, demonstrating the potential of PCM incorporated in the superficial microstructure of anodic structures to manage, to a certain extent, peak transient thermal loads.
Magneto-Viscoelastic Materials: Memory Functionals and Rate Equations
Authors: Giorgi Claudio , Morro Angelo
Published: September 2022

The properties of viscoelastic solids subject to a magnetic field are modelled within two thermodynamically consistent approaches that are typical of models with a non-instantaneous response. One is based on memory functionals: the reversible changes are described by the instantaneous response, while the dissipativity is expressed by the dependence on histories. The other approach involves objective rate equations. While memory functionals lead to the difficulty of determining thermodynamically consistent free energy functionals, rate equations result in a simpler scheme. The greater simplicity allows the discovery of, in particular, models of magneto-hyperelastic materials, magneto-hypoelastic materials, and various forms of magneto-viscoelastic behaviour. The novelty of the procedure is based on two features: a representation formula, originating from the entropy inequality, and the use of the entropy production as a constitutive function. Relations with other approaches in the literature are examined in detail.
Excellent Thermoelectric Performance of 2D CuMN2 (M = Sb, Bi; N = S, Se) at Room Temperature
Authors: Fang Wenyu , Chen Yue , Kuang Kuan , Li Mingkai
Published: September 2022

2D copper-based semiconductors generally possess low lattice thermal conductivity due to their strong anharmonic scattering and quantum confinement effect, making them promising candidate materials in the field of high-performance thermoelectric devices. In this work, we proposed four 2D copper-based materials, namely CuSbS2, CuSbSe2, CuBiS2, and CuBiSe2. Based on the framework of density functional theory and Boltzmann transport equation, we revealed that the monolayers possess high stability and narrow band gaps of 0.57~1.10 eV. Moreover, the high carrier mobilities (102~103 cm2·V−1·s−1) of these monolayers lead to high conductivities (106~107 Ω−1·m−1) and high-power factors (18.04~47.34 mW/mK2). Besides, as the strong phonon-phonon anharmonic scattering, the monolayers also show ultra-low lattice thermal conductivities of 0.23~3.30 W/mK at 300 K. As results show, all the monolayers for both p-type and n-type simultaneously show high thermoelectric figure of merit (ZT) of about 0.91~1.53 at room temperature.
Early Spalling Analysis of Large Particles in High-Cr Steel during Thermal Fatigue: Relevant Mechanisms
Authors: Bombač David , Kugler Goran , Burja Jaka , Terčelj Milan
Published: September 2022

The aim of this study was to investigate the surface deterioration of high-Cr roll steel caused by the spalling of larger particles during thermal fatigue. The mechanisms of surface deterioration due to spalling of larger particles are discussed. Using a laboratory thermal fatigue test that replicates hot rolling conditions, samples were tested cyclically (up to 4500 times) at maximum cycle temperatures of 500, 600 and 700 °C, followed by water cooling. Specimens with surface deterioration were selected for analysis, revealing important influencing parameters, i.e., the combination of test temperatures, chemical composition, thermal stress and microstructural properties, leading to oxidation-assisted crack growth in different directions and consequent surface deterioration due to early spalling of larger particles. Here, we describe the mechanisms of crack propagation, especially in the lateral direction, and their relation to the subsequent spalling of larger particles, which depend on the influence of the local chemical composition on the microstructural constituents, as well as their distribution and properties. The results obtained in this study can be used in the development of roll steel microstructures with improved resistance to the identified mechanisms of surface degradation.
Enhancing Degradation Resistance of Biomedical Mg-6Zn-0.5Zr Alloy by the Incorporation of Nanodiamond
Authors: Liu Long , He Shun , Guo Zhiming , Li Jian , Zhao Mingchun , Wu Yiping
Published: September 2022

The Mg-6Zn-0.5Zr (ZK60) alloy has attracted extensive attention as one of the hopeful biomedical material candidates for bone implant applications on account of its unique degradability, favorable biocompatibility as well as mechanical compatibility. Nevertheless, the rapid degradation rate in the biological environment is the major hurdle for its clinical application in the field of bone implants. In this study, nanodiamond (ND) was incorporated into ZK60 alloy via selective laser melting technology to enhance its degradation resistance. The results showed that compared with selective laser-melted ZK60 (SLMed ZK60), the selective laser-melted ZK60 with 6 wt.% ND (SLMed ZK60−6ND) possessed the better degradation resistance with the lower degradation rate of 0.5 ± 0.1 mm/year. The enhancement of the degradation resistance was attributed to the fact that ND could promote the deposition of apatite and build up a dense and insoluble protective layer through the dissociation of the carboxyl groups on the ND surface, which could effectively hinder the further degradation of the Mg matrix. Meanwhile, the compressive strength and hardness were improved mainly due to grain refinement strengthening and ND dispersion strengthening. In addition, the SLMed ZK60−6ND possessed good cytocompatibility. These results suggested that the SLMed ZK60−6ND, with enhanced degradation resistance, improved mechanical properties, and good cytocompatibility, was an excellent biomedical material candidate for bone implant applications.
Characterization of Bond Fracture in Discrete Groove Wear of Cageless Ball Bearings
Authors: Zhao Yanling , Jin Yuan , Pan Chengyi , Wu Chuanwang , Yuan Xueyu , Zhou Gang , Han Wenguang
Published: September 2022

Cageless ball bearings with discrete grooves in the outer raceway enable the dispersion of rolling elements. Once worn, the discrete groove can cause the rolling element to discretely fail. This paper presents the discrete element method to investigate the wear of discrete grooves in cageless bearings from the standpoint of bond fracture. In conjunction with the structural characteristics of bearing races with discrete slots, we propose a hexagonal close-spaced spherical particle arrangement, in which the discrete slots are discretized into particles of the same size that are connected by bonds. The contact model and contact force equation between the rolling elements and the aggregate elements are established, and the external force on the aggregate elements is calculated. Under the influence of an external force and the arrangement of particles in the aggregate element, the internal force transfer equation of different layers and different particles is derived, and the internal force of the particles in the aggregate unit is calculated. In accordance with Hertz–Mindline theory, the bonding model of discrete groove particles is established, the size of the particle shedding cohesive force during bond fracture is determined, and the wear degree of discrete grooves is characterized by comparing the cohesive force and internal force. Numerical solutions and wear tests are combined. Bond fracture can accurately characterize the wear of discrete grooves. This approach offers theoretical guidance for cageless bearing design.
Ho-SiAlON Ceramics as Green Phosphors under Ultra-Violet Excitations
Authors: Kshetri Yuwaraj K. , Chaudhary Bina , Dhakal Dhani Ram , Lee Soo Wohn , Kim Tae-Ho
Published: September 2022

In most inorganic phosphors, increasing the concentration of activators inevitably causes the concentration quenching effect, resulting in reduced emission intensity at a high level of activator doping and the conventional practice is to limit the activator concentration to avoid the quenching. In contrast, SiAlON ceramics preserve their chemical composition over a very wide range of doping of activator ions, which favors the adjustment and optimization of the luminescence properties avoiding concentration quenching. Here, we investigate the photoluminescence properties of Ho-doped SiAlON (Ho-SiAlON) ceramics phosphors prepared by the hot-press method. Ho-SiAlON ceramics show strong green visible (554 nm) as well as infrared (2046 nm) broadband downshifting emissions under 348 nm excitation. It is shown that there is no concentration quenching, even at a very high level of Ho doping. The emission intensity of the 554 nm band increased two-fold when the Ho concentration is doubled. The results show that the Ho-SiAlON ceramics can be useful for efficient green phosphors.
Dissolution of β-C2S Cement Clinker: Part 2 Atomistic Kinetic Monte Carlo (KMC) Upscaling Approach
Authors: Izadifar Mohammadreza , Ukrainczyk Neven , Salah Uddin Khondakar Mohammad , Middendorf Bernhard , Koenders Eduardus
Published: September 2022

Cement clinkers containing mainly belite (β-C2S as a model crystal), replacing alite, offer a promising solution for the development of environmentally friendly solutions to reduce the high level of CO2 emissions in the production of Portland cement. However, the much lower reactivity of belite compared to alite limits the widespread use of belite cements. Therefore, this work presents a fundamental atomistic computational approach for comprehending and quantifying the mesoscopic forward dissolution rate of β-C2S, applied to two reactive crystal facets of (100) and (1¯00). For this, an atomistic kinetic Monte Carlo (KMC) upscaling approach for cement clinker was developed. It was based on the calculated activation energies (ΔG*) under far-from-equilibrium conditions obtained by a molecular dynamic simulation using the combined approach of ReaxFF and metadynamics, as described in the Part 1 paper in this Special Issue. Thus, the individual atomistic dissolution rates were used as input parameters for implementing the KMC upscaling approach coded in MATLAB to study the dissolution time and morphology changes at the mesoscopic scale. Four different cases and 21 event scenarios were considered for the dissolution of calcium atoms (Ca) and silicate monomers. For this purpose, the (100) and (1¯00) facets of a β-C2S crystal were considered using periodic boundary conditions (PBCs). In order to demonstrate the statistical nature of the KMC approach, 40 numerical realizations were presented. The major findings showed a striking layer-by-layer dissolution mechanism in the case of an ideal crystal, where the total dissolution rate was limited by the much slower dissolution of the silicate monomer compared to Ca. The introduction of crystal defects, namely cutting the edges at two crystal boundaries, increased the overall average dissolution rate by a factor of 519.
Influence of Heat Treatment on Microstructure, Mechanical Property, and Corrosion Behavior of Cold-Sprayed Zn Coating on Mg Alloy Substrate
Authors: Zhou Zhenpeng , Chen Xiao , Hu Xiaozhen , Li Sheng , Lv Menglong , Xie Yiting , Yao Hailong , Wang Hongtao , Bai Xiaobo
Published: September 2022

The influence of post-process heat treatment on cold-sprayed Zn coatings on the Mg alloy substrate was investigated at different temperatures (150, 250, and 350 °C) and times (2, 8, and 16 h). Phase, microstructure, microhardness, and tensile strength of Zn coatings were analyzed before and after heat treatment. Corrosion properties of Zn coatings after heat treatment were investigated in simulated body fluid by using potentiodynamic polarization and immersion testing. Results show that although the heat treatment presented little effect on phase compositions of Zn coatings, the full width at half maxima of the Zn phase decreased with the heat temperature and time. Zn coatings presented comparable microstructures before and after heat treatment in addition to the inter-diffusion layers, and the inter-diffusion layer was dependent on the heat temperature and time. Both the thickness and the microhardness of inter-diffusion layers were increased with the heat temperature and time, with the largest thickness of 704.1 ± 32.4 μm and the largest microhardness of 323.7 ± 104.1 HV0.025 at 350 °C for 2 h. The microhardness of Zn coating was significantly decreased from 70.8 ± 5.6 HV0.025 to 43.9 ± 12.5 HV0.025, with the heat temperature from the ambient temperature to 350 °C, and was slightly decreased with the heat time at 250 °C. Although the tensile strength of Zn coating was slightly increased by heat treatment, with the highest value of 40.9 ± 3.9 MPa at 150 °C for 2 h, excessive heat temperature and time were detrimental to the tensile strength, with the lowest value of 6.6 ± 1.6 MPa at 350 °C for 2 h. The heat temperature and heat time presented limited effects on the corrosion current and corrosion ratio of the Zn coatings, and Zn coatings before and after heat treatment effectively hindered the simulated body fluid from penetrating into the substrate. The corrosion behavior of Zn coatings was discussed in terms of corrosion products and microstructures after immersion.
Incremental Numerical Approach for Modeling the Macroscopic Viscoelastic Behavior of Fiber-Reinforced Composites Using a Representative Volume Element
Authors: Gort Nicolas , Zhilyaev Igor , Brauner Christian
Published: September 2022

The objective of this study is to describe the stress relaxation behavior of an epoxy-based fiber-reinforced material. An existing incremental formulation of an orthotropic linear viscoelastic material behavior was adapted to Voigt notation and to the special case of an isotropic material. Virtual relaxation tests on a representative volume element were performed, and the behavior of individual components of the relaxation tensor of the transversely isotropic composite material was determined. The study demonstrated that in the case of only one viscoelastic material, each component of the relaxation tensor can be described in terms of a scalar form factor and the behavior of the neat resin. The developed method was implemented in an incremental finite element model (FEM) analysis to calculate the stress relaxation on the macroscopic ply level. A validation of the approach has shown a promising agreement up to a limit below the glass transition temperature of 15 °C in longitudinal and 35 °C in transverse direction. This study therefore demonstrates a novel way to incrementally describe the macroscopic viscoelastic behavior of materials with a single viscoelastic component with good controllability for engineering purposes.
Tuning the Hydration Acceleration Efficiency of Calcium Carbonate by Pre-Seeding with Calcium Silicate Hydrate
Authors: Yan Han , Zhou Dongliang , Yang Yong , Shu Xin , Yu Cheng , Ran Qianping
Published: September 2022

Nanomaterials are promising candidates for refined performance optimization of cementitious materials. In recent years, numerous studies about the performance improvement of nanomaterials using polymers have been conducted, but the modification of cement-oriented nanomaterials with inorganic modifiers is seldom assessed. In this study, we explored the performance tuning and optimization of nanomaterials by inorganic modification. In this work, hydration acceleration efficiency of calcium carbonate (CaCO3, CC) was tuned via surface deposition with calcium silicate hydrate (C–S–H) nanogel through seeding. Multiple calcium carbonate–calcium silicate hydrate (CC–CSH) samples with varying degrees of surface modification were prepared via dosage control. According to characterizations, the degree of C–S–H modification on the CaCO3 surface has a maximum that is controlled by available surface space. Once the available space is depleted, excessive C–S–H turns into free form and causes adhesion between CC–CSH particles. The resultant CC–CSH samples in this work showed enhanced hydration acceleration efficiency that is tuned by the actual degree of C–S–H modification. Elevated C–S–H modification causes CC–CSH’s acceleration behavior to shift to enhanced early-age acceleration. According to mortar strength tests, CC–CSH with 5% C–S–H modification showed the most balanced performance, while CC–CSH with higher C–S–H modification showed faster early-age strength development at the cost of lower later-age strength. The inferior later-age strength of highly C–S–H-modified CC–CSH samples may be due to the coarsening of hydration products and stiffening of their network, as well as agglomeration caused by C–S–H adhesion. This study may offer a novel route for performance tuning of cement-oriented nanomaterials.
A SARS-CoV-2 Fractional-Order Mathematical Model via the Modified Euler Method
Authors: Haq Ihtisham Ul , Yavuz Mehmet , Ali Nigar , Akgül Ali
Published: September 2022

This article develops a within-host viral kinetics model of SARS-CoV-2 under the Caputo fractional-order operator. We prove the results of the solution’s existence and uniqueness by using the Banach mapping contraction principle. Using the next-generation matrix method, we obtain the basic reproduction number. We analyze the model’s endemic and disease-free equilibrium points for local and global stability. Furthermore, we find approximate solutions for the non-linear fractional model using the Modified Euler Method (MEM). To support analytical findings, numerical simulations are carried out.
Secondary Hemophagocytic Syndrome in a Patient with Plasma Cell Myeloma and CNS Involvement Treated with Lenalidomide
Authors: Milczarek Sławomir , Kulig Piotr , Baumert Bartłomiej , Łanocha Aleksandra , Sommerfeld Krzysztof , Borowiecka Ewa , Osękowska Bogumiła , Paczkowska Edyta , Zdziarska Barbara , Machaliński Bogusław
Published: September 2022

We present an extremely rare case report of a 29-year-old multiple myeloma patient with central nervous system involvement and secondary hemophagocytic lymphohistiocytosis (HLH). We observed that HLH was presumably triggered by the immunomodulatory drug—lenalidomide. HLH is frequently misdiagnosed or underdiagnosed. As HLH requires immediate treatment, our report emphasizes the need to consider HLH in the differential diagnosis when the condition of a patient receiving chemotherapy rapidly deteriorates and an infectious etiology is excluded. We furthermore discuss the pathogenesis of HLH, with particular emphasis on drugs affecting the immune system as well as possible therapeutic strategies.
Aseptic Abscess Syndrome in Rheumatoid Arthritis Patient
Authors: Owczarczyk-Saczonek Agnieszka , Kasprowicz-Furmańczyk Marta , Kuna Jakub , Klimek Paulina , Krajewska-Włodarczyk Magdalena
Published: September 2022

Aseptic abscess syndrome (AAS) is a rare, potentially life-threatening disorder, with numerous features of neutrophilic dermatoses. The main symptoms include aseptic abscess-like collections in internal organs (spleen, liver, lungs), lack of microbes (bacteria, viruses, or parasites) after an exhaustive search, ineffectiveness of antibiotics, and high sensitivity to corticosteroid therapy. AAS is characterized by the development of deep, inflammatory abscesses and systemic symptoms (weight loss, abdominal pain, fever, and leukocytosis). They may be associated with inflammatory bowel disease (IBD) and autoimmune diseases. The patient in this study is a 67-year-old man, suffering from rheumatoid arthritis (RA), with numerous purulent abscesses in the mediastinum, within the subcutaneous tissue above the extension surfaces of the joints, and on the dorsum of the hands. The lesions are accompanied by bone destruction. The patient was treated with prednisone 40 mg and adalimumab, which resulted in a quick reduction of inflammatory markers and clinical improvement, as well as the healing and absorption of abscesses. Despite COVID-19 infection, treatment with remdesivir, prednisone, and adalimumab was continued, with the complete resolution of the lesions. AAS is difficult to recognize, so practitioners have to be aware of this condition, especially in patients with RA.
A Lagrange–Laplace Integration Scheme for Weather Prediction and Climate Modelling
Authors: Lynch Peter
Published: September 2022

A time integration scheme based on semi-Lagrangian advection and Laplace transform adjustment has been implemented in a baroclinic primitive equation model. The semi-Lagrangian scheme makes it possible to use large time steps. However, errors arising from the semi-implicit scheme increase with the time step size. In contrast, the errors using the Laplace transform adjustment remain relatively small for typical time steps used with semi-Lagrangian advection. Numerical experiments confirm the superior performance of the Laplace transform scheme relative to the semi-implicit reference model. The algorithmic complexity of the scheme is comparable to the reference model, making it computationally competitive, and indicating its potential for integrating weather and climate prediction models.
PZT-Film-Based Piezoelectric Micromachined Ultrasonic Transducer with I-Shaped Composite Diaphragm
Authors: Yu Qing , Fan Guoxiang , Ren Wei , Fan Qingqing , Ti Jinming , Li Junhong , Wang Chenghao
Published: September 2022

We proposed a PZT-film-based piezoelectric micromachined ultrasonic transducer (pMUT) with an I-shaped composite diaphragm to improve the sensitivity and resonant frequency of pMUTs with the same diaphragm area. The finite element method (FEM) simulation results indicated that the pMUT with an I-shaped composite diaphragm had relatively high sensitivity and resonant frequency. The pMUT with an I-shaped diaphragm had a 36.07% higher resonant frequency than a pMUT with a circular diaphragm. The pMUT with an I-shaped diaphragm had a 3.65 dB higher loop gain (loss) than a pMUT with a rectangular diaphragm. The piezoelectric layer thickness of the pMUT with an I-shaped composite diaphragm was then optimized. Maximum loop gain (loss) was reached when the piezoelectric layer thickness was 8 μm. The pMUT with an I-shaped composite diaphragm was fabricated using the MEMS method, and its performance was evaluated.
Design and Implementation of Low-Voltage Tunable Capacitive Micro-Machined Transducers (CMUT) for Portable Applications
Authors: Goel Chirag , Cicek Paul-Vahe , Robichaud Alexandre
Published: September 2022

Capacitive micromachined ultrasonic transducers (CMUT) are MEMS-based transducers with advantages over conventional ultrasonic transducers, such as their small size, the ease of integration with semiconductor electronics, and batch fabrication. In this study, the effect of different membrane topologies on the displacement, resonant frequency, and output pressure of the CMUT membrane is investigated in the transmission mode in an air environment. A novel structural-support feature, the rocker stem, is introduced, where the membrane is weakly held to the substrate in order to minimize mechanical constraints. Four different CMUT topologies are designed and assessed to analyze the impacts of topological variations. A new CMUT array configuration is also designed to provide an approach for maximizing CMUT density. This study aims to contribute to efficient CMUT design and the determination of optimum structural parameters for portable applications in air.
Terahertz Rectangular Waveguides by UV-LIGA with Megasonic Agitation
Authors: Li Yongtao , Wang Yi , Li Hanyan , Jiang Bai , Bai Fan , Feng Jinjun
Published: September 2022

This paper researches the fabrication of a WR2.8 terahertz rectangular waveguide operating at the frequency ranging from 260 GHz to 400 GHz via UV-LIGA technology (UV-lithography, electroplating, and molding). In the process, megasonic agitation is applied to improve the mechanical properties and internal surface roughness of the WR2.8 rectangular waveguide. The effects of process parameters on the properties of structures are discussed, and optimized parameters are obtained to achieve accurate geometry dimensions. In addition, the highly crosslinked SU-8 is reliably removed from structures without damage through a synthesis method. The accuracy of the height and width of the WR2.8 rectangular waveguide is 5 µm and 2 µm, respectively, and the measured internal surface roughness is 79.6 nm. Moreover, experimental measurements and numerical simulations of the waveguide are conducted, and the difference between the two is also highlighted.
Coupled Double Closed-Loop Control for an MEMS Resonant Accelerometer
Authors: Liu Heng , Wu Jiale , Zhang Yu
Published: September 2022

There is mutual coupling between amplitude control and frequency tracking control in the closed-loop control of micromechanical resonant sensors, which restricts sensor performance. This paper introduces the principle of an in-plane vibration micromechanical resonant accelerometer with electrostatic stiffness. The characteristic parameters of the microaccelerometer were obtained through computer-aided dimension measurement and an open-loop frequency sweep test of the fabricated microstructure. An accurate numerical model was established based on the accelerometer’s dynamic principle and characteristic parameters. We established the double closed-loop driving analysis model of amplitude automatic gain control and resonant frequency phase-locked tracking. We used the averaging method to analyze the steady-state equilibrium point and the stable condition. We concluded that the integral coefficient can improve the startup overshoot when the amplitude automatic gain control loop satisfies the stability condition. Under the constraint of frequency tracking, the sizeable coefficient of the integrator can improve the system instability of the amplitude control loop. The theoretical analysis and simulation were helpful in the design and debugging of the system circuit.
A Critical Review on the Junction Temperature Measurement of Light Emitting Diodes
Authors: Cengiz Ceren , Azarifar Mohammad , Arik Mehmet
Published: September 2022

In the new age of illumination, light emitting diodes (LEDs) have been proven to be the most efficient alternative to conventional light sources. Yet, in comparison to other lighting systems, LEDs operate at low temperatures while junction temperature (Tj) is is among the main factors dictating their lifespan, reliability, and performance. This indicates that accurate measurement of LED temperature is of great importance to better understand the thermal effects over a system and improve performance. Over the years, various Tj measurement techniques have been developed, and existing methods have been improved in many ways with technological and scientific advancements. Correspondingly, in order to address the governing phenomena, benefits, drawbacks, possibilities, and applications, a wide range of measurement techniques and systems are covered. This paper comprises a large number of published studies on junction temperature measurement approaches for LEDs, and a summary of the experimental parameters employed in the literature are given as a reference. In addition, some of the corrections noted in non-ideal thermal calibration processes are discussed and presented. Finally, a comparison between methods will provide the readers a better insight into the topic and direction for future research.
NFV/SDN as an Enabler for Dynamic Placement Method of mmWave Embedded UAV Access Base Stations
Authors: Tran Gia Khanh , Ozasa Masanori , Nakazato Jin
Published: September 2022

In the event of a major disaster, base stations in the disaster area will cease to function, making it impossible to obtain life-saving information. Therefore, it is necessary to provide a wireless communication infrastructure as soon as possible. To cope with this situation, we focus on NFV/SDN (Network Function Virtualization/Software-Defined Networking)-enabled UAVs equipped with a wireless communication infrastructure to provide services. The access link between the UAV and the user is assumed to be equipped with a millimeter-wave interface to achieve high throughput. However, the use of millimeter-waves increases the effect of attenuation, making the deployment of UAVs problematic. In addition, if multiple UAVs are deployed in a limited frequency band, co-channel interference will occur between the UAVs, resulting in a decrease in the data rate. Therefore, in this paper, we propose a method that combines UAV placement and frequency division for a non-uniform user distribution in an environment with multiple UAVs. As a result, it is found that the offered data rate is improved by using our specific placement method, in terms of not only the average but also the outage user rate.
Association of Visceral Fat Area and Hyperuricemia in Non-Obese US Adults: A Cross-Sectional Study
Authors: Li Zhiying , Gao Lijie , Zhong Xiaoqing , Feng Guanrui , Huang Fengqiu , Xia Sujian
Published: September 2022

This study aimed to investigate the relationship between visceral fat area (VFA) and hyperuricemia (HUA) among non-obese adults. We extracted data from 6224 US adults aged 20–59 years from the National Health and Nutrition Examination Survey (NHANES) from 2011–2018. The VFA was divided into four quartiles (Q1–Q4). We used multivariable logistic regression models to control for known confounders. A generalized additive model (GAM) and restricted cubic spines were used to examine the association between VFA and HUA stratified by sex, and a two-piecewise linear regression model was used to calculate the threshold effect among males. The results revealed that the prevalence of HUA was 11.8% (men 15.8%, women 7.2%). In the fully adjusted model, there was a positive association between VFA and HUA [as a quartile variable, Q4 vs. Q1, odds ratio (OR): 3.77 and 95% confidence interval (CI): (2.47~5.75), p < 0.001, p for trend < 0.001; as a continuous variable, per 10 cm2 increment, OR (95%CI):1.10(1.07,1.14), p < 0.001]. Besides, this positive association remained significantly stratified by sex. Interestingly, we observed a nonlinear dose-response relationship between VFA and HUA in males (inflection point: 107.46 cm2). In conclusion, our study confirmed a significant positive relationship between VFA and HUA among non-obese adults and remained statistically significant when stratified by sex.
Intermittent Fasting—A Healthy Dietary Pattern for Diabetic Nephropathy
Authors: Yang Ming , Chen Wei , He Liyu , Liu Di , Zhao Li , Wang Xi
Published: September 2022

Diabetic nephropathy (DN), a metabolic disease, is characterized by severe systemic metabolic disorders. A unique dietary pattern, such as intermittent fasting (IF) has shown promising protective effects on various metabolic diseases, such as diabetes and cardiovascular and nervous system diseases. However, its role in regulating kidney disease, especially in DN, is still being investigated. Here, we summarize the current research progress, highlighting the relationship between IF and the risk factors for the progression of DN, and discuss the potential mechanisms by which IF improves renal injury in DN. Finally, we propose IF as a potential strategy to prevent and delay DN progression. Abbreviation: DN: Diabetic nephropathy; IF: Intermittent fasting; CPT1A: Carnitine palmitoyltransferase 1A; L-FABP: Liver-type fatty acid-binding protein; STZ: Streptozotocin; LDL: Low-density lipoproteins; HIIT: High-intensity interval training; CKD: Chronic kidney disease; ACEI: Angiotensin-converting enzyme inhibitors; ARB: Angiotensin receptor blockers; MDA: Malondialdehyde; mtDNA: Mitochondrial DNA; UCP3: Uncoupling protein-3; MAM: Mitochondria-associated endoplasmic reticulum membrane; PBMCs: Peripheral blood mononuclear cells; ERK1/2: Extracellular signal-regulated kinase 1/2; DRP1: Dynamin-related protein 1; β-HB: β-Hydroxybutyrate; AcAc: Acetoacetate; GEO: Gene Expression Omnibus; NCBI: National Center for Biotechnology Information; mTORC1: Mechanistic target of rapamycin complex 1; HMGCS2: 3-Hydroxy-3-methylglutaryl-CoA synthase 2; GSK3β: Glycogen synthase kinase 3β; AKI: Acute kidney injury; CMA: Chaperone-mediated autophagy; FGF21: Fibroblast growth factor 21.
Changes in Eating Behaviors Following Taste Education Intervention: Focusing on Children with and without Neurodevelopmental Disorders and Their Families: A Randomized Controlled Trial
Authors: Thorsteinsdottir Sigrun , Njardvik Urdur , Bjarnason Ragnar , Olafsdottir Anna S.
Published: September 2022

Fussy-eating children often display problematic behaviors around mealtimes, such as irritation, opposition, or may even throw tantrums. This may lead to reduced food variety and poor nutritional profiles, which may increase parents’ worries about their children’s diet, particularly when the children also have neurodevelopmental disorders (ND) such as Autism Spectrum Disorder (ASD) and Attention-Deficit/Hyperactive Disorder (ADHD). To investigate the effect of Taste Education on problematic mealtime behaviors, 81 children aged 8–12 years, with ND (n = 33) and without (n = 48), and their parents, participated in a 7-week Taste Education intervention. Children were matched on age, sex, and ND, and allocated at random into Immediate-intervention and Delayed-intervention groups. Parents completed the Meals in Our Household Questionnaire (MiOH). To examine changes in MiOH-scores, repeated-measures analysis-of-variance with time-points were used, with condition as factors (Immediate intervention and Delayed intervention). Baseline measures were adjusted for, and a robust linear mixed-model was fitted. Results showed superior outcomes for Intervention compared to waiting on all measures of MiOH, with stable effects through six-month follow-up. Differences were non-significant between children with and without ND. The Taste Education program suggests a promising, simple, and non-intrusive way to reduce children’s problematic mealtime behaviors in the long term.
Nutritional Composition and Bioactive Compounds of Native Brazilian Fruits of the Arecaceae Family and Its Potential Applications for Health Promotion
Authors: Morais Rômulo Alves , Teixeira Gerson Lopes , Ferreira Sandra Regina Salvador , Cifuentes Alejandro , Block Jane Mara
Published: September 2022

The fruits from the Arecaceae family, although being rich in bioactive compounds with potential benefits to health, have been underexplored. Studies on their composition, bioactive compounds, and effects of their consumption on health are also scarce. This review presents the composition of macro- and micronutrients, and bioactive compounds of fruits of the Arecaceae family such as bacaba, patawa, juçara, açaí, buriti, buritirana, and butiá. The potential use and reported effects of its consumption on health are also presented. The knowledge of these underutilized fruits is important to encourage production, commercialization, processing, and consumption. It can also stimulate their full use and improve the economy and social condition of the population where these fruits are found. Furthermore, it may help in future research on the composition, health effects, and new product development. Arecaceae fruits presented in this review are currently used as raw materials for producing beverages, candies, jams, popsicles, ice creams, energy drinks, and edible oils. The reported studies show that they are rich in phenolic compounds, carotenoids, anthocyanins, tocopherols, minerals, vitamins, amino acids, and fatty acids. Moreover, the consumption of these compounds has been associated with anti-inflammatory, antiproliferative, antiobesity, and cardioprotective effects. These fruits have potential to be used in food, pharmaceutical, and cosmetic industries. Despite their potential, some of them, such as buritirana and butiá, have been little explored and limited research has been conducted on their composition, biological effects, and applications. Therefore, more detailed investigations on the composition and mechanism of action based on in vitro and/or in vivo studies are needed for fruits from the Arecaceae family.
Resveratrol and FGF1 Synergistically Ameliorates Doxorubicin-Induced Cardiotoxicity via Activation of SIRT1-NRF2 Pathway
Authors: Lu Guangping , Liu Qingbo , Gao Ting , Li Jiahao , Zhang Jingjing , Chen Ou , Cao Cong , Mao Min , Xiao Mengjie , Zhang Xiaohui , Wang Jie , Guo Yuanfang , Tang Yufeng , Gu Junlian
Published: September 2022

Doxorubicin (DOX) has received attention due to dose-dependent cardiotoxicity through abnormal redox cycling. Native fibroblast growth factor 1 (FGF1) is known for its anti-oxidative benefits in cardiovascular diseases, but possesses a potential tumorigenic risk. Coincidentally, the anti-proliferative properties of resveratrol (RES) have attracted attention as alternatives or auxiliary therapy when combined with other chemotherapeutic drugs. Therefore, the purpose of this study is to explore the therapeutic potential and underlying mechanisms of co-treatment of RES and FGF1 in a DOX-treated model. Here, various cancer cells were applied to determine whether RES could antagonize the oncogenesis effect of FGF1. In addition, C57BL/6J mice and H9c2 cells were used to testify the therapeutic potential of a co-treatment of RES and FGF1 against DOX-induced cardiotoxicity. We found RES could reduce the growth-promoting activity of FGF1. Additionally, the co-treatment of RES and FGF1 exhibits a more powerful cardio-antioxidative capacity in a DOX-treated model. The inhibition of SIRT1/NRF2 abolished RES in combination with FGF1 on cardioprotective action. Further mechanism analysis demonstrated that SIRT1 and NRF2 might form a positive feedback loop to perform the protective effect on DOX-induced cardiotoxicity. These favorable anti-oxidative activities and reduced proliferative properties of the co-treatment of RES and FGF1 provided a promising therapy for anthracycline cardiotoxicity during chemotherapy.
Crystallization Behavior of Isotactic Propene-Octene Random Copolymers
Authors: Scoti Miriam , De Stefano Fabio , Giordano Angelo , Talarico Giovanni , De Rosa Claudio
Published: September 2022

The crystallization behavior of random propene-octene isotactic copolymers (iPPC8) prepared with a homogeneous metallocene catalyst has been studied. Samples of iPPC8 with low octene content up to about 7 mol% were isothermally crystallized from the melt at various crystallization temperatures. The samples crystallize in mixtures of the α and γ forms of isotactic polypropylene (iPP). The relative amount of γ form increases with increasing crystallization temperature, and a maximum amount of γ form (fγ(max)) is achieved for each sample. The crystallization behavior of iPPC8 copolymers is compared with the crystallization from the melt of propene–ethylene, propene–butene, propene–pentene, and propene–hexene copolymers. The results show that the behavior of iPPC8 copolymers is completely different from those described in the literature for the other copolymers of iPP. In fact, the maximum amount of γ form achieved in samples of different copolymers of iPP generally increases with increasing comonomer content, while in iPPC8 copolymers the maximum amount of γ form decreases with increasing octene content. The different behaviors are discussed based on the inclusion of co-monomeric units in the crystals of α and γ forms of iPP or their exclusion from the crystals. In iPPC8 copolymers, octene units are excluded from the crystals giving only the interruption effect that shortens the length of regular propene sequences, inducing crystallization of the γ form at low octene concentrations, lower than 2 mol%. At higher octene concentration, the crystallization of the kinetically favored α form prevails.