bluuebunny/crossref_metadata_2025 huggingface dataset:
How good are 2D transistors? An application-specific benchmarking study
Authors: Abuzaid Hattan , Williams Nicholas X. , Franklin Aaron D.
Published: January 2021

The research community has invested heavily in semiconducting two-dimensional (2D) materials, such as transition metal dichalcogenides (TMDs). Their stability when scaled down to a few atoms thick makes them attractive candidates to replace or supplement silicon in many future technologies. Although this sentiment is prevalent, demonstrations of 2D field-effect transistors (FETs) often do not present their data in a way that enables a straightforward comparison. For example, some papers solely use mobility as the figure of merit, while others focus on unnormalized device on-current. Here, we benchmark the performance of a selection of 2D FETs with field-corrected metrics that allow a more accurate projection of their potential; while the demonstrated methods are by no means comprehensive, they provide insight into improved benchmarking of 2D FETs going forward. Importantly, we show that appropriate benchmarking requires consideration of the specific application, with the three dominant potential application areas of front-end-of-line (FEOL) high-performance FETs, back-end-of-line (BEOL) 3D-integrated FETs, and low-cost thin-film FETs (or TFTs) each demonstrated. We find that 2D materials have the potential to compete with silicon as the channel in scaled FEOL high-performance devices. Meanwhile, in BEOL applications, FETs from in situ synthesized 2D materials have performance limited by their low crystal quality – a result of the stringent thermal budget of BEOL fabrication, which necessitates the use of transferred 2D materials. In the TFT area, 2D materials are simpler to fabricate than their silicon-based counterparts and they are competitive with other material alternatives. As promising as these findings are, there remain many hurdles for 2D materials to overcome, including poor reliability, performance variability, and fabrication scalability. Continuous research effort, combined with appropriate benchmarking, is strongly encouraged.
Reversibility of non-saturated linear cellular automata on finite triangular grids
Authors: Wolnik Barbara , Augustynowicz Antoni , Dziemiańczuk Maciej , De Baets Bernard
Published: January 2021

Discrete dynamical systems such as cellular automata are of increasing interest to scientists in a variety of disciplines since they are simple models of computation capable of simulating complex phenomena. For this reason, the problem of reversibility of such systems is very important and, therefore, recurrently taken up by researchers. Unfortunately, the study of reversibility is remarkably hard, especially in the case of two- or higher-dimensional cellular automata. In this paper, we propose a novel and simple method that allows us to completely resolve the reversibility problem of a wide class of linear cellular automata on finite triangular grids with null boundary conditions.
Unsteady dynamics of wedge-induced oblique detonations under periodic inflows
Authors: Yang Pengfei , Ng Hoi Dick , Teng Honghui
Published: January 2021

Two-dimensional, wedge-induced oblique detonation waves (ODWs) subject to periodic inflow are simulated using the reactive Euler equations with a two-step induction–reaction kinetic model. The focus of this work is how the periodic unsteadiness of a sinusoidal density disturbance with varying frequency and amplitude influences an initially established ODW structure. Three fundamental ODW structures with different transition types and inflow Mach numbers are disturbed, resulting in two types of triple-point formations: the main triple point (MTP) and the train of triple points (TTP). The TTP features multi-triple points arising almost simultaneously and traveling together, which has never been observed before. A parametric study and frequency analysis reveal that the MTP derives from forced destabilization, while the TTP derives from the combined effect of surface instability and inflow disturbance. Furthermore, a new phenomenon of MTP degeneration is observed for a proper inflow Mach number and disturbance amplitude. Finally, the oscillation amplitudes of unsteady ODWs are analyzed with respect to the Mach number and inflow disturbance, demonstrating the effects of transition type on surface unsteadiness.
A primitive variable discrete exterior calculus discretization of incompressible Navier–Stokes equations over surface simplicial meshes
Authors: Jagad Pankaj , Abukhwejah Abdullah , Mohamed Mamdouh , Samtaney Ravi
Published: January 2021

A conservative primitive variable discrete exterior calculus (DEC) discretization of the Navier–Stokes equations is performed. An existing DEC method [M. S. Mohamed, A. N. Hirani, and R. Samtaney, “Discrete exterior calculus discretization of incompressible Navier–Stokes equations over surface simplicial meshes,” J. Comput. Phys. 312, 175–191 (2016)] is modified to this end and is extended to include the energy-preserving time integration and the Coriolis force to enhance its applicability to investigate the late-time behavior of flows on rotating surfaces, i.e., that of the planetary flows. The simulation experiments show second order accuracy of the scheme for the structured-triangular meshes and first order accuracy for the otherwise unstructured meshes. The method exhibits a second order kinetic energy relative error convergence rate with mesh size for inviscid flows. The test case of flow on a rotating sphere demonstrates that the method preserves the stationary state and conserves the inviscid invariants over an extended period of time.
Effective structure of a system with continuous polydispersity
Authors: Patel Palak , Nandi Manoj Kumar , Nandi Ujjwal Kumar , Maitra Bhattacharyya Sarika
Published: January 2021

In a system of N particles, with continuous size polydispersity, there exists an N(N − 1) number of partial structure factors, making it analytically less tractable. A common practice is to treat the system as an effective one component system, which is known to exhibit an artificial softening of the structure. The aim of this study is to describe the system in terms of M pseudospecies such that we can avoid this artificial softening but, at the same time, have a value of M ≪ N. We use potential energy and pair excess entropy to estimate an optimum number of species, M0. We then define the maximum width of polydispersity, Δσ0, that can be treated as a monodisperse system. We show that M0 depends on the degree and type of polydispersity and also on the nature of the interaction potential, whereas Δσ0 weakly depends on the type of polydispersity but shows a stronger dependence on the type of interaction potential. Systems with a softer interaction potential have a higher tolerance with respect to polydispersity. Interestingly, M0 is independent of system size, making this study more relevant for bigger systems. Our study reveals that even 1% polydispersity cannot be treated as an effective monodisperse system. Thus, while studying the role of polydispersity by using the structure of an effective one component system, care must be taken in decoupling the role of polydispersity from that of the artificial softening of the structure.
Improved thermoelectric performance of GeTe via efficient yttrium doping
Authors: Gao Weihong , Liu Zihang , Zhang Wenhao , Sato Naoki , Guo Quansheng , Mori Takao
Published: January 2021

Optimization of the carrier concentration by doping/alloying is a key prerequisite for improving thermoelectric performance. In reality, it is, however, challenging to identify effective dopants in some specific systems. Herein, we discovered that Y doping significantly reduced the carrier concentration, enhanced the power factor, and, therefore, boosted thermoelectric performance. The high Y-doping efficiency had origin in the fact that the compensating effect due to Ge vacancies was weaker in comparison to other dopants in GeTe because the slightly increased rhombohedral interaxial angle suggested that the Ge-vacancy concentration would not be altered dramatically. In addition, first-principles calculations revealed that Y doping did not induce significant modifications on the band structure, consistent with electrical transport measurement results. Moreover, Bi doping was found to be more powerful than Sb doping to further increase electrical resistivity and to enhance performance in which the highest peak ZT ∼ 1.8 together with a high average ZT ∼ 1.1 from 300 K to 723 K was achieved. Our work not only highlighted the efficacy of Y doping in enhancing the thermoelectric performance of the GeTe system but also developed advanced GeTe-based materials for power generation applications.
Possibility of using tetrafluorohydrazine as an oxidiser in a supersonic cw chemical HF laser
Authors: Fedorov I.A.
Published: January 2021

We report a computational and experimental study of the possibility of replacing NF3 nitrogen trifluoride, which is used in the NF3 – D2 – He fuel composition in the atomic fluorine generator of a supersonic cw chemical HF laser, with N2F4 tetrafluorohydrazine. As a result of comparing the specific energy characteristics of an HF laser operating with each of the oxidisers, it is shown that the replacement of nitrogen trifluoride with tetrafluorohydrazine in the same laser model leads to an increase in the specific energy output by 13% – 15%. In this case, it is possible to reduce the specific mass of the oxidiser storage system (the ratio of the mass of the oxidiser storage system to the laser facility power), reduce the oxidiser tank dimensions, and simplify the active medium generator design by eliminating the ignition system of the NF3 oxidiser with a D2 primary fuel.
Analytical model of fluorescence intensity for the estimation of fluorophore localisation in biotissue with dual-wavelength fluorescence imaging
Authors: Khilov A.V. , Sergeeva E.A. , Kurakina D.A. , Turchin I.V. , Kirillin M.Yu.
Published: January 2021

Analytical expression for the fluorescence response of a photosensitiser uniformly distributed in the superficial layer of biotissue is obtained in the diffusion approximation of radiative transfer theory, and the approach for estimating the fluorescent layer thickness based on dual-wavelength excitation of fluorescence is proposed. It is shown that the error in estimation of the fluorescent layer thickness employing the ratio of the fluorescence signals obtained at different excitation wavelengths does not exceed 30 % for the thickness range of 0.1 – 2 mm in the case of 30 %-variation of biotissue optical properties.
Polyacrylamide-based phantoms of human skin for hyperspectral fluorescence imaging and spectroscopy
Authors: Shupletsov V.V. , Zherebtsov E.A. , Dremin V.V. , Popov A.P. , Bykov A.V. , Potapova E.V. , Dunaev A.V. , Meglinski I.V.
Published: January 2021

Based on the combined use of polymerisable polyacrylamide, collagen and an aqueous solution of Flavin adenine dinucleotide (FAD), we have developed a new technique for fabrication of composite phantoms mimicking fluorescence properties of human skin. A comparative analysis of the absorption and scattering coefficients, refractive indices, as well as fluorescence spectra of phantoms with different concentrations of FAD measured with the combined use of a CCD spectrometer and a hyperspectral camera is presented. To obtain values of scattering coefficients close to those for human skin, zinc oxide (ZnO) nanoparticles are added to the polyacrylamide polymer structure. Variations both in the shape of the spectrum and in the intensity of the fluorescence signal in the phantoms are provided by the changes in the volume fraction of FAD and collagen. It is shown that the model fluorescence spectra are in good agreement with the results of direct human skin measurementsin vivo.
Can Google Trends data confirm the need for charismatic species to generate interest in conservation?
Authors: Zieger Michael , Springer Steffen
Published: January 2021

In nature conservation and environmental protection, there is the thesis that charismatic flagship species generate a high level of public interest that can be used for nature conservation efforts. Among other things, Google Trends has already been introduced to analyse nature conservation issues. In this study, interest in selected charismatic species were compared with the terms ‘nature reserve’, ‘conservation’, ‘environmental protection’, and ‘endangered species’ from the field of nature and environmental protection in three selected English-speaking countries and worldwide by using Google Trends. Although some individual, selected terms, e.g. ‘panda’ or ‘thylacine’, could be valuable ambassadors for nature and environmental protection in certain regions, a more general benefit or need for charismatic species to generate interest in conservation and environmental issues was not clearly demonstrated in this study.
Runx1 and Runx3 drive progenitor to T-lineage transcriptome conversion in mouse T cell commitment via dynamic genomic site switching
Authors: Shin Boyoung , Hosokawa Hiroyuki , Romero-Wolf Maile , Zhou Wen , Masuhara Kaori , Tobin Victoria R. , Levanon Ditsa , Groner Yoram , Rothenberg Ellen V.
Published: January 2021

Significance

T-lineage specification requires waves of gene network changes to terminate multipotency and establish T identity. Circumstantial evidence has suggested roles for Runt domain-related (Runx) factors in these regulatory events; Runx1 is strongly expressed, but Runx1 knockouts have previously shown little impact during stages around T-lineage commitment. We show that Runx1 and Runx3 function together to drive T-lineage commitment, binding the same sites. Double knockouts block both activation of T-lineage genes and repression of progenitor genes. Contrasting with the stable activity of Runx proteins throughout these stages, Runx factors preferentially regulate target genes that sharply change expression during T commitment. We show that this reflects pronounced, global redistributions of Runx binding choices across the genome before and after T-lineage commitment.
Portrayal of power in manifestos
Authors: Farrukh Fizza , Masroor Farzana
Published: January 2021

Power, conforming to particular political groups of the society, is exercised on the masses by making them believe
in the legitimacy of that dominance. This association enables the groups to exercise their power and promulgate their ideologies
through their discourse as well. One illustration of this discourse appears in the form of political manifestos. Utilizing the
tool of language, the political actors (as agents of political parties) set agendas, pertinent topics and position their stance in
these manifestos. Framed under critical discourse analysis, the current study attempts to investigate this act of ‘legitimation’
promulgated by Chilton (2004) and the strategies of Authority Legitimation, devised by
Van Leeuwen (2008). The article illustrates how the power-holders utilize their
linguistic resources to authorize their stance, idea, and action. The study helps explicating the relation between power, ideology
and language and promulgates consciousness regarding the reality constructed by humans, as social and political actors.
The versatility of liver X receptors in T cell homeostasis: Location, location, location!
Authors: Phan Truong San , Brunner Thomas
Published: January 2021

Nuclear receptors control the transcriptional program of target cells and thereby their phenotype and activities. Two complementary studies by Micheals et al. (https://doi.org/10.1084/jem.20201311) and Chan et al. (https://doi.org/10.1084/jem.20200318) published in JEM uncover the cell type–specific expression and role of the nuclear receptors liver X receptors in the regulation of T cell homeostasis and function.
A dual-frequency piezoelectric micromachined ultrasound transducer array with low inter-element coupling effects
Authors: Liu Lifang , Ji Weiliang , Xing Zhanqiang , Sun Xiangyu , Chen Yu , Du Yijia , Qin Feng
Published: January 2021

This paper presents a dual-frequency piezoelectric micromachined ultrasonic transducer (PMUT) line array with low crosstalk level, which was fabricated on silicon-on-insulator (SOI) wafers with sputtered piezoelectric thin film (PZT) and Si diaphragm structure. The obtained array consists of 120 of 0.77 MHz and 192 of 2.30 MHz PMUT units in total with minimum interspace of 50 μm. Due to the high piezoelectric coefficient of PZT, the PMUT shows high transmitting sensitivity in air and good effective electromechanical coupling factor. The displacement sensitivities are assessed to be 595 nm V−1 and 112 nm V−1 at the resonant frequencies of 0.77 MHz and 2.30 MHz respectively in air. To reduce the vibration coupling, rectangular grooves in the bottom silicon are designed between the adjacent line elements, and the PMUT units in the array are arranged in a mis-aligned style. Modal analysis for the 0.77 MHz units indicates neighbouring coupling-vibration decreases greatly from 44.5% to 14.8% of the excited vibration when the excited line is driven at 4Vpp, which proves both the grooves and the mis-aligned ranking are effective for coupling effect reduction. Moreover, results indicate the coupling effect between different frequencies can be ignored due to their inherent resonance characteristics. The sound pressures for a single 0.77 MHz line element and 2.30 MHz line element are evaluated to be 53 kPa and 73 kPa at a distance of 1 cm in water. This high performance dual-frequency PMUT line array makes some high resolution imaging methods possible based on PMUT technology, such as those of dual-frequency, total focus.
Limitations on MEMS design resulting from random stress gradient variations in sputtered thin films
Authors: Zhu William Z , Assylbekova Meruyert , McGruer Nicol E
Published: January 2021

Residual stress gradients often negatively affect the performance of MEMS devices, causing film curvature and changing the designed gaps of released structures. In this work, we built folded beams designed to compensate for the film curvature and keep the actuator gaps of sensitive resonant switches constant. While the average stress gradient is cancelled by our designs, we find that random variations in the stress gradient (rather than random variations in device dimensions) cause the majority of the observed variation in actuator gap. To our knowledge, this has not previously been reported, and represents an important limitation on MEMS designs using sputtered films. The standard deviation of the 400 nm contact gap for a folded beam of total length 152 µm and width 108 µm was measured to be about 134 nm. Using parameters measured from test cantilevers, our simulations predict that about 98% of the variation in contact gap is due to stress gradient variation, rather than variations in device geometry.
Entanglement of quantum oscillators coupled to different heat baths
Authors: Syu Wei-Can , Lee Da-Shin , Yeh Chen-Pin
Published: January 2021

We study the non-equilibrium dynamics of two coupled oscillators interacting with their own heat baths of quantum scalar fields at different temperature T
1 and T
2 with bilinear couplings between them. We particularly focus on the entanglement or inseparability property of their quantum states. The critical temperatures of two respective oscillators, T
1c and T
2c, higher than which the entanglement disappears, can be determined. It is found that when two damping parameters are largely different, say γ
1 ≪ γ
2, the critical temperature T
1c with respect to the frequency Ω+, the higher frequency among two normal modes frequencies, can be very large, T
1c ≫ Ω+, while T
2c ∝ Ω+ with the possibility of hot entanglement. The entanglement of two oscillators with the temperature-dependent damping parameters γ
1;2,T
from heat baths is also discussed.
Tunable Poisson’s ratio and tension-compression asymmetry of graphene-copper nanolayered composites
Authors: Zhang Sen , Zhang Qiang , Liu Xiaoyi , Luo S N
Published: January 2021

The Poisson’s ratios of graphene-copper nanolayered (GrCuNL) composites under tension and compression are investigated by molecular dynamics and theoretical analysis. The Poisson’s ratio of a GrCuNL composite can be tuned by tailoring its repeat layer spacing without changing the topological structures. The effect of constituent nanocrystalline Cu grain size on the Poisson’s ratio is negligible. There are remarkable in-plane anisotropy and tension-compression asymmetry in the Poisson’s ratio due to the chiral difference in compressive stress in graphene layers. A mechanical model considering the chirality and repeat layer spacing is proposed, which can accurately predict the Poisson’s ratio of a GrCuNL composite. For stable GrCuNL composites, the repeat layer spacing should be larger than 2 nm, and their tunable range of Poisson’s ratio is 0.1–0.35.
A study of open shell nuclei using chiral two-body interactions
Authors: Puddu G
Published: January 2021

We apply the hybrid-multi-determinant method using the recent chiral two-body interactions of Entem–Machleidt–Nosyk without renormalization to few nuclei up to A = 48. Mostly we use the bare fifth order NN interaction N4LO-450. For 24Mg and 48Cr the excitation energies of the

2

1

+

states are far larger than the corresponding experimental values.
Optical fiber SPR magnetic field sensor based on photonic crystal fiber with the magnetic fluid as cladding
Authors: Zhu Liangquan , Zhao Na , Lin Qijing , Zhao Libo , Jiang Zhuangde
Published: January 2021

In this paper, a novel optical fiber surface plasmon resonance (SPR) magnetic field sensor is proposed and experimentally demonstrated. The structure is fabricated by splicing a section of photonic crystal fiber between two multimode fibers. After the structure is coated with 10 nm Cr and 50 nm Au, the high refractive index (RI) sensitivity, from 1973.72 nm RIU−1 to 3223.32 nm RIU−1 in the range of 1.3326–1.3680, verifies the SPR sensor, which is higher than the structure based on single mode fiber with the same coating. In addition, the microscopic mechanism of the tunable characteristics of magnetic fluid RI with the ambient magnetic field is simulated by the molecular dynamics method. To measure the external magnetic field, the sensing region of the SPR sensor is fully inserted in a capillary tube, which is filled with magnetic fluid and sealed with UV glue. A maximum sensitivity of 4.42 nm mT−1 is achieved in the range of 0–24 mT, experimentally. Due to high sensitivity, simple manufacturing and compact size, the proposed sensor possesses attractive application prospects in environmental monitoring, power transmission and biomedical applications.
Towards field-effect controlled graphene-enhanced Raman spectroscopy of cobalt octaethylporphyrin molecules
Authors: Sleziona Stephan , Rauls Simon , Heckhoff Tobias , Christen Leonard , Pollmann Erik , Madauß Lukas , Franzka Steffen , Lorke Axel , Wende Heiko , Schleberger Marika
Published: January 2021

During the last decade graphene-enhanced Raman spectroscopy has proven to be a powerful tool to detect and analyze minute amounts of molecules adsorbed on graphene. By using a graphene-based field-effect device the unique opportunity arises to gain a deeper insight into the coupling of molecules and graphene as graphene’s Fermi level can be controlled by the transistor`s gate voltage. However, the fabrication of such a device comes with great challenges because of contaminations stemming from processing the device inevitably prevent direct adsorption of the molecules onto graphene rendering it unsuitable for field-effect controlled graphene-enhanced Raman spectroscopy measurements/experiments. In this work, we solve this problem by establishing two different fabrication procedures for such devices, both of which are in addition compatible with large area and scalable production requirements. As a first solution, selective argon cluster irradiation is shown to be an efficient way to remove resist residues after processing. We provide evidence that after the irradiation the enhancement of the molecular Raman signal can indeed be measured, demonstrating that this procedure cleans graphene’s surface sufficiently enough for direct molecular adsorption. As a second solution, we have developed a novel stacking method to encapsulate the molecules in between two graphene layers to protect the underlying graphene and molecular layer from the harsh conditions during the photolithography process. This method combines the advantages of dry stacking, which leads to a perfectly clean interface, and wet stacking processes, which can easily be scaled up for large area processing. Both approaches yield working graphene transistors with strong molecular Raman signals stemming from cobalt octaehtylporphyrin, a promising and prototypical candidate for spintronic applications, and are therefore suitable for graphene based molecular sensing applications.
Electrostatic tip effects in scanning probe microscopy of nanostructures
Authors: Casper Clayton B , Ritchie Earl T , Teitsworth Taylor S , Kabos Pavel , Cahoon James F , Berweger Samuel , Atkin Joanna M
Published: January 2021

Electrical scanning probe microscopies (SPM) use ultrasharp metallic tips to obtain nanometer spatial resolution and are a key tool for characterizing nanoscale semiconducting materials and systems. However, these tips are not passive probes; their high work functions can induce local band bending whose effects depend sensitively on the local geometry and material properties and thus are inherently difficult to quantify. We use sequential finite element simulations to first explore the magnitude and spatial distribution of charge reorganization due to tip-induced band bending (TIBB) for planar and nanostructured geometries. We demonstrate that tip-induced depletion and accumulation of carriers can be significantly modified in confined geometries such as nanowires compared to a bulk planar response. This charge reorganization is due to finite size effects that arise as the nanostructure size approaches the Debye length, with significant implications for a range of SPM techniques. We then use the reorganized charge distribution from our model to describe experimentally measured quantities, using in operando scanning microwave impedance microscopy measurements on axial p-i-n silicon nanowire devices as a specific example. By incorporating TIBB, we reveal that our experimentally observed enhancement (absence) of contrast at the p-i (i-n) junction is explained by the tip-induced accumulation (depletion) of carriers at the interface. Our results demonstrate that the inclusion of TIBB is critical for an accurate interpretation of electrical SPM measurements, and is especially important for weakly screening or low-doped materials, as well as the complex doping patterns and confined geometries commonly encountered in nanoscale systems.
Field-programable-gate-array-based distributed coincidence processor for high count-rate online positron emission tomography coincidence data acquisition
Authors: Cheng Xinyi , Hu Kun , Yang Dongxu , Shao Yiping
Published: January 2021

For positron emission tomography (PET) online data acquisition, a centralized coincidence processor (CCP) with single-thread data processing has been used to select coincidence events for many PET scanners. A CCP has the advantages of highly integrated circuit, compact connection between detector front-end and system electronics and centralized control of data process and decision making. However, it also has the drawbacks of data process delay, difficulty in handling very high count-rates of single and coincidence events and complicated algorithms to implement. These problems are exacerbated when implementing a CCP on a field-programable-gate-array (FPGA) due to increased routing congestion and reduced data throughput. Industry companies have applied non-centralized or distributed data processing to solve these problems, but those solutions remain either proprietary or lack full disclosure of technical details that make the techniques unclear and difficult to adapt for most research communities. In this study, we investigated the use of a set of distributed coincidence processors (DCP) that can address the CCP problems and be implemented relatively easily. Each coincidence processor exclusively connects one detector pair and selects coincidence events from this detector pair only, which breaks a centralized coincidence process to a collection of independent and parallel processes. DCP can significantly minimize the data process delay, maximize count-rates of coincidence events and simplify implementation by implementing a single coincidence processor with one detector pair and replicating it to the rest. A prototype DCP with 42 coincidence processors was implemented on an off-the-shelf FPGA development board for a small PET with 12 detectors configured with 42 detector pairs. DCP performances were tested with both pulsed signals and gamma ray interactions. There was no coincidence data loss up to the detector’s maximum singles count-rate (250 k s−1). Approximately 1.2 k registers were utilized for each coincidence processor and the FPGA resource utilization was proportional to the number of coincidence processors. Coincidence timing spectra showed the results from accurately acquired coincidence events. In conclusion: complementary to CCP, DCP can provide high count-rate capability, with a simplified algorithm for implementation and potentially a practical solution for online acquisition of a PET with a larger number of detector pairs or for ultrahigh-throughput imaging.
Long-length tomosynthesis and 3D-2D registration for intraoperative assessment of spine instrumentation
Authors: Zhang Xiaoxuan , Uneri Ali , Wu Pengwei , Ketcha Michael D , Jones Craig K , Huang Yixuan , Lo Sheng-Fu Larry , Helm Patrick A , Siewerdsen Jeffrey H
Published: January 2021

Purpose. A system for long-length intraoperative imaging is reported based on longitudinal motion of an O-arm gantry featuring a multi-slot collimator. We assess the utility of long-length tomosynthesis and the geometric accuracy of 3D image registration for surgical guidance and evaluation of long spinal constructs. Methods. A multi-slot collimator with tilted apertures was integrated into an O-arm system for long-length imaging. The multi-slot projective geometry leads to slight view disparity in both long-length projection images (referred to as ‘line scans’) and tomosynthesis ‘slot reconstructions’ produced using a weighted-backprojection method. The radiation dose for long-length imaging was measured, and the utility of long-length, intraoperative tomosynthesis was evaluated in phantom and cadaver studies. Leveraging the depth resolution provided by parallax views, an algorithm for 3D-2D registration of the patient and surgical devices was adapted for registration with line scans and slot reconstructions. Registration performance using single-plane or dual-plane long-length images was evaluated and compared to registration accuracy achieved using standard dual-plane radiographs. Results. Longitudinal coverage of ∼50–64 cm was achieved with a single long-length slot scan, providing a field-of-view (FOV) up to (40 × 64) cm2, depending on patient positioning. The dose-area product (reference point air kerma × x-ray field area) for a slot scan ranged from ∼702–1757 mGy·cm2, equivalent to ∼2.5 s of fluoroscopy and comparable to other long-length imaging systems. Long-length scanning produced high-resolution tomosynthesis reconstructions, covering ∼12–16 vertebral levels. 3D image registration using dual-plane slot reconstructions achieved median target registration error (TRE) of 1.2 mm and 0.6° in cadaver studies, outperforming registration to dual-plane line scans (TRE = 2.8 mm and 2.2°) and radiographs (TRE = 2.5 mm and 1.1°). 3D registration using single-plane slot reconstructions leveraged the ∼7–14° angular separation between slots to achieve median TRE ∼2 mm and <2° from a single scan. Conclusion. The multi-slot configuration provided intraoperative visualization of long spine segments, facilitating target localization, assessment of global spinal alignment, and evaluation of long surgical constructs. 3D-2D registration to long-length tomosynthesis reconstructions yielded a promising means of guidance and verification with accuracy exceeding that of 3D-2D registration to conventional radiographs.
Accelerated 3D image reconstruction with a morphological pyramid and noise-power convergence criterion
Authors: Sisniega A , Stayman J W , Capostagno S , Weiss C R , Ehtiati T , Siewerdsen J H
Published: January 2021

Model-based iterative reconstruction (MBIR) for cone-beam CT (CBCT) offers better noise-resolution tradeoff and image quality than analytical methods for acquisition protocols with low x-ray dose or limited data, but with increased computational burden that poses a drawback to routine application in clinical scenarios. This work develops a comprehensive framework for acceleration of MBIR in the form of penalized weighted least squares optimized with ordered subsets separable quadratic surrogates. The optimization was scheduled on a set of stages forming a morphological pyramid varying in voxel size. Transition between stages was controlled with a convergence criterion based on the deviation between the mid-band noise power spectrum (NPS) measured on a homogeneous region of the evolving reconstruction and that expected for the converged image, computed with an analytical model that used projection data and the reconstruction parameters. A stochastic backprojector was developed by introducing a random perturbation to the sampling position of each voxel for each ray in the reconstruction within a voxel-based backprojector, breaking the deterministic pattern of sampling artifacts when combined with an unmatched Siddon forward projector. This fast, forward and backprojector pair were included into a multi-resolution reconstruction strategy to provide support for objects partially outside of the field of view. Acceleration from ordered subsets was combined with momentum accumulation stabilized with an adaptive technique that automatically resets the accumulated momentum when it diverges noticeably from the current iteration update. The framework was evaluated with CBCT data of a realistic abdomen phantom acquired on an imaging x-ray bench and with clinical CBCT data from an angiography robotic C-arm (Artis Zeego, Siemens Healthineers, Forchheim, Germany) acquired during a liver embolization procedure. Image fidelity was assessed with the structural similarity index (SSIM) computed with a converged reconstruction. The accelerated framework provided accurate reconstructions in 60 s (SSIM = 0.97) and as little as 27 s (SSIM = 0.94) for soft-tissue evaluation. The use of simple forward and backprojectors resulted in 9.3× acceleration. Accumulation of momentum provided extra ∼3.5× acceleration with stable convergence for 6–30 subsets. The NPS-driven morphological pyramid resulted in initial faster convergence, achieving similar SSIM with 1.5× lower runtime than the single-stage optimization. Acceleration of MBIR to provide reconstruction time compatible with clinical applications is feasible via architectures that integrate algorithmic acceleration with approaches to provide stable convergence, and optimization schedules that maximize convergence speed.
Application of lung substitute material as ripple filter for multi-ion therapy with helium-, carbon-, oxygen-, and neon-ion beams
Authors: Inaniwa Taku , Abe Yasushi , Suzuki Masao , Lee Sung Hyun , Mizushima Kota , Nakaji Taku , Sakata Dousatsu , Sato Shinji , Iwata Yoshiyuki , Kanematsu Nobuyuki , Shirai Toshiyuki
Published: January 2021

A development project for hypo-fractionated multi-ion therapy has been initiated at the National Institute of Radiological Sciences in Japan. In the treatment, helium, carbon, oxygen, and neon ions will be used as primary beams with pencil beam scanning. A ripple filter (RiFi), consisting of a thin plastic or aluminum plate with a fine periodic ridge and groove structure, has been used to broaden the Bragg peak of heavy-ion beams in the beam direction. To sufficiently broaden the Bragg peak of helium-, carbon-, oxygen-, and neon-ion beams with suppressed lateral scattering and surface dose inhomogeneity, in this study, we tested a plate made of a lung substitute material, Gammex LN300, as the RiFi. The planar integrated dose distribution of a 183.5 MeV u−1 neon-ion beam was measured behind a 3 cm thick LN300 plate in water. The Bragg peak of the pristine beam was broadened following the normal distribution with the standard deviation σ value of 1.29 mm, while the range of the beam was reduced by 8.8 mm by the plate. To verify the LN300 performance as the RiFi in multi-ion therapy, we measured the pencil beam data of helium-, carbon-, oxygen- and neon-ion beams penetrating the 3 cm thick LN300 plate. The data were then modeled and used in a treatment planning system to achieve a uniform 10% survival of human undifferentiated carcinoma cells within a cuboid target by the beam for each of the different ion species. The measured survival fractions were reasonably reproduced by the planned ones for all the ion species. No surface dose inhomogeneity was observed for any ion species even when the plate was placed close to the phantom surface. The plate made of lung substitute material, Gammex LN300, is applicable as the RiFi in multi-ion therapy with helium-, carbon-, oxygen- and neon-ion beams.
Electrical modeling of cylindrical dielectric elastomer transducers
Authors: van Kessel R , Bauer P , Ferreira J A
Published: January 2021

Dielectric elastomer transducers (DETs) are commonly modeled by lumped-element models (LEMs), however such models do not capture the cutoff behavior that manifests at relatively low frequencies due to the high resistivity of the stretchable electrodes. Moreover, the contribution of the electrodes into the lumped series resistance is not accurately known. The aim of this work is to define the accuracy and frequency limits of the LEM and to derive the exact values of its lumped components. This is achieved by developing a detailed three-dimensional distributed-element model (DEM) of the transducer structure. Based thereon, analytical expressions are developed for the LEM components and limits are explored. Through numerical evaluation of the DEM it is found that only two-third of the single-polarity electrode resistance contributes to the lumped series resistance, which is three times lower than predicted by existing models. Comparison between the LEM and DEM further shows that the LEM is adequate for frequencies significantly below the cutoff frequency. Thereafter, capacitance and resistance fall off as a result of signal propagation limitations. This has been experimentally verified. The developed DEM and established validity range of the simple LEM allows for more accurate sensors and better optimized transducers designs, with up to three times less electrode material.
Predictive vision of development paths of pump technical systems
Authors: Kovaliov I A , Ratushnyi A V , Dzafarov T V , Mandryka A S , Ignatiev A S
Published: January 2021

In the work on the basis of objective laws on the development of technical systems and the features of the VI technological order directions of further development of pump technical systems are analyzed. The reserves of systems that already exist without changing the principle of the working process are shown, the concept of "combined working process" is introduced and the question of the necessity and possibility of searching for fundamentally different physical processes of liquid power transfer, including at the micro level, is raised.
The influence of the design parameters of the rotors of the planetary hydraulic motor on the change in the output characteristics of the mechatronic system
Authors: Panchenko A , Voloshina A , Titova O , Panchenko I
Published: January 2021

One of the main stages of research related to increasing the efficiency of planetary hydraulic motors operating as part of the mechatronic systems of self-propelled vehicles is the experimental research of real samples. Experimental studies of the influence of design features of the rotor system of serial and modernized hydraulic motors on the output characteristics of mechatronic systems were carried out by means of comparative bench tests. A technique has been developed for conducting comparative bench studies of planetary hydraulic motors. A test bench scheme is proposed for testing a family of unified series of high-torque, low-speed planetary-type hydraulic motors. The main factors determining the change in the output characteristics of the planetary hydraulic motor, taking into account the design features of the rotor system, are: pressure drop, flow rate of the working fluid and the error the manufacturing form of the gear profile of its rotors. Tests of planetary hydraulic motors with a serial and modernized rotor systems were carried out. The modernization of the rotor system was carried out by changing the design of the external and internal rotors in order to reduce the shape error of their gear profile. As a result of experimental studies, it was found that eliminating the error the manufacturing form of the rotors of the modernized hydraulic motor can significantly improve its output characteristics - increase the torque at specified rotation speeds, and as a result, increase the hydromechanical and overall efficiency of the mechatronic system as a whole.
A numerical solution of temperature distribution in the clearance and the sealing rings of the non-contact face seal
Authors: Dindorf R , Wos P
Published: January 2021

The study presents a numerical analysis of the temperature distribution in the clearance and the temperature distribution in the rings of a non-contact face seal. Non-contact face seals designed for turbine pumps to meet the requirements of lower leakage, longer life, and more frequent starting and stopping are included in this test. A thermo-hydro-mechanical model of the non-contact face seal clearance has been presented. Based on this model, dimensionless differential equations were derived to determine the temperature distribution in the clearance seal gap and the temperature distribution in sealing rings. The numerical solution of differential equations allowed the presentation of temperature characteristics for different parameters of the analyzed non-contact face seal. The analysis took into account hydrodynamic and thermodynamic phenomena in the clearance of the face seal depending on pressure, leakage flow rate and temperature of the sealing fluid, clearance dimensions, thermal parameters of the sealing rings, and operation parameters of the rotating machine. The temperature distribution in a non-contact face seal can also be used to determine the thermal deformation of the sealing rings. The presented numerical model is useful in the design of non-contact face seals because it allows the selection of parameters stabilizing the thermo-hydro-mechanical state of the two mating sealing rings.
Determination of angular stiffness coefficient of the annular seal by experiment-calculation
Authors: Gorovoy S , Golovchenko G , Dumanchuk M
Published: January 2021

Hydrodynamic forces in annular seals of centrifugal pumps create a significant effect on the vibrational activity of the rotor as a whole. Theoretical and experimental studies of various authors made it possible to establish the structure of hydrodynamic forces and determine the magnitude of the coefficients of radial forces. The authors of this work obtained quantitative load characteristics of the rotor in an annular seal at specially created laboratory experimental stands at various pressure drops and significant angles of misalignment of the rotor axis relative to the seal axis. Static experiments were also conducted with annular seals of various lengths with a constant differential pressure of the liquid and a fixed angle of misalignment of the rotor axis relative to the axis of the annular seal. The given misalignment angle was obtained as a result of the action of various external forces on the rotor. In addition to static experiments, dynamic rotor tests were carried out. Experimentally obtained amplitude - frequency characteristics of the forced radial - angular oscillations of the rotor, which is dynamically mounted in two symmetrical annular seals. From the experimental characteristics, the critical frequency of the rotor angular oscillations in the seals was determined. According to theoretical formulas, taking into account the value of the coefficient of angular stiffness of the annular seal, the frequency of the natural angular oscillations of the rotor in the annular seals was calculated. A comparison of theoretical and experimental values indicates their good quantitative agreement.
Magnetic field in the core of a magnetic fluid seal taking magnetic structural elements into account
Authors: Radionov A V , Podoltsev A D , Radionova A A
Published: January 2021

According to the results of the finite element analysis of the magnetic field of the liquid metal seal designed to protect the bearing assembly from external aggressive influences, it is shown that its mounting directly on the bearing shield having magnetic properties leads to an increase in magnetic fluxes of scattering and to a decrease in the peak value of magnetic induction in the working the gap from 1, 6 T to 1,1 T., i.e. to a decrease of 31%. The use of a non-magnetic insert between the seal and the bearing assembly allows this induction to be increased. The dependence of this induction on the thickness of the insert is given, which makes it possible to choose its rational value when installing the seal. It is shown that the use of an additional permanent magnet located in the area of this insert allows one to increase the peak value of magnetic induction in the working gap from 1.3 T to 1.75 T and, as a result, improve the performance of the seal.
New technology for restoring Babbitt coatings
Authors: Konoplianchenko Ie , Tarelnyk V , Martsynkovskyy Vas , Gaponova O , Lazarenko A , Sarzhanov A , Mikulina M , Zhengchuan Zh , Pirogov V
Published: January 2021

The reasons for reducing the durability of sliding bearings and the factors formed both at the stage of their manufacture and during operation are considered. Taking into account the types of destruction of sliding bearing coatings (exfoliation, disintegration of individual sections, field failure) the need for developing technological recommendations for their repair is demonstrated. The analysis of existing technological methods for restoring worn surfaces of parts is shown. The technique for applying the method of electrospark alloying to repair bearing liners is represented. The technologies of applying combined electrospark coatings to increase the adhesion strength of the substrate to the antifriction Babbit layer are described. There have been revealed the correlation dependences of the quality characteristics of the Babbit coatings restored by the method of electrospark alloying versus the technological parameters of the process. This makes it possible to significantly implement the methodology for controlling the surface layer quality while manufacturing and repairing the products with Babbit coatings. A technique has been developed for determining the mass transfer equation constants and for predicting the roughness. The mathematical models have been proposed to specify the quality parameters of the layers being formed in the course of the Babbit coating restoration based on the energy parameters of the electrospark alloying plant.