bluuebunny/crossref_metadata_2025 huggingface dataset:
A Novel Method for the Detection of SARS-CoV-2 Based on Graphene-Impedimetric Immunosensor
Authors: Zaccariotto Gabriel C. , Silva Martin K. L. , Rocha Giovanna S. , Cesarino Ivana
Published: July 2021

Due to the SARS-CoV-2 pandemic, there has been an increase in the search for affordable healthcare devices for mass testing and rapid diagnosis. In this context, this work described a new methodology for SARS-CoV-2 detection based on an impedimetric immunosensor developed using the advantageous immobilization of antibodies in the reduced graphene oxide (rGO). The rGO was obtained by chemical synthesis from the commercial graphene oxide (GO), and the materials were morphologically, electrochemically and visually characterized. The cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques were used to evaluate the fabrication steps of the immunosensor. The electrochemical immunoassay was considered for SARS-CoV-2 spike protein RBD detection using a impedimetric immunosensor and redox couple ([(Fe(CN)6)]3−/4−) as a probe. The immunosensor was effectively developed and applied in the detection of SARS-CoV-2 spike protein RBD in saliva samples.
Preparation and Characterization of Narrow Size Distribution PMSQ Microspheres for High-Frequency Electronic Packaging
Authors: Meng Guodong , Li Yimeng , Wang Zhengdong , Pan Cheng , Gao Wenwu , Cheng Yonghong
Published: July 2021

Polymethylsilsesquioxane (PMSQ) has become a kind of widely studied filler used in the electronic circuit board substrates due to its organic–inorganic hybrid structure, low dielectric constant, and good thermal stability, among other factors. Herein, the PMSQ microspheres were prepared by a two-step acid–base-catalyzed sol–gel method; the influences of reaction conditions including the ratio of water/methyltrimethoxysilane (MTMS), reaction temperature, concentration of the catalyst, and stirring time were systematically investigated; and the optimized reaction condition was then obtained towards a narrow particle size distribution and good sphericity. The microstructure of PMSQ microspheres was analyzed by the infrared spectrum and X-ray diffraction (XRD), which indicated that the as-prepared PMSQ had a ladder-dominant structure. The thermogravimetric analysis (TGA) demonstrated an excellent thermal stability of as-prepared PMSQ microspheres. More specifically, the dielectric constants at high frequency (1~20 GHz) of as-prepared PMSQ microspheres were measured to be about 3.7, which turned out a lower dielectric constant compared to SiO2 powder (≈4.0). This study paves the way to further improve the performance of the electronic circuit board substrates for the application of high-frequency electronic packaging.
Comparative Study on High Strain Rate Fracture Modelling Using the Application of Explosively Driven Cylinder Rings
Authors: Becker Marvin , De Vuyst Tom , Seidl Marina , Schulte Miriam
Published: July 2021

The effect of different constitutive modelling choices is crucial under a high strain rate as encountered in ballistic applications. Natural fragmentation of explosively driven cylinder rings is chosen as a simplified example to describe the ability of numerical simulations to describe fractures. The main research interests are the importance of (i) material imperfections, (ii) the accuracy of fracture models vs. damage models, (iii) the plasticity algorithm (stress update), (iv) the introduction of a triaxiality cutoff criterion to the damage models, and (v) different constitutive models (plasticity and damage). Due to the complexity of the propagation and coalescense of multiple cracks in classical methods, smoothed-particle hydrodynamics (SPH) is used as a tailor-made method to discretise the model. An elasto-plasticity model, a damage model and an equation of state describe the material behaviour. The required material parameters are determined based on stress–strain curves from quasi-static and dynamic tests. The Johnson–Cook model, with and without a modification of the strain rate term, and the Rusinek–Klepaczko model are used to describe plasticity. These plasticity models are combined either with the Johnson–Cook, the Lemaitre, or the Dolinski–Rittel damage model and the Mie–Grüneisen equation of state. The numerical results show that (i) a random distribution of initial damage increases irregularity of cracks, and gives more realistic fragment shapes, (ii) a coupling of plasticity model and fracture criterion has only a small effect on the fracture behaviour, (iii) using an iterative plasticity solver has a positive effect on the fracture behaviour, although this effect is marginal, (iv) adding a triaxiality cutoff criterion to the damage models improves the predicted fragment masses in the numerical simulations significantly, and (v) good accordance between experiments and numerical simulations are found for the Dolinski–Rittel and Lemaitre damage model with both plasticity models.
Evaluation of the Mechanical and Biocidal Properties of Lapacho from Tabebuia Plant as a Biocomposite Material
Authors: Stepczyńska Magdalena , Pawłowska Alona , Moraczewski Krzysztof , Rytlewski Piotr , Trafarski Andrzej , Olkiewicz Daria , Walczak Maciej
Published: July 2021

The aim of this article is to discuss in detail the physicochemical properties of polylactide (PLA) reinforced by cortex fibers, which may cause bacterial mortality and increased biodegradation rates. PLA biocomposites containing cortex Lapacho fibers from Tabebuia (1–10 wt%) were prepared by extrusion and injection moulding processes. The effects of Lapacho on the mechanical and biocidal properties of the biocomposites were studied using tensile and impact tests, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), thermogravimetry (TG), and the method of evaluating the antibacterial activity of antibacterial treated according to the standard ISO 22196:2011. It also presented the effects of Lapacho on the structural properties and biodegradation rates of biocomposites. This research study provides very important results complementing the current state of knowledge about the biocidal properties of Lapacho from Tabebuia plants and about cortex-reinforced biocomposites.
Modification of Lightweight Aggregate Concretes with Silica Nanoparticles—A Review
Authors: Federowicz Karol , Techman Mateusz , Sanytsky Myroslav , Sikora Pawel
Published: July 2021

The use of lightweight concrete (LWC) for structural and non-structural applications has attracted great interest in recent years. The main benefits include reduced deadload of structural elements and generally lower production and transportation costs. However, a decrease in concrete density often leads to a decrease in strength and durability. Typically, concretes are mostly modified with mineral additives such as silica fume or fly ash. Because of the recent developments in nanotechnology, research attention has turned to the possibility of improving concrete properties with nanomaterials, i.e., nano-SiO2. However, there are still certain issues with the dosage and efficiency of nanomaterials. Therefore, in order to establish the current state of knowledge in this field, this review gathers most recent results about the performance of LWC modified with nanomaterials. The review is divided into sections about the influence of nanoparticles on the fresh properties of concrete and their influence on the mechanical and durability characteristics. The paper studies in depth the most common approach to nanomaterials in concrete technology and proposes areas for further development.
Energy Structure and Luminescence of CeF3 Crystals
Authors: Kochan Orest , Chornodolskyy Yaroslav , Selech Jarosław , Karnaushenko Vladyslav , Przystupa Кrzysztof , Kotlov Aleksei , Demkiv Taras , Vistovskyy Vitaliy , Stryhanyuk Hryhoriy , Rodnyi Piotr , Gektin Alexander , Voloshinovskii Anatoliy
Published: July 2021

The results of the calculation of the energy band structure and luminescent research of CeF3 crystals are presented. The existence of two 5d1 and 5d2 subbands of the conduction band genetically derived from 5d states of Ce3+ ions with different effective electron masses of 4.9 me and 0.9 me, respectively, is revealed. The large electron effective mass in the 5d1 subband facilitates the localization of electronic excitations forming the 4f-5d cerium Frenkel self-trapped excitons responsible for the CeF3 luminescence. The structure of the excitation spectra of the exciton luminescence peaked at 290 nm, and the defect luminescence at 340 nm confirms the aforementioned calculated features of the conduction band of CeF3 crystals. The peculiarities of the excitation spectra of the luminescence of CaF2:Ce crystals dependent on the cerium concentration are considered with respect to the phase formation possibility of CeF3.
Improved Mechanical, Anti-UV Irradiation, and Imparted Luminescence Properties of Cyanate Ester Resin/Unzipped Multiwalled Carbon Nanotubes/Europium Nanocomposites
Authors: Yang Na , Qi Xiaohua , Yang Di , Chen Mengyao , Wang Yao , Huang Linjun , Grygoryeva Olga , Strizhak Peter , Fainleib Alexander , Tang Jianguo
Published: July 2021

Cyanate ester resin (CER) is an excellent thermal stable polymer. However, its mechanical properties are not appropriate for its application, with brittle weakness, and it has poor functional properties, such as luminescence. This work innovatively combines the luminescence property and the improved mechanical properties with the inherent thermal property of cyanate ester. A novel nanocomposite, CER/uMWCNTs/Eu, with multi-functional properties, has been prepared. The results show that with the addition of 0.1 wt.% of uMWCNTs to the resin, the flexural strength and tensile strength increased 59.3% and 49.3%, respectively. As the curing process of the CER progresses, the injected luminescence signal becomes luminescence behind the visible (FBV). The luminescence intensity of CER/uMWCNTs/Eu was much stronger than that of CER/MWCNTs/Eu, and the luminescence lifetime of CER/MWCNTs/Eu and CER/uMWCNTs/Eu was 8.61 μs and 186.39 μs, respectively. FBV exhibited great potential in the embedment of photon quantum information. Therefore, it can be predicted that CER/uMWCNTs/Eu composites will not only have a wide range of applications in sensing, detection, and other aspects, but will also exhibit great potential in the embedding of photon quantum information.
Fabrication, Structure, and Thermal Properties of Mg–Cu Alloys as High Temperature PCM for Thermal Energy Storage
Authors: Sun Zheng , Zou Liyi , Cheng Xiaomin , Zhu Jiaoqun , Li Yuanyuan , Zhou Weibing
Published: July 2021

This work studied the thermophysical properties of Mg-24%Cu, Mg-31%Cu, and Mg-45%Cu (wt.%) alloys to comprehensively consider the possibility of using them as thermal energy storage (TES) phase change materials (PCMs) used at high temperatures. The microstructure, phase composition, phase change temperatures, and enthalpy of these alloys were investigated by an electron probe micro analyzer (EPMA), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The XRD and EPMA results indicated that the binary eutectic phase composed of α-Mg and Mg2Cu exists in the microstructure of the prepared Mg–Cu series alloys. The microstructure of Mg-24%Cu and Mg-31%Cu is composed of α-Mg matrix and binary eutectic phases, and Mg-45%Cu is composed of primary Mg2Cu and binary eutectic phases. The number of eutectic phases is largest in Mg-31%Cu alloy. The DSC curves indicated that the onset melting temperature of Mg-24%Cu, Mg-31%Cu, and Mg-45%Cu alloys were 485, 486, and 485 °C, and the melting enthalpies were 152, 215, and 91 J/g. Thermal expansion and thermal conductivity were also determined, revealing that the Mg–Cu alloys had a low linear thermal expansion coefficient and high thermal conductivity with respect to increasing temperatures. In conclusion, the thermal properties demonstrated that the Mg–Cu alloys can be considered as a potential PCM for TES.
Macroporosity Control by Phase Separation in Sol-Gel Derived Monoliths and Microspheres
Authors: Marques Ana C. , Vale Mário
Published: July 2021

Macroporous and hierarchically macro/mesoporous materials (mostly monoliths and microspheres) have attracted much attention for a variety of applications, such as supporting or enabling materials in chromatography, energy storage and conversion, catalysis, biomedical devices, drug delivery systems, and environmental remediation. A well-succeeded method to obtain these tailored porous materials relies on the sol-gel technique, combined with phase separation by spinodal decomposition, and involves as well emulsification as a soft template, in the case of the synthesis of porous microspheres. Significant advancements have been witnessed, in terms of synthesis methodologies optimized either for the use of alkoxides or metal–salts and material design, including the grafting or immobilization of a specific species (or nanoparticles) to enable the most recent trends in technological applications, such as photocatalysis. In this context, the evolution, in terms of material composition and synthesis strategies, is discussed in a concerted fashion in this review, with the goal of inspiring new improvements and breakthroughs in the framework of porous materials.
Stress Concentration of Endodontically Treated Molars Restored with Transfixed Glass Fiber Post: 3D-Finite Element Analysis
Authors: Borges Alexandre Luiz Souto , Grangeiro Manassés Tercio Vieira , de Andrade Guilherme Schmitt , de Melo Renata Marques , Baroudi Kusai , Silva-Concilio Laís Regiane , Tribst João Paulo Mendes
Published: July 2021

The loss of dental structure caused by endodontic treatment is responsible for a decrease in tooth resistance, which increases susceptibility to fracture. Therefore, it is important that minimally invasive treatments be performed to preserve the dental structure and increase the resistance to fracture of endodontically treated posterior teeth. To evaluate under axial loads, using the finite element method, the stress distribution in endodontically treated molars restored with both transfixed or vertical glass fiber posts (GFP) and resin composite. An endodontically treated molar 3D-model was analyzed using finite element analyses under four different conditions, class II resin composite (G1, control model), vertical glass fiber post (G2), transfixed glass fiber posts (G3) and vertical and transfixed glass fiber posts (G4). Ideal contacts were considered between restoration/resin composite and resin composite/tooth. An axial load (300 N) was applied to the occlusal surface. The resulting tensile stresses were calculated for the enamel and dentin tissue from five different viewports (occlusal, buccal, palatal, mesial and distal views). According to the stress maps, similar stress trends were observed, regardless of the glass fiber post treatment. In addition, for the G1 model (without GFP), a high-stress magnitude can be noticed in the proximal faces of enamel (7.7 to 14 MPa) and dentin (2.1 to 3.3 MPa) tissue. The use of transfixed glass fiber post is not indicated to reduce the stresses, under axial loads, in both enamel and dentin tissue in endodontically treated molar with a class II cavity.
MMAP/(PH,PH)/1 Queue with Priority Loss through Feedback
Authors: Nair Divya Velayudhan , Krishnamoorthy Achyutha , Melikov Agassi , Aliyeva Sevinj
Published: July 2021

In this paper, we consider two single server queueing systems to which customers of two distinct priorities (P1 and P2) arrive according to a Marked Markovian arrival process (MMAP). They are served according to two distinct phase type distributions. The probability of a P1 customer to feedback is θ on completion of his service. The feedback (P1) customers, as well as P2 customers, join the low priority queue. Low priority (P2) customers are taken for service from the head of the line whenever the P1 queue is found to be empty at the service completion epoch. We assume a finite waiting space for P1 customers and infinite waiting space for P2 customers. Two models are discussed in this paper. In model I, we assume that the service of P2 customers is according to a non-preemptive service discipline and in model II, the P2 customers service follow a preemptive policy. No feedback is permitted to customers in the P2 line. In the steady state these two models are compared through numerical experiments which reveal their respective performance characteristics.
Psammaceratin A: A Cytotoxic Psammaplysin Dimer Featuring an Unprecedented (2Z,3Z)-2,3-Bis(aminomethylene)succinamide Backbone from the Red Sea Sponge Pseudoceratina arabica
Authors: Youssef Diaa T. A. , Asfour Hani Z. , Shaala Lamiaa A.
Published: July 2021

Bioassay-guided partition of the extract of the Red Sea sponge Pseudoceratina arabica and HPLC purification of the active fraction gave a psammaplysin dimer, psammaceratin A (1), along with psammaplysin A (2). The dimer comprises two units of psammaplysin A (2) connected via the terminal amines with an unprecedented (2Z,3Z)-2,3-bis(aminomethylene)succinamide moiety, and it represents the first dimer to be identified among the psammaplysin family. Data from 1D- and 2D-NMR and HRMS supported the chemical structures of the compounds. Psammaceratin A (1) and psammaplysin A (2) exhibited significant growth inhibition of HCT 116, HeLa, and MBA-MB-231 cells down to 3.1 μM.
Mixture of Phlorotannin and Fucoidan from Ecklonia cava Prevents the Aβ-Induced Cognitive Decline with Mitochondrial and Cholinergic Activation
Authors: Han Hye Ju , Park Seon Kyeong , Kang Jin Yong , Kim Jong Min , Yoo Seul Ki , Kim Dae-Ok , Kim Gun-Hee , Heo Ho Jin
Published: July 2021

The anti-amnesic effect of a mixture (4:6 = phlorotannin:fucoidan from Ecklonia cava, P4F6) was evaluated on amyloid-beta peptide (Aβ)-induced cognitive deficit mice. The cognitive function was examined by Y-maze, passive avoidance, and Morris water maze tests, and the intake of the mixture (P4F6) showed an ameliorating effect on Aβ-induced learning and memory impairment. After the behavioral tests, superoxide dismutase (SOD) activity and thiobarbituric acid-reactive substances (TBARS) contents were confirmed in brain tissue, and in the results, the mixture (P4F6) attenuated Aβ-induced oxidative stress. In addition, mitochondrial activity was evaluated by mitochondrial reactive oxygen species (ROS) content, mitochondrial membrane potential (MMP), adenosine triphosphate (ATP) content, and mitochondria-mediated apoptotic signaling pathway, and the mixture (P4F6) enhanced mitochondrial function. Furthermore, the mixture (P4F6) effectively regulated tau hyperphosphorylation by regulating the protein kinase B (Akt) pathway, and promoted brain-derived neurotrophic factor (BDNF) in brain tissue. Moreover, in the cholinergic system, the mixture (P4F6) ameliorated acetylcholine (ACh) content by regulating acetylcholinesterase (AChE) activity and choline acetyltransferase (ChAT) expression in brain tissue. Based on these results, we suggest that this mixture of phlorotannin and fucoidan (P4F6) might be a substance for improving cognitive function by effectively regulating cognition-related molecules.
Sternal Bone Marrow Harvesting and Culturing Techniques from Patients Undergoing Cardiac Surgery
Authors: Kang Jimmy J. H. , Bozso Sabin J. , EL-Andari Ryaan , Moon Michael C. , Freed Darren H. , Nagendran Jayan , Nagendran Jeevan
Published: July 2021

Background: Mesenchymal stromal cells (MSCs) are the most prominent cell type used in clinical regenerative medicine and stem cell research. MSCs are commonly harvested from bone marrow that has been aspirated from patients’ iliac crest. However, the ethical challenges of finding consenting patients and obtaining fresh autologous cells via invasive extraction methods remain to be barriers to MSC research. Methods: Techniques of harvesting sternal bone marrow, isolating and culturing MSCs, MSC surface phenotyping, and MSC differentiation are described. Samples from 50 patients undergoing a sternotomy were collected, and the time taken to reach 80% confluency and cell count at the second splitting of MSC were measured. Results: MSC isolated from the sternal bone marrow of patients undergoing cardiac surgery demonstrated successful MSC surface phenotyping and MSC differentiation. The mean cell count at the time of the second split was 1,628,025, and the mean time taken to reach the second split was 24.8 days. Conclusion: Herein, we describe the first reported technique of harvesting sternal bone marrow from patients already undergoing open-chest cardiac surgery to reduce the invasiveness of bone marrow harvesting, as well as the methods of isolating, culturing, and identifying MSCs for the clinical application of constructing autologous MSC-derived biomaterials.
Clustering of Diamond Nanoparticles, Fluorination and Efficiency of Slow Neutron Reflectors
Authors: Aleksenskii Aleksander , Bleuel Markus , Bosak Alexei , Chumakova Alexandra , Dideikin Artur , Dubois Marc , Korobkina Ekaterina , Lychagin Egor , Muzychka Alexei , Nekhaev Grigory , Nesvizhevsky Valery , Nezvanov Alexander , Schweins Ralf , Shvidchenko Alexander , Strelkov Alexander , Turlybekuly Kylyshbek , Vul’ Alexander , Zhernenkov Kirill
Published: July 2021

Neutrons can be an instrument or an object in many fields of research. Major efforts all over the world are devoted to improving the intensity of neutron sources and the efficiency of neutron delivery for experimental installations. In this context, neutron reflectors play a key role because they allow significant improvement of both economy and efficiency. For slow neutrons, Detonation NanoDiamond (DND) powders provide exceptionally good reflecting performance due to the combination of enhanced coherent scattering and low neutron absorption. The enhancement is at maximum when the nanoparticle diameter is close to the neutron wavelength. Therefore, the mean nanoparticle diameter and the diameter distribution are important. In addition, DNDs show clustering, which increases their effective diameters. Here, we report on how breaking agglomerates affects clustering of DNDs and the overall reflector performance. We characterize DNDs using small-angle neutron scattering, X-ray diffraction, scanning and transmission electron microscopy, neutron activation analysis, dynamical light scattering, infra-red light spectroscopy, and others. Based on the results of these tests, we discuss the calculated size distribution of DNDs, the absolute cross-section of neutron scattering, the neutron albedo, and the neutron intensity gain for neutron traps with DND walls.
Support Effects on the Activity of Ni Catalysts for the Propane Steam Reforming Reaction
Authors: Kokka Aliki , Petala Athanasia , Panagiotopoulou Paraskevi
Published: July 2021

The catalytic performance of supported Ni catalysts for the propane steam reforming reaction was investigated with respect to the nature of the support. It was found that Ni is much more active when supported on ZrO2 or YSZ compared to TiO2, whereas Al2O3− and CeO2-supported catalysts exhibit intermediate performance. The turnover frequency (TOF) of C3H8 conversion increases by more than one order of magnitude in the order Ni/TiO2 < Ni/CeO2 < Ni/Al2O3 < Ni/YSZ < Ni/ZrO2, accompanied by a parallel increase of the selectivity toward the intermediate methane produced. In situ FTIR experiments indicate that CHx species produced via the dissociative adsorption of propane are the key reaction intermediates, with their hydrogenation to CH4 and/or conversion to formates and, eventually, to CO, being favored over the most active Ni/ZrO2 catalyst. Long term stability test showed that Ni/ZrO2 exhibits excellent stability for more than 30 h on stream and thus, it can be considered as a suitable catalyst for the production of H2 via propane steam reforming.
Tailoring Morphology and Vertical Yield of Self-Catalyzed GaP Nanowires on Template-Free Si Substrates
Authors: Fedorov Vladimir V. , Berdnikov Yury , Sibirev Nickolay V. , Bolshakov Alexey D. , Fedina Sergey V. , Sapunov Georgiy A. , Dvoretckaia Liliia N. , Cirlin George , Kirilenko Demid A. , Tchernycheva Maria , Mukhin Ivan S.
Published: July 2021

Tailorable synthesis of III-V semiconductor heterostructures in nanowires (NWs) enables new approaches with respect to designing photonic and electronic devices at the nanoscale. We present a comprehensive study of highly controllable self-catalyzed growth of gallium phosphide (GaP) NWs on template-free silicon (111) substrates by molecular beam epitaxy. We report the approach to form the silicon oxide layer, which reproducibly provides a high yield of vertical GaP NWs and control over the NW surface density without a pre-patterned growth mask. Above that, we present the strategy for controlling both GaP NW length and diameter independently in single- or two-staged self-catalyzed growth. The proposed approach can be extended to other III-V NWs.
The Anti-Samaritan Attitude as Reflected in Rabbinic Midrashim
Authors: Lehnardt Andreas
Published: July 2021

Samaritans, as a group within the ranges of ancient ‘Judaisms’, are often mentioned in Talmud and Midrash. As comparable social–religious entities, they are regarded ambivalently by the rabbis. First, they were viewed as Jews, but from the end of the Tannaitic times, and especially after the Bar Kokhba revolt, they were perceived as non-Jews, not reliable about different fields of Halakhic concern. Rabbinic writings reflect on this change in attitude and describe a long ongoing conflict and a growing anti-Samaritan attitude. This article analyzes several dialogues between rabbis and Samaritans transmitted in the Midrash on the book of Genesis, Bereshit Rabbah. In four larger sections, the famous Rabbi Me’ir is depicted as the counterpart of certain Samaritans. The analyses of these discussions try to show how rabbinic texts avoid any direct exegetical dispute over particular verses of the Torah, but point to other hermeneutical levels of discourse and the rejection of Samaritan claims. These texts thus reflect a remarkable understanding of some Samaritan convictions, and they demonstrate how rabbis denounced Samaritanism and refuted their counterparts. The Rabbi Me’ir dialogues thus are an impressive literary witness to the final stages of the parting of ways of these diverging religious streams.
Tracking of Multiple Maneuvering Random Hypersurface Extended Objects Using High Resolution Sensors
Authors: Sun Lifan , Yu Haofang , Lan Jian , Fu Zhumu , He Zishu , Pu Jiexin
Published: July 2021

With the increased resolution capability of modern sensors, an object should be considered as extended if the target extent is larger than the sensor resolution. Multiple maneuvering extended object tracking (MMEOT) uses not only measurements of the target centroid but also high-resolution sensor measurements which may resolve individual features or measurement sources. MMEOT aims to jointly estimate object number, centroid states, and extension states. However, unknown and time-varying maneuvers of multiple objects produce difficulties in terms of accurate estimation. For multiple maneuvering star-convex extended objects using random hypersurface models (RHMs) in particular, their complex maneuvering behaviors are difficult to be described accurately and handled effectively. To deal with these problems, this paper proposes an interacting multiple model Gaussian mixture probability hypothesis density (IMM-GMPHD) filter for multiple maneuvering extended object tracking. In this filter, linear maneuver models derived from RHMs are utilized to describe different turn maneuvers of star-convex extended objects accurately. Based on these, an IMM-GMPHD filtering recursive form is given by deriving new update and merging formulas of model probabilities for extended objects. Gaussian mixture components of different posterior intensities are also pruned and merged accurately. More importantly, the geometrical significance of object extension states is fully considered and exploited in this filter. This contributes to the accurate estimation of object extensions. Simulation results demonstrate the effectiveness of the proposed tracking approach—it can obtain the joint estimation of object number, kinematic states, and object extensions in complex maneuvering scenarios.
Measurement of Solar Absolute Brightness Temperature Using a Ground-Based Multichannel Microwave Radiometer
Authors: Lei Lianfa , Wang Zhenhui , Ma Yingying , Zhu Lei , Qin Jiang , Chen Rui , Lu Jianping
Published: July 2021

Ground-based multichannel microwave radiometers (GMRs) can observe the atmospheric microwave radiation brightness temperature at K-bands and V-bands and provide atmospheric temperature and humidity profiles with a relatively high temporal resolution. Currently, microwave radiometers are operated in many countries to observe the atmospheric temperature and humidity profiles. However, a theoretical analysis showed that a radiometer can be used to observe solar radiation. In this work, we improved the control algorithm and software of the antenna servo control system of the GMR so that it could track and observe the sun and we use this upgraded GMR to observe solar microwave radiation. During the observation, the GMR accurately tracked the sun and responded to the variation in solar radiation. Furthermore, we studied the feasibility for application of the GMR to measure the absolute brightness temperature (TB) of the sun. The results from the solar observation data at 22.235, 26.235, and 30.000 GHz showed that the GMR could accurately measure the TB of the sun. The derived solar TB measurements were 9950 ± 334, 10,351 ± 370, and 9217 ± 375 K at three frequencies. In a comparison with previous studies, we obtained average percentage deviations of 9.1%, 5.3%, and 4.5% at 22.235, 26.235, and 30.0 GHz, respectively. The results demonstrated that the TB of the sun retrieved from the GMR agreed well with the previous results in the literature. In addition, we also found that the GMR responded to the variation in sunspots and a positive relationship existed between the solar TB and the sunspot number. According to these results, it was demonstrated that the solar observation technique can broaden the field usage of GMR.
Multispectral Image Change Detection Based on Single-Band Slow Feature Analysis
Authors: He Youxi , Jia Zhenhong , Yang Jie , Kasabov Nikola K.
Published: July 2021

Due to differences in external imaging conditions, multispectral images taken at different periods are subject to radiation differences, which severely affect the detection accuracy. To solve this problem, a modified algorithm based on slow feature analysis is proposed for multispectral image change detection. First, single-band slow feature analysis is performed to process bitemporal multispectral images band by band. In this way, the differences between unchanged pixels in each pair of single-band images can be sufficiently suppressed to obtain multiple feature-difference images containing real change information. Then, the feature-difference images of each band are fused into a grayscale distance image using the Euclidean distance. After Gaussian filtering of the grayscale distance image, false detection points can be further reduced. Finally, the k-means clustering method is performed on the filtered grayscale distance image to obtain the binary change map. Experiments reveal that our proposed algorithm is less affected by radiation differences and has obvious advantages in time complexity and detection accuracy.
Improving GNSS-R Sea Surface Altimetry Precision Based on the Novel Dual Circularly Polarized Phased Array Antenna Model
Authors: Cui Zhen , Zheng Wei , Wu Fan , Li Xiaoping , Zhu Cheng , Liu Zongqiang , Ma Xiaofei
Published: July 2021

Antenna is one of the key payloads of the GNSS-R system, and the gain is an important performance parameter. The signal-to-noise ratio (SNR) of the received signal can be improved by increasing the gain of the GNSS-R antenna, therefore the measurement accuracy is improved. However, the antenna gain and its beam width, these two performance parameters, are contradictory. If the gain of the antenna is increased, its beam width will inevitably become narrower. This narrowed beam width will affect the width of the survey strip for the GNSS-R system, which cannot meet the requirement of the high-precision and high-spatial resolution spaceborne GNSS-R sea surface altimetry in the future. In this paper, a novel dual circularly polarized phased array antenna (NDCPPA) is proposed and investigated. First, the GNSS-R satellites currently operating in orbit are all cGNSS-R systems, which use the traditional element antenna (TEA) method for measurement. The antenna used in this method is with low gain, which limits the improvement of sea surface measurement accuracy. In response to this problem, this paper establishes an NDCPPA model of iGNSS-R measurement system based on the theory of coherent signal processing on the sea surface. This model uses the high-gain scanning beam to increase the gain of the iGNSS-R antenna without affecting its coverage area, thereby improving the sea surface altimetry precision. Second, in order to verify the gain improvement effect brought by adopting the NDCPPA model, an NDCPPA model verification prototype for iGNSS-R sea surface altimetry was designed and fabricated, and then measured in a microwave anechoic chamber. The measurement results show that, compared with the TEA method, the antenna gain of our proposed verification prototype is enhanced by 9.5 dB. And the measured and designed value of the gain of the verification prototype matches well. Third, based on the GPS L1 signal, the NDCPPA model is used to analyze the effect of improving the precision of sea surface altimetry. Compared with the TEA method, the proposed model can increase the altimetric precision of the nadir point from 7.27 m to 0.21 m, which effectively improves the performance of the iGNSS-R altimetry. The NDCPPA model proposed in this article can provide the theoretical method basis and the crucial technical support for the future high-precision and high-spatial-resolution GNSS-R sea surface altimetry verification satellite.
Seasonal InSAR Displacements Documenting the Active Layer Freeze and Thaw Progression in Central-Western Spitsbergen, Svalbard
Authors: Rouyet Line , Liu Lin , Strand Sarah Marie , Christiansen Hanne Hvidtfeldt , Lauknes Tom Rune , Larsen Yngvar
Published: July 2021

In permafrost areas, the active layer undergoes seasonal frost heave and thaw subsidence caused by ice formation and melting. The amplitude and timing of the ground displacement cycles depend on the climatic and ground conditions. Here we used Sentinel-1 Synthetic Aperture Radar Interferometry (InSAR) to document the seasonal displacement progression in three regions of Svalbard. We retrieved June–November 2017 time series and identified thaw subsidence maxima and their timing. InSAR measurements were compared with a composite index model based on ground surface temperature. Cyclic seasonal patterns are identified in all areas, but the timing of the displacement progression varies. The subsidence maxima occurred later on the warm western coast (Kapp Linné and Ny-Ålesund) compared to the colder interior (Adventdalen). The composite index model is generally able to explain the observed patterns. In Adventdalen, the model matches the InSAR time series at the location of the borehole. In Kapp Linné and Ny-Ålesund, larger deviations are found at the pixel-scale, but km or regional averaging improves the fit. The study highlights the potential for further development of regional InSAR products to represent the cyclic displacements in permafrost areas and infer the active layer thermal dynamics.
Pragmatic Micrometre to Millimetre Calibration Using Multiple Methods for Low-Coherence Interferometer in Embedded Metrology Applications
Authors: Hovell Tom , Petzing Jon , Justham Laura , Kinnell Peter
Published: July 2021

In-situ metrology utilised for surface topography, texture and form analysis along with quality control processes requires a high-level of reliability. Hence, a traceable method for calibrating the measurement system’s transfer function is required at regular intervals. This paper compares three methods of dimensional calibration for a spectral domain low coherence interferometer using a reference laser interferometer versus two types of single material measure. Additionally, the impact of dataset sparsity is shown along with the effect of using a singular calibration dataset for system performance when operating across different media.
Small-Target Complex-Scene Detection Method Based on Information Interworking High-Resolution Network
Authors: Fu Yongzhong , Li Xiufeng , Hu Zungang
Published: July 2021

The CNN (convolutional neural network)-based small target detection techniques for static complex scenes have been applied in many fields, but there are still certain technical challenges. This paper proposes a novel high-resolution small-target detection network named the IIHNet (information interworking high-resolution network) for complex scenes, which is based on information interworking processing technology. The proposed network not only can output a high-resolution presentation of a small target but can also keep the detection network simple and efficient. The key characteristic of the proposed network is that the target features are divided into three categories according to image resolution: high-resolution, medium-resolution, and low-resolution features. The basic features are extracted by convolution at the initial layer of the network. Then, convolution is carried out synchronously in the three resolution channels with information fusion in the horizontal and vertical directions of the network. At the same time, multiple utilizations and augmentations of feature information are carried out in the channel convolution direction. Experimental results show that the proposed network can achieve higher reasoning performance than the other compared networks without any compromise in terms of the detection effect.
A Preference-Driven Smart Home Service for the Elderly’s Biophilic Experience
Authors: Lee Eun-Ji , Park Sung-Jun
Published: July 2021

Smart home services (SHS) should support the positive experiences of the elderly in homes with a focus on getting closer to nature. The study identified the services preferred by the elderly through a survey on the biophilic experience-based SHS, and to discuss the configuration of the sensors and devices required to provide the service. We reorganized the biophilic experience-based SHS and related sensors and devices, focusing on our previous study, and developed a survey instrument. A preference survey was conducted on 250 adults aged 20 and older, and the SPSS program was used for a factor analysis and independent two-sample T-test. We derived six factors for biophilic experience-based SHS. Compared to other age groups, the elderly preferred services that were mainly attributed to factors such as ‘Immersion and interaction with nature’ (A), ‘Management of well-being and indoor environmental quality (IEQ)’ (B), and ‘Natural process and systems’ (F). We proposed 15 prioritized services, along with their sensor and device configurations, in consideration of service provision regarding the elderly’s preferences and universality. This study contributes to new developments in elderly-friendly smart home research by converting bio-friendly ideas into the market in the development of medical services and SHS for the elderly.
OFDMA Backoff Control Scheme for Improving Channel Efficiency in the Dynamic Network Environment of IEEE 802.11ax WLANs
Authors: Kim Youngboo , Kwon Lam , Park Eun-Chan
Published: July 2021

IEEE 802.11ax uplink orthogonal frequency division multiple access (OFDMA)-based random access (UORA) is a new feature for random channel access in wireless local area networks (WLANs). Similar to the legacy random access scheme in WLANs, UORA performs the OFDMA backoff (OBO) procedure to access the channel and decides on a random OBO counter within the OFDMA contention window (OCW) value. An access point (AP) can determine the OCW range and inform each station (STA) of it. However, how to determine a reasonable OCW range is beyond the scope of the IEEE 802.11ax standard. The OCW range is crucial to the UORA performance, and it primarily depends on the number of contending STAs, but it is challenging for the AP to accurately and quickly estimate or keep track of the number of contending STAs without the aid of a specific signaling mechanism. In addition, the one for this purpose incurs an additional delay and overhead in the channel access procedure. Therefore, the performance of a UORA scheme can be degraded by an improper OCW range, especially when the number of contending STAs changes dynamically. We first observed the effect of OCW values on channel efficiency and derived its optimal value from an analytical model. Next, we proposed a simple yet effective OBO control scheme where each STA determines its own OBO counter in a distributed manner rather than adjusting the OCW value globally. In the proposed scheme, each STA determines an appropriate OBO counter depending on whether the previous transmission was successful or not so that collisions can be mitigated without leaving OFDMA resource units unnecessarily idle. The results of a simulation study confirm that the throughput of the proposed scheme is comparable to the optimal OCW-based scheme and is improved by up to 15 times compared to the standard UORA scheme.
A Motion Artifact Correction Procedure for fNIRS Signals Based on Wavelet Transform and Infrared Thermography Video Tracking
Authors: Perpetuini David , Cardone Daniela , Filippini Chiara , Chiarelli Antonio Maria , Merla Arcangelo
Published: July 2021

Functional near infrared spectroscopy (fNIRS) is a neuroimaging technique that allows to monitor the functional hemoglobin oscillations related to cortical activity. One of the main issues related to fNIRS applications is the motion artefact removal, since a corrupted physiological signal is not correctly indicative of the underlying biological process. A novel procedure for motion artifact correction for fNIRS signals based on wavelet transform and video tracking developed for infrared thermography (IRT) is presented. In detail, fNIRS and IRT were concurrently recorded and the optodes’ movement was estimated employing a video tracking procedure developed for IRT recordings. The wavelet transform of the fNIRS signal and of the optodes’ movement, together with their wavelet coherence, were computed. Then, the inverse wavelet transform was evaluated for the fNIRS signal excluding the frequency content corresponding to the optdes’ movement and to the coherence in the epochs where they were higher with respect to an established threshold. The method was tested using simulated functional hemodynamic responses added to real resting-state fNIRS recordings corrupted by movement artifacts. The results demonstrated the effectiveness of the procedure in eliminating noise, producing results with higher signal to noise ratio with respect to another validated method.
Miniaturization of Respiratory Measurement System in Artificial Ventilator for Small Animal Experiments to Reduce Dead Space and Its Application to Lung Elasticity Evaluation
Authors: Yoshida Homare , Hasegawa Yoshihiro , Matsushima Miyoko , Sugiyama Tomoshi , Kawabe Tsutomu , Shikida Mitsuhiro
Published: July 2021

A respiratory measurement system composed of pressure and airflow sensors was introduced to precisely control the respiratory condition during animal experiments. The flow sensor was a hot-wire thermal airflow meter with a directional detection and airflow temperature change compensation function based on MEMS technology, and the pressure sensor was a commercially available one also produced by MEMS. The artificial dead space in the system was minimized to the value of 0.11 mL by integrating the two sensors on the same plate (26.0 mm × 15.0 mm). A balloon made of a silicone resin with a hardness of A30 was utilized as the simulated lung system and applied to the elasticity evaluation of the respiratory system in a living rat. The inside of the respiratory system was normally pressurized without damage, and we confirmed that the developed system was able to evaluate the elasticity of the lung tissue in the rat by using the pressure value obtained at the quasi-static conditions in the case of the ventilation in the animal experiments.
DisSAGD: A Distributed Parameter Update Scheme Based on Variance Reduction
Authors: Pan Haijie , Zheng Lirong
Published: July 2021

Machine learning models often converge slowly and are unstable due to the significant variance of random data when using a sample estimate gradient in SGD. To increase the speed of convergence and improve stability, a distributed SGD algorithm based on variance reduction, named DisSAGD, is proposed in this study. DisSAGD corrects the gradient estimate for each iteration by using the gradient variance of historical iterations without full gradient computation or additional storage, i.e., it reduces the mean variance of historical gradients in order to reduce the error in updating parameters. We implemented DisSAGD in distributed clusters in order to train a machine learning model by sharing parameters among nodes using an asynchronous communication protocol. We also propose an adaptive learning rate strategy, as well as a sampling strategy, to address the update lag of the overall parameter distribution, which helps to improve the convergence speed when the parameters deviate from the optimal value—when one working node is faster than another, this node will have more time to compute the local gradient and sample more samples for the next iteration. Our experiments demonstrate that DisSAGD significantly reduces waiting times during loop iterations and improves convergence speed when compared to traditional methods, and that our method can achieve speed increases for distributed clusters.
Public Transport Use and Satisfaction by International Students and Researchers
Authors: Monteiro Mayara Moraes , de Abreu e Silva João , Ingvardson Jesper Bláfoss , Nielsen Otto Anker , Pinho de Sousa Jorge
Published: July 2021

Travel behavior adaptations resulting from international temporary relocation is understudied, despite their increasing relevance. The scarce published literature on the subject overlooks the local contexts and ignores aspects related to the adaptation processes and motivations. This study aims to partially fill this gap by addressing the travel behavior adaptation of international students and researchers, focusing on public transport (PT) frequency of use and satisfaction. To investigate this, a Bayesian Structural Equation Model was estimated using data collected from a tailor-made online survey answered by temporary international exchange students and researchers. The model confirms that (i) travel behavior habit in the city of origin influences the residential location choice in the host city; (ii) the higher the frequency of PT use in the city of origin, the higher the PT use in the host city; (iii) the residential location in the host city affects individuals’ frequency of PT use and satisfaction; (iv) perceiving technology as helpful to move around leads to perceiving the PT system as easier to use at the beginning of the stay; (v) perceiving the PT as easier to use, leads to a higher frequency of its use and a higher level of satisfaction with the PT system.