bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic localisation of wildlife with low-cost equipment: lower sensitivity, but no loss of precision
Authors: Smith Bethany R. , Root-Gutteridge Holly , Butkiewicz Hannah , Dassow Angela , Fontaine Amy C. , Markham Andrew , Owens Jessica , Schindler Loretta , Wijers Matthew , Kershenbaum Arik
Published: December 2021

Abstract Context Synchronised acoustic recorders can be used as a non-invasive tool to detect and localise sounds of interest, including vocal wildlife and anthropogenic sounds. Due to the high cost of commercial synchronised recorders, acoustic localisation has typically been restricted to small or well funded surveys. Recently, low-cost acoustic recorders have been developed, but until now their efficacy has not been compared with higher specification recorders. Aims The present study aimed to compare the efficacy of a newly developed low-cost recorder, the Conservation at Range through Audio Classification and Localisation (CARACAL), with an established, high-end recorder, the Wildlife Acoustics Song Meter (SM). Methods Four recorders of each type were deployed in a paired set-up across five nights in Wisconsin, USA. The recordings allowed for manual identification of domestic dog (Canis familiaris), grey wolf (Canis lupus), coyote (Canis latrans) and barred owl (Strix varia) calls, and then the ability of each recorder type to detect and localise the vocalising animals was compared. Key results The CARACALs were less sensitive, detecting only 47.5% of wolf, 55% of coyote, 65% of barred owl and 82.5% of dog vocalisations detected by the paired SMs. However, when the same vocalisations were detected on both recorders, localisation was comparable, with no significant difference in the precision or maximum detection ranges. Conclusions Low-cost recording equipment can be used effectively for acoustic localisation of both wild and domestic animals. However, the lower sensitivity of the CARACALs means that a denser network of these recorders would be needed to achieve the same efficacy as the SMs. Deploying a greater number of cheaper recorders increases the labour time in the field and the quantity of data to process and store. Thus, there is a trade-off between cost and time to be considered. Implications The ability to use low-cost recorders for acoustic localisation provides new avenues for tracking, managing and researching a wide range of wildlife species. Presently, CARACALs are more suited to monitoring species that have small home ranges and high amplitude vocalisations, and for when a large time investment for in situ equipment checks and data processing is feasible.
AnchorWave: Sensitive alignment of genomes with high sequence diversity, extensive structural polymorphism, and whole-genome duplication
Authors: Song Baoxing , Marco-Sola Santiago , Moreto Miquel , Johnson Lynn , Buckler Edward S. , Stitzer Michelle C.
Published: December 2021

Significance

One fundamental analysis needed to interpret genome assemblies is genome alignment. Yet, accurately aligning regulatory and transposon regions outside of genes remains challenging. We introduce Anchored Wavefront alignment (AnchorWave), which implements a genome duplication informed longest path algorithm to identify collinear regions and performs base pair–resolved, end-to-end alignment for collinear blocks using an efficient two-piece affine gap cost strategy. AnchorWave improves the alignment under a number of scenarios: genomes with high similarity, large genomes with high transposable element activity, genomes with many inversions, and alignments between species with deeper evolutionary divergence and different whole-genome duplication histories. Potential use cases include genome comparison for evolutionary analysis of nongenic sequences and population genetics of taxa with large, repeat-rich genomes.
International students’ language socialization in an English-medium university
Authors: Soltani Behnam , Zhang Lawrence Jun
Published: December 2021

This article investigates second language socialization of three international students in a tertiary institute in New Zealand. To understand the experiences of international students, the article draws on the theoretical framework of the production of space to examine how the students experienced their new social space. The article uses multiple sources of data including video/audio recordings of the classroom interaction, field notes, interviews with the focal students/teachers/tutors/lecturers, diaries, and institutional documents to provide a thick description of students’ participation, language socialization, and identities. It does a within and across case analysis of the students’ experience to situate the learning experiences but at the same time to highlight the role of space as a participating social being in the socialization process. The concepts of language socialization and identities are reconceptualized as ever-evolving and ever-changing phenomena, whose production depends on the social conditions and relationships in the social space.
Testing the Principle of No Synonymy across levels of abstraction
Authors: Laporte Samantha , Larsson Tove , Goulart Larissa
Published: December 2021

This corpus-based study tests the Principle of No Synonymy across levels of abstraction by examining the syntactic realizations of subject extraposition (e.g.,it is important to, it seems that), and by investigating at which level(s) of formal description a difference in form also entails a difference in function. The results show that distinct pairs of form and function, i.e. constructions, can be found at different levels of abstraction, but that these constructions also subsume formal realization patterns that do not encode a difference in function. This suggests that the Principle of No Synonymy largely breaks down at low levels of formal description. The study also offers a constructional account of subject extraposition by identifying a number of subject extraposition constructions, thereby showing that this is a syntactic phenomenon that is best analyzed as a family of constructions.
Chronic Effects of Flutamide in Male Beagle Dogs
Authors: Frank Doyle , Sharpe Neal , Scott Mary Celine , Mirro Elmer , Hartman Barbara , Halliwell W. H.
Published: December 2021

Flutamide, a potent nonsteroidal antiandrogen, was administered orally to male beagle dogs for 2,3, or 4 years at doses of 10,20, or 40 mg/kg/day. At each study interval, the results of clinical pathology examinations, organ weight determinations, necropsy, and histopathologic examinations generally were similar and included atrophy of the prostate gland, testicular interstitial cell hyperplasia, and seminiferous tubular atrophy and degeneration. After 3 years of drug exposure, there were 3 dogs with testicular interstitial cell adenomas and a few dogs with 1 or more enlarged mammary gland nipples. Based upon the pharmacologic activity of flutamide, these findings were expected and considered the consequence of long-term blocking of testosterone receptors and an exaggerated compensatory response to increased secretion of luteinizing hormone. The findings of this study were consistent with other examples of dysregulated hormone stimulation of target tissues noted during the nonclinical safety assessment of flutamide. In consideration of the clinical indication of flutamide for advanced prostatic carcinoma and based upon reports of minimal flutamide-related adverse clinical responses, the findings of this study pose no concern for human risk assessment.
Interaction of excitons with Cherenkov radiation in WSe2 beyond the non-recoil approximation
Authors: Chahshouri Fatemeh , Taleb Masoud , Diekmann Florian K , Rossnagel Kai , Talebi Nahid
Published: December 2021

Cherenkov radiation (CR) from electrons propagating in materials with a high refractive index have applications in particle-detection mechanisms and could be used for high-yield coherent electron beam-driven photon sources. However, the theory of the CR has been treated up to now using the non-recoil approximation, which neglects the effect of electron deceleration in materials. Here, we report on the effect of electron-beam deceleration on the radiated spectrum and exciton-photon interactions in nm-thick WSe2 crystals. The calculation of the CR is performed by simulating the kinetic energy of an electron propagating in a thick sample using the Monto Carlo method combined with the Lienard–Wiechert retarded potential. Using this approach, we numerically investigate the interaction between the excitons and generated photons (CR) beyond the non-recoil approximation and are able to reproduce experimental cathodoluminescence spectra. Our findings pave the way for an accurate design of particle scintillators and detectors, based on the strong-coupling phenomenon.
A novel self-injection relativistic backward wave oscillator
Authors: Fan Zhiqiang , Sun Jun , Cao Yibing , Song Zhimin , Shi Yanchao , Hua Ye , Wu Ping
Published: December 2021

A novel self-injection relativistic backward wave oscillator (RBWO) has been proposed. By introducing a self-injection path into the RBWO, a small portion of the energy in the reflector can be coupled to the upstream of the reflector, and then the formed electric field in the self-injection path region can pre-modulate the passing electron beam, to promote a frequency-locking oscillation of the electron beam. The pre-modulated electron beam can be expected to enhance the beam-wave interaction and suppress parasitic mode oscillation, which is beneficial for maintaining the dominant role of the operating mode. The proposed self-injection RBWO shows great potential for improving the conversion efficiency and pulse duration time. Through particle-in-cell simulation, a microwave with a power of 10.6 GW is obtained, when the beam voltage is 1.08 MeV, and the beam current is 18.6 kA. The conversion efficiency is 53%.
Theoretical analysis and general characteristics for nonlinear vibration energy harvesters
Authors: Wu Hanxiao , Tao Zhi , Li Haiwang , Xu Tiantong , Wang Wenbin , Sun Jiamian
Published: December 2021

In this paper, we present a systematic theoretical and numerical study of the output performance of nonlinear energy harvesters. The general analytical expression of output power for systems with different combinations of nonlinear stiffness and nonlinear damping, as well as symmetrical and asymmetrical systems, have been derived based on harmonic balance method, observing compliance with numerical results. We theoretically prove that there is a limit power for all nonlinear systems which is determined exclusively by the vibrator mass, excitation acceleration, and mechanical damping. The results also indicate that for symmetrical stiffness systems, the asymmetrical damping components have no effect on the output performance. Additionally, we derived semi-analytical solutions of the matching loads and numerically investigated the influence of nonlinear coefficients on the output power with matched load. When the load matches device parameters and is much larger than the internal resistance, the equivalent time-average damping is equal to the mechanical damping. Although the matching load and output power vary with the nonlinear coefficients, the normalized power and matching resistance ratio follow a power function, named matching power line, which is independent of the structural parameters. With the improvement of the equivalent time-average short-circuit damping in the vibration range, the normalized power moves to the right end of the matching power line, and the output power approach to the limit power. These conclusions provide general characteristics of nonlinear energy harvesters, which can be used to guide the design and optimization of energy harvesters.
Modulation of persistent current in graphene quantum rings
Authors: Araújo F R V , da Costa D R , Chaves A J C , de Sousa F E B , Pereira J M
Published: December 2021

We investigate the effect of long-range impurity potentials on the persistent current of graphene quantum rings in the presence of an uniform perpendicular magnetic field. The impurity potentials are modeled as finite regions of the ring with a definite length. We show that, due to the relativistic and massless character of the charge carriers in graphene, the effect of such non-uniform potentials on the energy spectrum and on the persistent current of the rings can be reliably modeled by assuming a non-perturbed ring and including an additional phase due to the interaction of the charge carriers with the potential. In addition, the results show the presence of localized states in the impurity regions. Moreover, we show that for the case of a potential created by a p-n-p junction, the persistent current can be modulated by controlling the voltage at the junction.
Spin Torque Oscillations Triggered by In-plane Field
Authors: Arun R , Gopal R , Chandrasekar V. K. , Lakshmanan M
Published: December 2021

We study the dynamics of a spin torque nano oscillator that consists of parallelly magnetized free and pinned layers by numerically solving the associated Landau-Lifshitz-Gilbert-Slonczewski equation in the presence of a field-like torque. We observe that an in-plane magnetic field which is applied for a short interval of time ($<$1ns) triggers the magnetization to exhibit self-oscillations from low energy initial magnetization state. Also, we confirm that the frequency of oscillations can be tuned over the range $\sim$25 GHz to $\sim$72 GHz by current, even in the absence of field-like torque. We find the frequency enhancement up to 10 GHz by the presence of field-like torque. We determine the Q-factor for different frequencies and show that it increases with frequency. Our analysis with thermal noise confirms that the system is stable against thermal noise and the dynamics is not altered appreciably by it.
Neutron diffraction and ab initio studies on the fully compensated ferrimagnetic characteristics of Mn2V1−x
Co
x
Ga Heusler alloys
Authors: Midhunlal P V , Venkatesh C , Chelvane J Arout , Babu P D , Kumar N Harish
Published: December 2021

Neutron diffraction and ab initio studies were carried out on Mn2V1−x
Co
x
Ga (x = 0, 0.25, 0.5, 0.75, 1) Heusler alloys which exhibits high T
C fully compensated ferrimagnetic characteristics for x = 0.5. A combined analysis of neutron diffraction and ab initio calculations revealed the crystal structure and magnetic configuration which could not be determined from the x-ray diffraction and magnetic measurements. As reported earlier, Rietveld refinement of neutron diffraction data confirmed L21 structure for Mn2VGa and X
a structure for Mn2CoGa. The alloys with x = 0.25 and 0.5 possess L21 structure with Mn(C)–Co disorder. As the Co concentration reaches 0.75, a structural transition has been observed from disordered L21 to disordered X
a. Detailed ab initio studies also confirmed this structural transition. The reason for the magnetic moment compensation in Mn2(V1−x
Co
x
)Ga was identified to be different from that of the earlier reported fully compensated ferrimagnet (MnCo)VGa. With the help of neutron diffraction and ab initio studies, it is identified that the disordered L21 structure with antiparallel coupling between the ferromagnetically aligned magnetic moments of (Mn(A)–Mn(C)) and (V–Co) atom pairs enables the compensation in Mn2V1−x
Co
x
Ga.
Gearbox compound fault diagnosis based on a combined MSGMD–MOMEDA method
Authors: Zhang Jianqun , Zhang Qing , Qin Xianrong , Sun Yuantao , Zhang Jun
Published: December 2021

Weak fault detection is a complex and challenging task when two or more faults (i.e. a compound fault) with discordant severity occur in different parts of a gearbox. The weak fault features are prone to be submerged by the severe fault features and strong background noise, which easily lead to a missed diagnosis. To solve this problem, a novel diagnosis method combining multi-symplectic geometry mode decomposition (MSGMD) and multipoint optimal minimum entropy deconvolution adjusted (MOMEDA) is proposed for gearbox compound fault in this paper. Specifically, different fault components are separated by an improved symplectic geometry mode decomposition (SGMD), namely the MSGMD method. The weak fault features are enhanced by the MOMEDA. In the process of research, a new scheme of selecting the key parameters for MOMEDA is proposed, which is a key step in the practical application of MOMEDA. Compared with SGMD, the proposed MSGMD has two main improvements, including suppressing mode mixing and preventing the generation of pseudo-components. Compared with the original method of selecting parameters based on multipoint kurtosis, the proposed MOMEDA parameter-selecting scheme has the merits of higher accuracy and greater precision. The analysis results of two cases, of simulation and an experiment signal, reveal that the MSGMD–MOMEDA method can accurately diagnose gearbox compound fault even under strong background noise.
Preparation and tensile conductivity of carbon nanotube/polyurethane nanofiber conductive films based on the centrifugal spinning method
Authors: Luo Wei , Mei Shun-qi , Liu Teng , Yang Li-ye , Fan Ling-ling
Published: December 2021

Flexible conductive thin films have recently become a research area of focus in both academia and industry. In this study, a method of preparing nanofiber conductive films by centrifugal spinning is proposed. Polyurethane (PU) nanofiber films were prepared by centrifugal spinning as the flexible substrate film, and carbon nanotubes (CNTs) were used as the conducting medium, to obtain CNTs/PU nanofiber conductive films with good conductivity and elasticity. The effects of different CNT concentrations on the properties of the nanofiber films were investigated. It was found that the conductivity of the nanofiber conductive films was optimal when an impregnation concentration of 9% CNTs was used in the stretching process. Cyclic tensile resistance tests showed that the nanofiber conductive films have good durability and repeatability. Physical and structural property analysis of the CNT/PU conductive films indicate that the adsorption of the CNTs on the PU surface was successful and the CNTs were evenly dispersed on the surface of the matrix. Moreover, the CNTs improved the thermal stability of the PU membrane. The CNT/PU conductive films were pasted onto a human finger joint, wrist joint, and Adam’s apple to test the detection of movement. The results showed that finger bending, wrist bending, and laryngeal prominence movement all caused a change in resistance of the conductive film, with an approximately linear curve. The results indicate that the CNT/PU nanofiber conductive film developed in this study can be used to test the motion of human joints.
Recent advances of biomaterials in stem cell therapies
Authors: Xue Yonger , Baig Rafia , Dong Yizhou
Published: December 2021

Stem cells have been utilized as ‘living drugs’ in clinics for decades. Their self-renewal, differentiation, and immunomodulating properties provide potential solutions for a variety of malignant diseases and disorders. However, the pathological environment may diminish the therapeutic functions and survival of the transplanted stem cells, causing failure in clinical translation. To overcome these challenges, researchers have developed biomaterial-based strategies that facilitate in vivo tracking, functional engineering, and protective delivery of stem cells, paving the way for next-generation stem cell therapies. In this perspective, we briefly overview different types of stem cells and the major clinical challenges and summarize recent progress of biomaterials applied to boost stem cell therapies.
Facile one pot microbe-mediated in situ synthesis and antibacterial activity of reduced graphene oxide-silver nanocomposite
Authors: Patil Ashwini G
Published: December 2021

The present research deals with the development of a novel bioinspired in situ fabrication of reduced graphene oxide (rGO)-silver nanoparticle (AgNPs) nanocomposite (rGO@AgNCs) using microbes namely Pseudomonas aeruginosa (PA) and Staphylococcus aureus (SA). The fabricated rGO@AgNCs were characterized using Ultraviolet-visible (UV–Vis) spectroscopy, Fourier-transform infrared spectroscopy (FTIR), particle size analysis, polydispersity index (PDI), zeta potential analysis, energy dispersive x-ray analysis (EDAX), Raman spectroscopy, powder x-ray diffraction (PXRD), high-resolution transmission electron microscopy (HR-TEM) analysis, etc. Furthermore, the rGO@AgNCs-PA and rGO@AgNCs-SA interaction with serum protein, pH stability study, and in vitro dissolution of AgNPs were also performed. The research findings of the proposed study demonstrated the simultaneous reduction of graphene oxide (GO) and AgNPs and the formation of rGO@AgNCs in the presence of microbes. The in vitro dissolution studies of rGO@AgNCs composites showed better AgNPs dissolution with controlled release and offered remarkable matrix integrity throughout the dissolution period. The size and stability of rGO@AgNCs-PA and rGO@AgNCs-SA had no significant changes at physiological pH 7.4. A minimal decrease in the zeta potential of rGO@AgNCs was observed, which may be due to the weak interaction of nanocomposites and albumin. The antibacterial application of the synthesized nanocomposite was evaluated against a pathogenic mastitis-forming bacterium. The obtained results suggested an admirable antibacterial activity of synthesized nanocomposites against the tested microbes. This knowledge will assist the scientific fraternity in designing novel antibacterial agents with enhanced antibacterial activity against various veterinary pathogens in near future.
Group feature selection for enhancing information gain in MRI reconstruction
Authors: Chang Yuchou , Saritac Mert
Published: December 2021

Magnetic resonance imaging (MRI) has revolutionized radiology. As a leading medical imaging modality, MRI not only visualizes the structures inside the body but also produces functional imaging. However, due to the slow imaging speed constrained by magnetic resonance physics, the MRI cost is expensive, and patients may feel not comfortable in a scanner for a long time. Parallel MRI (pMRI) has accelerated the imaging speed through a sub-Nyquist sampling strategy and the missing data are interpolated by the multiple coil data acquired. Kernel learning has been used in pMRI reconstruction to learn the interpolation weights and reconstruct the undersampled data. However, noise and aliasing artifacts still exist in the reconstructed image and a large number of auto-calibration signal lines are needed. To further improve kernel-learning-based MRI reconstruction and accelerate the speed, this paper proposes a group feature selection strategy to improve the learning performance and enhance the reconstruction quality. An explicit kernel mapping is used for selecting a subset of features which contribute most to estimating the missing k-space data. The experimental results show that the learning behaviors can be better predicted and therefore the reconstructed image quality can be improved.
Noninvasive estimation of local speed of sound by pulse-echo ultrasound in a rat model of nonalcoholic fatty liver
Authors: Telichko Arsenii V , Ali Rehman , Brevett Thurston , Wang Huaijun , Vilches-Moure Jose G , Kumar Sukumar U , Paulmurugan Ramasamy , Dahl Jeremy J
Published: December 2021

Objective. Speed of sound has previously been demonstrated to correlate with fat concentration in the liver. However, estimating speed of sound in the liver noninvasively can be biased by the speed of sound of the tissue layers overlying the liver. Here, we demonstrate a noninvasive local speed of sound estimator, which is based on a layered media assumption, that can accurately capture the speed of sound in the liver. We validate the estimator using an obese Zucker rat model of non-alcoholic fatty liver disease and correlate the local speed of sound with liver steatosis. Approach. We estimated the local and global average speed of sound noninvasively in 4 lean Zucker rats fed a normal diet and 16 obese Zucker rats fed a high fat diet for up to 8 weeks. The ground truth speed of sound and fat concentration were measured from the excised liver using established techniques. Main Results. The noninvasive, local speed of sound estimates of the livers were similar in value to their corresponding ‘ground truth’ measurements, having a slope ± standard error of the regression of 0.82 ± 0.15 (R
2 = 0.74 and p < 0.001). Measurement of the noninvasive global average speed of sound did not reliably capture the ‘ground truth’ speed of sound in the liver, having a slope of 0.35 ± 0.07 (R
2 = 0.74 and p < 0.001). Decreasing local speed of sound was observed with increasing hepatic fat accumulation (approximately −1.7 m s−1 per 1% increase in hepatic fat) and histopathology steatosis grading (approximately −10 to −13 m s−1 per unit increase in steatosis grade). Local speed of sound estimates were highly correlated with steatosis grade, having Pearson and Spearman correlation coefficients both ranging from −0.87 to −0.78. In addition, a lobe-dependent speed of sound in the liver was observed by the ex vivo measurements, with speed of sound differences of up to 25 m s−1 (p < 0.003) observed between lobes in the liver of the same animal. Significance. The findings of this study suggest that local speed of sound estimation has the potential to be used to predict or assist in the measurement of hepatic fat concentration and that the global average speed of sound should be avoided in hepatic fat estimation due to significant bias in the speed of sound estimate.
Variation in isocentre location of an Elekta Unity MR-linac through full gantry rotation
Authors: Hunt James R , Ebert Martin A , Rowshanfarzad Pejman , Riis Hans L
Published: December 2021

Objective. The objective of this study was to separately quantify the stability of the megavoltage imager (MVI) and radiation head of an Elekta Unity MRL, throughout full gantry rotation. Approach. A ball-bearing (BB) phantom was attached to the radiation head of the Unity, while a single BB was placed at isocentre. Images were acquired during rotation, using the MVI. These images were processed using an in-house developed MATLAB program to reduce the errors resulted by noise, and the positions of the BBs in the images were analysed to extract MVI and radiation head sag data. Main results. The results returned by this method showed reproducibility, with a mean standard deviation of 7 μm for the position of BBs across all gantry angles. The radiation head was found to sag throughout rotation, with a maximum course of movement of 0.59 mm. The sag pattern was stable over a period greater than a year but showed some dependence on gantry rotation direction. Significance. As MRL is a relatively new system, it is promising to have data supporting the high level of precision on one Elekta Unity machine. Isolating and quantifying the sources of uncertainty in radiation delivery may allow more sophisticated analysis of how the system performance may be improved.
Automated detection of skeletal metastasis of lung cancer with bone scans using convolutional nuclear network
Authors: Li Tongtong , Lin Qiang , Guo Yanru , Zhao Shaofang , Zeng Xianwu , Man Zhengxing , Cao Yongchun , Hu Yonghua
Published: December 2021

A bone scan is widely used for surveying bone metastases caused by various solid tumors. Scintigraphic images are characterized by inferior spatial resolution, bringing a significant challenge to manual analysis of images by nuclear medicine physicians. We present in this work a new framework for automatically classifying scintigraphic images collected from patients clinically diagnosed with lung cancer. The framework consists of data preparation and image classification. In the data preparation stage, data augmentation is used to enlarge the dataset, followed by image fusion and thoracic region extraction. In the image classification stage, we use a self-defined convolutional neural network consisting of feature extraction, feature aggregation, and feature classification sub-networks. The developed multi-class classification network can not only predict whether a bone scan image contains bone metastasis but also tell which subcategory of lung cancer that a bone metastasis metastasized from is present in the image. Experimental evaluations on a set of clinical bone scan images have shown that the proposed multi-class classification network is workable for automated classification of metastatic images, with achieving average scores of 0.7392, 0.7592, 0.7242, and 0.7292 for accuracy, precision, recall, and F-1 score, respectively.
Power transport efficiency during O-X-B 2nd harmonic electron cyclotron heating in a helicon linear plasma device
1
Authors: Marin J F Caneses , Lau C L , Goulding R H , Bigelow T , Biewer T M , Caughman J B O , Rapp J
Published: December 2021

The principal objective of this work is to report on the power coupled to a tungsten target in the prototype-material plasma exposure experiment device during oblique injection of a microwave beam (<70 kW at 28 GHz) into a high-power (∼100 kW at 13.56 MHz) over-dense (

n
e

>
1
×

10

19

 

m

−
3

) deuterium helicon plasma column. The experimental setup, electron heating system, electron heating scheme, and IR thermographic diagnostic for quantifying the power transport is described in detail. It is demonstrated that the power transported to the target can be effectively controlled by adjusting the magnetic field profile. Using this method, heat fluxes up to 22 MW m−2 and power transport efficiencies in the range of 17%–20% have been achieved using 70 kW of microwave power. It is observed that most of the heat flux is confined to a narrow region at the plasma periphery. Ray-tracing calculations are presented which indicate that the power is coupled to the plasma electrons via an O-X-B mode conversion process. Calculations indicate that the microwave power is absorbed in a single pass at the plasma periphery via collisions and in the over-dense region via 2nd harmonic cyclotron resonance of the electron Bernstein wave. The impact of these results is discussed in the context of MPEX.
A macroscopic viscoelastic model of magnetorheological elastomer with different initial particle chain orientation angles based on fractional viscoelasticity
Authors: Fan Jiahao , Yao Jianfei , Yu Yang , Li Yan
Published: December 2021

In this paper, a macroscopic viscoelastic modeling method for magnetorheological elastomer (MRE) based on fractional derivative model is presented to describe the dynamic viscoelastic properties of MRE with different initial particle chain orientation angles. The angle between the particle chain and the applied magnetic field is used as an indicator to describe the directionality of the particle chain. MRE samples with different initial inclination angles have been designed and fabricated. The dynamic viscoelastic properties of different MRE samples under shear working mode were measured using a parallel plate rheometer. The dynamic viscoelastic properties of MRE with different initial inclination angles are analyzed under the test conditions of different strain amplitude, frequency and magnetic flux density. The test results show that the initial inclination angle of the particle chain in the MRE has a significant effect on the dynamic viscoelastic properties of the MRE. A polynomial function is used to describe the relationship between the initial particle chain orientation angle and the magneto-induced modulus of MRE. A phenomenological model of magneto-induced modulus is established based on the fractional derivative model. The model parameters are identified using the nonlinear least square method. The predicted values of the model are in good agreement with the experimental results, indicating that the model can well describe the dynamic viscoelastic properties of MRE.
Rotational nonlinear double-beam energy harvesting
Authors: Lu Ze-Qi , Zhang Fei-Yang , Fu Hai-Ling , Ding Hu , Chen Li-Qun
Published: December 2021

This paper presents an investigation of the performance of a coupled rotational double-beam energy harvester (DBEH) with magnetic nonlinearity. Two spring-connected cantilever beams are fixed on a rotating disc. Repelling magnets are attached to the frame and to the lower beam tip, and an equal-mass block is attached to the tip of the upper beam. To describe the dynamic response, a theoretical model related to the rotational motion of the coupled cantilever beam is derived from the Lagrange equations. In addition, the harmonic balance method, together with the arc-length continuation method, is applied to obtain the frequency response functions (FRFs). Parametric studies are then conducted to analyze the effect of varying the parameters on the energy harvesting performance, and numerical analysis is performed to validate the analytical solutions. Finally, the theoretical model is verified by forward- and reverse-frequency-sweeping experiments. The DBEH in rotational motion can perform effective energy harvesting over a wide range of rotational frequencies (10–35 rad s−1 ). The upper beam is found to exhibit better energy harvesting efficiency than the lower beam around the resonant frequency. This study effectively broadens the energy harvesting bandwidth and provides a theoretical model for the design of nonlinear magnet-coupled double-beam structure in rotational energy harvesting.
Modeling and validation of nonlinear voltage-current characteristics of ITER PF joint sample tested in the SULTAN facility
Authors: Huang J , Bagni T , Ilyin Y , Nijhuis A
Published: December 2021

The International Thermonuclear Experimental Reactor poloidal field (PF) coils are wound into double pancakes with NbTi cable-in-conduit conductors, which are connected by joints in shaking hands lap-type configuration. The coils are operating in pulsed mode with a maximum operating current of 55 kA and peak magnetic field of 6.4 T, utilizing electromagnetic load on the conductors and joints. A series of PF qualification joint samples modified in praying hands configuration is measured in the SULTAN facility. For some samples, a nonlinear voltage-current (VI) characteristic is observed during the assessment of joint resistance. The growth of joint resistance versus the B× I product is larger than what is expected from the magneto-resistant copper contribution. Two non-homogeneous contact resistance models are developed and combined to quantitatively evaluate the reason for the nonlinear VI behavior in combination with the relevant power dissipation and current redistribution in the joint. The simulations reveal that, for the particular pre-qualification PFJEU2 sample with resistance variation up to 3.5 nΩ, the most probable reason for the nonlinear VI characteristic is a widely spread defective connection between copper sole and shim. The electromagnetic force involves a separation effect on the mechanically and electrically weakly connected parts, resulting into a varying resistance depending on transport current and background field. The hypothesis and models are validated by an experiment on a similar sample PFJEU3 and a post-mortem examination of the PFJEU2 sample.
Prediction models establishment and comparison for guiding force of high-temperature superconducting maglev based on deep learning algorithms
Authors: Ke Zhihao , Liu Xiaoning , Chen Yining , Shi Hongfu , Deng Zigang
Published: December 2021

Due to the merits of self-stability and low energy consumption, high-temperature superconducting (HTS) maglev has the potential to become a novel type of transportation mode. As a key index to guarantee the lateral self-stability of HTS maglev, guiding force has strong non-linearity and is determined by multitudinous factors, and these complexities impede its further researches. Compared to traditional finite element and polynomial fitting method, the prosperity of deep learning algorithms could provide another guiding force prediction approach, but the verification of this approach is still blank. Therefore, this paper establishes five different neural network models (radial basis function, deep neural network (DNN), convolution neural network, recurrent neural network, long short-term memory neural network (LSTM)) to predict HTS maglev guiding force and compares their prediction efficiency based on 3720 pieces of collected data. Meanwhile, two adaptive iterative algorithms for the parameter matrix and learning rate adjustment are proposed, which could effectively reduce computing time and unnecessary iterations. According to the results, it is revealed that the DNN model shows the best fitting goodness, while the LSTM model displays the smoothest fitting curve on guiding force prediction. Based on this discovery, the effects of learning rate and iterations on prediction accuracy of the constructed DNN model are studied. And the learning rate and iterations at the highest guiding force prediction accuracy are 0.00025 and 90 000, respectively. Moreover, the K-fold cross-validation method is also applied to this DNN model, whose result manifests the generalization and robustness of this DNN model. The imperative of K-fold cross validation method to ensure universality of guiding force prediction model is likewise assessed. This paper firstly combines HTS maglev guiding force prediction with deep learning algorithms considering different field cooling height, real-time magnetic flux density, liquid nitrogen temperature and motion direction of bulk. Additionally, this paper gives a convenient and efficient method for HTS guiding force prediction and parameter optimization.
Stack-based grating for wideband polarization splitter in terahertz
Authors: Lin Zefan , Wang Bo , Fu Chen
Published: December 2021

A novel wideband terahertz polarization beam splitter with special diffraction orders working at terahertz band is described in this paper. The polarizer can achieve high diffraction efficiency and uniformity in the 2.50–2.56 THz band. Based on rigorous coupled-wave analysis (RCWA) and simulated annealing algorithm, we proposed an efficient algorithm to optimize the polarizer. After calculations, 98.45% single-port high-efficiency reflection for transverse electric (TE) polarization and 42.33%/42.57% highly uniform dual-port beam splitting for transverse magnetic (TM) polarization were finally obtained. In addition, through RCWA and simplified modal method, the electromagnetic field distributions of TE and TM polarizations are shown visually and described quantitatively. Moreover, the results displayed in section 3 prove that the grating possesses the characteristics of relatively large bandwidth and insensitivity to the incident angle. Therefore, the novel scheme in this paper has great reference value for the research of terahertz modulation devices and the integration of terahertz communication systems.
Mathematical analysis of two-phase blood flow through a stenosed curved artery with hematocrit and temperature dependent viscosity
Authors: Kumawat Chandan , Sharma B K , Mekheimer K S
Published: December 2021

A two-phase blood flow model is considered to analyze the fluid flow and heat transfer in a curved tube with time-variant stenosis. In both core and plasma regions, the variable viscosity model (Hematocrit and non linear temperature-dependent, respectively) is considered. A toroidal coordinate system is considered to describe the governing equations. The perturbation technique in terms of perturbation parameter ε is used to obtain the temperature profile of blood flow. In order to find the velocity, wall shear stress and impedance profiles, a second-order finite difference method is employed with the accuracy of 10−6 in the each iteration. Under the conditions of fully-developed flow and mild stenosis, the significance of various physical parameters on the blood velocity, temperature, wall shear stress (WSS) and impedance are investigated with the help of graphs. A validation of our results has been presented and comparison has been made with the previously published work and present study, and it revels the good agreement with published work. The present mathematical study suggested that arterial curvature increase the fear of deposition of plaque (atherosclerosis), while, the use of thermal radiation in heat therapies lowers this risk. The positive add in the value of λ
1 causes to increase in plasma viscosity; as a result, blood flow velocity in the stenosed artery decreases due to the assumption of temperature-dependent viscosity of the plasma region. Clinical researchers and biologists can adopt the present mathematical study to lower the risk of lipid deposition, predict cardiovascular disease risk and current state of disease by understanding the symptomatic spectrum, and then diagnose patients based on the risk.
Enhanced single-phase heat transfer performance via vortex secondary flow in hypervapotron configuration
Authors: Lim Ji Hwan , Park Minkyu
Published: December 2021

As the hypervapotron (HV) heat sink is used to cool many areas inside the fusion tokamak, it is essential to understand its heat transfer performance to calculate the thermal efficiency of the power generation system. Therefore, in this study, the single-phase (SP) heat transfer performance of HV heat sink was evaluated through sub-cooled flow boiling experiments under one-side high-heat load conditions. When vapor is generated inside the heat sink, flow instability and a potential risk of reaching the critical heat flux are created. Therefore, in commercial power plants, cooling systems tend to operate in the SP regime. System parameters that can be adjusted in the power generation system include the system pressure, mass flow rate, and subcooling, and the effect of these three parameters on the heat transfer performance in the SP regime was analyzed. It was experimentally observed that the mass flow rate was the most influential variable. The prediction performance of the SP forced convection heat transfer correlations of the existing conventiaonl channel were evaluated. The results revealed that they tended to under-predict the heat transfer performance of the HV heat sink. In addition, the same trends were found when the forced convection heat transfer correlation of the curved channel was evaluated. The reasons for the former and the latter are that the heat transfer enhancement effect by the vortex flow occurring between the fins of the HV heat sink is not reflected in the correlations, and the vortex effect of the HV heat sink is not expressed as a variable. Therefore, a new vortex forced convection heat transfer correlation was developed through the newly defined Dean number of the HV heat sink. The developed correlation recorded an average error rate of 0.48%.
Theoretical study of electronic properties and chemical stability of cubic phase zirconia nanowires
Authors: Cuevas F J L , Courel Piedrahita M , Feddi E , Rentería T V M , Ojeda M M L , Velásquez O C , Mowbray D J , Ojeda M M
Published: December 2021

Zirconia bulk is one of the most studied materials around the world due to different properties such as a high melting temperature, biocompatibility and high thermal expansion, among many others. However, there is little experimental research about Zirconia nanowires and until now there are few theoretical papers on the subject. In this work, Density Functional Theory (DFT) calculations on bare ZrO2 nanowires with diameter variation were performed. In order to get the more accurate parameters for calculation on nanowires, we employed the Murnaghan equation of state in a perfect cubic crystal of ZrO2 (c-ZrO2) and we compared the results obtained with some experimental data as well as the lattice parameter and the bulk modulus. The nanowires were grown along the [1 1 1] direction with five different diameters. All calculations were carried out by DFT implemented in SIESTA code. According to our results, the functional PBE of the Generalized Gradient Approximation (GGA-PBE) is the more accurate functional for describing the E
xc
on ZrO2. The calculation of formation and surface energies shows that these nanowires are chemically stable. Furthermore, nanowires larger than 8.78 Å present a direct band gap. These results indicate the possibility of applying ZrO2 nanowires in the optoelectronic field.
Nonlinear structures: soliton, shocklike and explosive waves in quantum semiconductor plasma
Authors: Al-Yousef Haifa A
Published: December 2021

The properties and conditions for the appearance of some nonlinear waves in a three-dimensional semiconductor plasma are discussed, by studying the described plasma fluid system with quantum gradient forces and degraded pressures. Our analytical procedure is built on the reductive perturbation theory to obtain the Kadomtsev-Petvashvili equation for the fluid model and solving it using the direct integration method and the Bäcklund transform. Through different solution methods we got different nonlinear solutions describing different pulse profiles such as soliton, kink and explosive pulses. This model can be used to identify the potential disturbances in a semiconductor plasma.
A mechanism for spin electron acoustic soliton observed in a spin-polarized nanosized electron-hole plasma
Authors: Afify M S , Iqbal Z , Murtza G
Published: December 2021

The formation and the characteristics of spin electron acoustic (SEA) soliton in a beam interacting spin-polarized electron-hole plasma are investigated. These wavepackets are supposed to be the source of heating during the excitation process. We have used the separate spin evolution-quantum hydrodynamic (SSE-QHD) model along with Maxwell equations and derived the Korteweg–de Vries (KdV) equation by using the reductive perturbation method (RPM). We note that the larger values of beam density and spin polarization can change the soliton nature from rarefactive to compressive. Our findings may be important to understand the characteristics of localized spin-dependent nonlinear waves in nanosized semiconductor devices.
Nonlinear oscillations in a constant gravitational field
Authors: Kontomaris S V , Malamou A
Published: December 2021

Exploring non-linear oscillations is a challenging task since the related differential equations cannot be directly solved in terms of elementary functions. Thus, complicated mathematical or numerical methods are usually employed to find accurate or approximate expressions that describe the behavior of the system with respect to time. In this paper, the vertical oscillations of an object under the influence of its weight and an opposite force with magnitude F = cyn, where n > 0 are being explored. Accurate and approximate simple solutions regarding the object’s position with respect to time are presented and the dependence of the oscillation’s period from the oscillation’s range of displacements and the exponent n is revealed. In addition, the special case in which n = 3/2 (which describes the oscillation of a rigid sphere on an elastic half space) is also highlighted. Lastly, it is shown that similar cases (such as the case of a force with magnitude F = kx + λ×2) can be also treated using the same approach.
Cosmology at high redshift — a probe of fundamental physics
Authors: Sailer Noah , Castorina Emanuele , Ferraro Simone , White Martin
Published: December 2021

An observational program focused on the high redshift (2<z<6) Universe has the opportunity to dramatically improve over upcoming LSS and CMB surveys on measurements of both the standard cosmological model and its extensions. Using a Fisher matrix formalism that builds upon recent advances in Lagrangian perturbation theory, we forecast constraints for future spectroscopic and 21-cm surveys on the standard cosmological model, curvature, neutrino mass, relativistic species, primordial features, primordial non-Gaussianity, dynamical dark energy, and gravitational slip. We compare these constraints with those achievable by current or near-future surveys such as DESI and Euclid, all under the same forecasting formalism, and compare our formalism with traditional linear methods. Our Python code FishLSS — used to calculate the Fisher information of the full shape power spectrum, CMB lensing, the cross-correlation of CMB lensing with galaxies, and combinations thereof — is publicly available.