bluuebunny/crossref_metadata_2025 huggingface dataset:
Surgical Skills Olympiad: A 4-Year Experience in a General Surgery Residency Program
Authors: Oberoi Kurun P. S. , Caine Akia D. , Schwartzman Jacob , Livingston David H. , Merchant Aziz M. , Kunac Anastasia
Published: August 2021

Background The acquisition of operative skills is the critical defining component of general surgery training. Performing simulated tasks has been shown to increase a resident's technical skills. As such, we devised the Surgical Skills Olympiad, an annual simulation-based skills competition. We examined our 4-year experience with the Olympiad at a large academic general surgery residency program.

Objective This study aimed to use competition to motivate trainees to increase the time they spent practicing basic surgical skills, resulting in improved performance over time.

Methods Teams were formed from members of each postgraduate year (PGY) class. Competition tasks were level specific: knot tying for PGY-1, basic laparoscopy for PGY-2, handsewn bowel anastomosis for PGY-3, vascular anastomosis for PGY-4, and advanced laparoscopy for PGY-5. Task scores over a 4-year period (2014–2017) were analyzed and a survey of participating teaching faculty was conducted.

Results Ten faculty members responded to the survey, for a response rate of 63%. A total of 50% respondents felt that the caliber of surgical skills increased since the Olympiad was implemented. Ninety percent agreed that the Olympiad was beneficial for residents to assess their skills against their peers. Over 4 years, there was an improvement in scores for suturing task, advanced laparoscopy, and bowel anastomosis (p < 0.05 for all three).

Conclusion A residency-wide surgical skills competition can improve resident performance in technical tasks and promote faculty engagement in resident skills training.
1.1.1 General Principles of Metal/Metal Dual Catalysis
Authors: Nakao Y.
Published: August 2021

The background and principles of dual metal/metal catalysis are briefly introduced in this section, with a particular focus on novel C–C bond-forming cross-coupling-type reactions. By taking advantage of synergistic dual metal/metal catalysis, these transformations have provided the synthetic and organometallic communities with new ideas to design challenging transformations that are difficult to catalyze using a conventional, single metal catalyst.
Combination of electric and acoustic actuation removes bubbles from liquid without buoyancy
Authors: Liebendorfer Adam
Published: August 2021

Tuning acoustic signals to frequency of bubbles produces microstreams and oscillatory motion for potential use in medical microrobotics and heat exchangers.
Predictive optical photoabsorption of Ag24Au(DMBT)18− via efficient TDDFT simulations
Authors: Medves Marco , Sementa Luca , Toffoli Daniele , Fronzoni Giovanna , Krishnadas Kumaranchira Ramankutty , Bürgi Thomas , Bonacchi Sara , Dainese Tiziano , Maran Flavio , Fortunelli Alessandro , Stener Mauro
Published: August 2021

We report a computational study via time-dependent density-functional theory (TDDFT) methods of the photo-absorption spectrum of an atomically precise monolayer-protected cluster (MPC), the Ag24Au(DMBT)18 single negative anion, where DMBT is the 2,4-dimethylbenzenethiolate ligand. The use of efficient simulation algorithms, i.e., the complex polarizability polTDDFT approach and the hybrid-diagonal approximation, allows us to employ a variety of exchange-correlation (xc-) functionals at an affordable computational cost. We are thus able to show, first, how the optical response of this prototypical compound, especially but not exclusively in the absorption threshold (low-energy) region, is sensitive to (1) the choice of the xc-functionals employed in the Kohn–Sham equations and the TDDFT kernel and (2) the choice of the MPC geometry. By comparing simulated spectra with precise experimental photoabsorption data obtained from room temperature down to low temperatures, we then demonstrate how a hybrid xc-functional in both the Kohn–Sham equations and the diagonal TDDFT kernel at the crystallographically determined experimental geometry is able to provide a consistent agreement between simulated and measured spectra across the entire optical region. Single-particle decomposition analysis tools finally allow us to understand the physical reason for the failure of non-hybrid approaches.
Faraday cup sizing for electric propulsion ion beam study: Case of a field-emission-electric propulsion thruster
Authors: Hugonnaud V. , Mazouffre S. , Krejci D.
Published: August 2021

This article provides information about the sizing and standardization of a Faraday cup (FC) used as a plasma diagnostic. This instrument is used to accurately map the ion beam profile produced by an electric propulsion (EP) device. A FC is a cylindrical probe that uses an electrode, termed collector, to measure the current. Several studies have shown the relevance of adding an extra electrode, called collimator, to define the collection area and to minimize interactions with the ambient plasma. Both the electrodes are encapsulated into an isolated metallic housing that prevents ambient plasma from disturbing the measurements. In this case study, a field-emission-electric propulsion (FEEP) thruster is used. The FEEP technology uses electrostatic fields to extract liquid metal (indium) ions from a sharp surface and accelerates them to high velocities, providing thrust. The FEEP model used in this study is the ENPULSION NANO thruster from the Austrian company Enpulsion. We present results focusing on the sizing of a FC in terms of cup length, aperture diameter, and collection solid angle as well as on the material exposure to the ion beam. For a far-field ion beam study of a FEEP indium based electric thruster, our study outcomes show that a FC optimum sizing is a 50 mm long collector cup and a 7 mm wide inlet aperture. Moreover, shielding the repeller/collimator from direct exposure to the ion beam seems to greatly minimize perturbation during ion current acquisition. Finally, to only measure the ion current, a negative potential should be applied to the collector and repeller, where the latter is more negative. This study contributes to the effort on diagnostic standardization for EP device characterization. The goal is to enable repetitive and reliable determination of thruster parameters and performances.
Direct evidence of the stacking fault-mediated strain hardening phenomenon
Authors: Frank M. , Nene S. S. , Chen Y. , Thapliyal S. , Shukla S. , Liu K. , Sinha S. , Wang T. , Frost M. J. , An K. , Mishra R. S.
Published: August 2021

Strain hardening in metallic materials delays catastrophic failure at stresses beyond the yield strength by the formation of obstacles to dislocation motion during plastic deformation. Conventional measurement of the instantaneous strain hardening rate originates from load–displacement data acquired during uniaxial mechanical testing, rather than the evolution of obstacles. In order to resolve hardening from the perspective of the very obstacles that cause strengthening, we used an in situ neutron diffraction experimental approach to determine the strain hardening rate based upon real-time measurement of stacking fault interspacing during plastic deformation. Results provide clear evidence of the evolving contribution of obstacles during plastic deformation. The collapse of interspacing between multiple obstacle types enabled immense strain hardening in a Fe38.5Mn20Cr15Co20Si5Cu1.5 high entropy alloy leading to a true tensile strength of ∼1.7 GPa along with elongation of ∼35% at room temperature.
HIV, syphilis and hepatitis B prevalence, related risk behaviours and correlates of condom use among transgender women in two cities in Sri Lanka: findings from respondent-driven sampling surveys
Authors: Barbaric Jelena , Bozicevic Ivana , Manathunge Ariyaratne , Gajaweera Chathrini , Beneragama Sriyakanthi
Published: August 2021

Background Biobehavioural data on transgender women (TGW) are limited globally. Methods: We used data collected as part of the 2017–18 National Integrated HIV Biobehavioural Survey, which included 254 TGW in Colombo and 252 in Jaffna, for structured questionnaire interviews and biological testing. We performed multivariable logistic regression analysis to explore factors associated with condom use. Results: We found low HIV prevalence in Colombo (0.6%) and no HIV infections in Jaffna. TGW in Colombo had higher positivity on the Treponema pallidum-particle agglutination test (2.5%) compared with TGW in Jaffna (0.4%). We found no hepatitis B infections. In both cities, <25% of TGW have comprehensive knowledge about HIV prevention. In Colombo 54.4%, but only 21.4% of TGW in Jaffna, have ever been tested for HIV. Drug-injecting behaviours are uncommon in both cities (prevalence <1%), whereas 7.4% reported sharing equipment for injecting feminising hormones in Colombo. Greater proportions of TGW in Colombo compared with Jaffna used condom at last sex (82.3% vs 37.7%). Multivariable analysis showed lower odds of condom use at last sex in TGW aged >30 years and those who did not test for HIV in the past 12 months in Colombo, and for TGW with higher income in Jaffna, TGW not visiting outdoor sites to find partners, and TGW who sold sex. Conclusions: Current burden of HIV, syphilis and hepatitis B among TGW in Sri Lanka is low. Although risk behavioural patterns vary between the cities, a substantial sexually transmitted infection vulnerability is a common denominator, calling for strengthening of the capacity to respond to specific TGW needs.
Interaction between decision-making and interoceptive representations of bodily arousal in frontal cortex
Authors: Fujimoto Atsushi , Murray Elisabeth A. , Rudebeck Peter H.
Published: August 2021

Significance

How bodily arousal states influence decision-making has been a central question in psychology, but the neural mechanisms are unclear. We recorded heart rate (HR), a measure of bodily arousal, while simultaneously monitoring neural activity in orbitofrontal cortex (OFC) and dorsal anterior cingulate cortex (dACC) of macaques making reward-guided decisions. In intact macaques, higher HR was associated with shorter reaction times. Concurrently, the activity of a set of neurons in OFC and dACC selectively encoded HR. Following amygdala lesions, HR generally increased, and now the relationship between HR and reaction times was altered. At the neural level, the balance of encoding in dACC shifted toward signaling HR, suggesting a specific mechanism through which bodily arousal influences decision-making.
Hierarchy of signaling thresholds downstream of the T cell receptor and the Tec kinase ITK
Authors: Gallagher Michael P. , Conley James M. , Vangala Pranitha , Garber Manuel , Reboldi Andrea , Berg Leslie J.
Published: August 2021

Significance

In order to help fight off pathogens and malignancies, CD8
+
T lymphocytes send signals from the T cell receptor (TCR) through multiple transcription factor pathways. The strength of the TCR signal is modulated in part by the Tec kinase ITK, whose activity helps create graded amounts of T cell activation genes. We report that some signaling pathways rely more heavily on ITK support for robust activation. During suboptimal signaling conditions, we measured the reduced amount of NF-κB activation and early gene induction within digital NFAT- and Erk1/2-activated cells. Our work highlights the importance of signal strength in activating T cells and uncovers details about the supplemental role of ITK in proximal TCR signaling.
Highly motile nanoscale magnetic artificial cilia
Authors: Islam Tanveer ul , Bellouard Yves , den Toonder Jaap M. J.
Published: August 2021

Significance

Cilia are hair-like microscopic structures present abundantly in our body and producing motions at the smallest scales. They perform a wide range of critical functions and are crucial for the normal functioning of our body. Abnormal functioning of cilia results in a number of diseases jointly known as ciliopathies. Artificially mimicking cilia is aimed at understanding their normal/abnormal functionality and at developing cilia-inspired micro-/nanoengineering devices. In this study, we present a magnetic polymer preparation process yielding a material with optimum properties and a cilia fabrication method producing the smallest highly motile artificial cilia with sizes equal to their biological counterparts. This opens avenues for biological studies and for creating submicrometer manipulation and control.
FtsA acts through FtsW to promote cell wall synthesis during cell division in
Escherichia coli
Authors: Park Kyung-Tae , Pichoff Sebastien , Du Shishen , Lutkenhaus Joe
Published: August 2021

Significance

A critical, but not well characterized, step in bacterial cell division is the activation of the FtsWI septal peptidoglycan (sPG) synthase at the Z-ring. In
Escherichia coli
, activation depends upon FtsN, which acts indirectly by activating FtsQLB in the periplasm and FtsA in the cytoplasm. Here, we show that an activated FtsA rescues FtsW recruitment and activation when the hierarchical pathway of recruitment is disrupted. Furthermore, an
ftsW
mutant was isolated that responds to a hyperactive FtsQLB but not to a hyperactive FtsA. Our results indicate an activated FtsA acts through FtsW and synergizes with an activated FtsL acting on FtsI to activate FtsWI within the divisome to synthesize sPG, resulting in cytokinesis.
Synchrony and diachrony of postverbal negation in Jodï-Sáliban
Authors: Rosés Labrada Jorge Emilio
Published: August 2021

This article proposes a detailed comparative treatment of negation in the Jodï-Sáliban language family (Venezuela-Colombia, Northwest Amazonia, South America), which consists of four languages: Jodï [yau], Sáliba [slc], Piaroa [pid] and Mako [wpc]. This comparative analysis of negation strategies across the four languages in the family not only offers an overview of negation strategies in this language family but also allows for conclusions to be drawn on the cognacy of the different constructions and markers as well as on the sources of the main negation strategies. Specifically, I show that, even though certain markers are not cognate, negation in these languages has – as far back as the documentation goes – always been postverbal and suggest that postverbal negation can be diachronically stable. This research thus offers an in-depth analysis of negation in Jodï-Sáliban, a language family that remains underdescribed, and, crucially, contributes to our understanding of postverbal negation and its sources.
A sustainable way of agricultural livelihood: edible bird’s nests in Indonesia
Authors: Ito Yutaka , Matsumoto Ken’ichi , Usup Aswin , Yamamoto Yuki
Published: August 2021

Edible birds’ nests (EBNs) have traditionally been produced in Southeast Asia. Indonesian farmers construct buildings for swiftlets and harvest their nests. EBN farming does not directly degrade forest resources and is therefore considered a sustainable means of production, whereas the expansion of other agricultural activities often relies on the degradation of natural resources. This study examines the relationship between natural resources and agricultural livelihoods, focusing on Indonesian EBN farmers. Using survey data that we collected in 2017, combined with satellite information on the extent of the forest in Central Kalimantan, Indonesia, we measured production efficiency and identified the natural and social factors that enhance production performance. The results show that a forest extent ranging between 2,000 and 6,000 meters from nesting building is positively associated with the production efficiency of EBN farming, perhaps because extensive forest could help swiftlets to collect food and build nests. Conversely, while EBN farming is a sustainable and profitable option, the initial costs of constructing buildings to house swiftlets may deter farmers from participating in the process.
The heat equation for nanoconstrictions in 2D materials with Joule self-heating
Authors: Ward Oliver M G , McCann Edward
Published: August 2021

We consider the heat equation for monolayer two-dimensional materials in the presence of heat flow into a substrate and Joule heating due to electrical current. We compare devices including a nanowire of constant width and a bow tie (or wedge) constriction of varying width, and we derive approximate one-dimensional heat equations for them; a bow tie constriction is described by the modified Bessel equation of zero order. We compare steady state analytic solutions of the approximate equations with numerical results obtained by a finite element method solution of the two-dimensional equation. Using these solutions, we describe the role of thermal conductivity, thermal boundary resistance with the substrate and device geometry. The temperature in a device at fixed potential difference will remain finite as the width shrinks, but will diverge for fixed current, logarithmically with width for the bow tie as compared to an inverse square dependence in a nanowire.
Partial structural order of gel-forming material detected as multimodal subdiffusion by logarithmic measure
Authors: Shimizu Yugo , Hanasaki Itsuo
Published: August 2021

Fibrous nanomaterials suspended in liquid form gel structures when the binding sites between the components reach sufficient number densities. Cellulose nanofibers (CNFs) are one of such nanomaterials, and transparent papers are fabricated by drying their aqueous dispersions. It is therefore important to characterize the wet state, but the specific fluorescent marker molecules are not available for arbitrary CNFs. We report an approach based on the single particle tracking of Brownian probe particles. We focus on the nonuniformity in the Brownian motion to detect the partial structural order between sol and gel, which is nontrivial to characterize. The simple logarithmic measure of diffusive behavior reveals the multimodal nature of Brownian motion depending on the CNF concentration. The subdiffusive behavior by the overall mean squared displacements alone does not tell whether it is caused by confinement in the local environment by CNFs, or binding to single CNFs possibly diffusing in the dispersion. However, the particle-size dependence clarifies that it is not caused by binding but the confinement effect. Furthermore, the logarithmic measure approach enables the detection of overlapping distributions through their heads rather than tails. The detection of partial structural order by rheological non-uniformity of the system with a simple approach will contribute to the further understanding of gel forming materials in general.
First principles studies of the electronic and structural properties of the rutile VO2(110) surface and its oxygen-rich terminations
Authors: Planer J , Mittendorfer F , Redinger J
Published: August 2021

We present a density functional theory (DFT) study of the structural and electronic properties of the bare metallic rutile VO2 (110) surface and its oxygen-rich terminations. Due to the polyvalent nature of vanadium and abundance of oxide phases, the modelling of this material on the DFT level remains a challenging task. We discuss the performance of various DFT functionals, including PBE, PBE + U (U = 2 eV), SCAN and SCAN + rVV functionals with non-magnetic and ferromagnetic spin ordering, and show that the calculated phase stabilities depend on the chosen functional. We predict the presence of a ring-like termination that is electronically and structurally related to an insulating V2O5 (001) monolayer and shows a higher stability than pure oxygen adsorption phases. Our results show that employing the spin-polarized SCAN functional offers a good compromise, as it offers both a reasonable description of the structural and electronic properties of the rutile VO2 bulk phase and the enthalpy of formation for oxygen rich vanadium phases present at the surface.
The impact of training sample size on deep learning-based organ auto-segmentation for head-and-neck patients
Authors: Fang Yingtao , Wang Jiazhou , Ou Xiaomin , Ying Hongmei , Hu Chaosu , Zhang Zhen , Hu Weigang
Published: August 2021

To investigate the impact of training sample size on the performance of deep learning-based organ auto-segmentation for head-and-neck cancer patients, a total of 1160 patients with head-and-neck cancer who received radiotherapy were enrolled in this study. Patient planning CT images and regions of interest (ROIs) delineation, including the brainstem, spinal cord, eyes, lenses, optic nerves, temporal lobes, parotids, larynx and body, were collected. An evaluation dataset with 200 patients were randomly selected and combined with Dice similarity index to evaluate the model performances. Eleven training datasets with different sample sizes were randomly selected from the remaining 960 patients to form auto-segmentation models. All models used the same data augmentation methods, network structures and training hyperparameters. A performance estimation model of the training sample size based on the inverse power law function was established. Different performance change patterns were found for different organs. Six organs had the best performance with 800 training samples and others achieved their best performance with 600 training samples or 400 samples. The benefit of increasing the size of the training dataset gradually decreased. Compared to the best performance, optic nerves and lenses reached 95% of their best effect at 200, and the other organs reached 95% of their best effect at 40. For the fitting effect of the inverse power law function, the fitted root mean square errors of all ROIs were less than 0.03 (left eye: 0.024, others: <0.01), and the R square of all ROIs except for the body was greater than 0.5. The sample size has a significant impact on the performance of deep learning-based auto-segmentation. The relationship between sample size and performance depends on the inherent characteristics of the organ. In some cases, relatively small samples can achieve satisfactory performance.
Rise and fall of laser-intensity effects in spectrally resolved Compton process
Authors: Acosta U Hernandez , Titov A I , Kämpfer B
Published: August 2021

The laser intensity dependence of nonlinear Compton scattering is discussed in some detail. For sufficiently hard photons with energy ω′, the spectrally resolved differential cross section dσ/dω′|
ω′=const, rises from small toward larger laser intensity parameter ξ, reaches a maximum, and falls toward the asymptotic strong-field region. Such a rise and fall of a differential observable is to be contrasted with the monotonously increasing laser intensity dependence of the total probability, which is governed by the soft spectral part. We combine that hard-photon yield from Compton scattering with the seeded Breit–Wheeler pair production in a folding model and obtain a rapidly increasing e
+
e
− pair number at ξ ≲ 4. Laser bandwidth effects are quantified in the weak-field limit of the related trident pair production.
Study on a novel vertical enhancement-mode Ga
2
O
3
MOSFET with FINFET structure
Authors: Guo Liangliang , Zhang Yuming , Luan Suzhen , Qiao Rundi , Jia Renxu
Published: August 2021

A novel enhanced mode (E-mode) Ga2O3 metal–oxide–semiconductor field-effect transistor (MOSFET) with vertical FINFET structure is proposed and the characteristics of that device are numerically investigated. It is found that the concentration of the source region and the width coupled with the height of the channel mainly effect the on-state characteristics. The metal material of the gate, the oxide material, the oxide thickness, and the epitaxial layer concentration strongly affect the threshold voltage and the output currents. Enabling an E-mode MOSFET device requires a large work function gate metal and an oxide with large dielectric constant. When the output current density of the device increases, the source concentration, the thickness of the epitaxial layer, and the total width of the device need to be expanded. The threshold voltage decreases with the increase of the width of the channel area under the same gate voltage. It is indicated that a set of optimal parameters of a practical vertical enhancement-mode Ga2O3 MOSFET requires the epitaxial layer concentration, the channel height of the device, the thickness of the source region, and the oxide thickness of the device should be less than 5 × 1016 cm−3, less than 1.5 μm, between 0.1 μm − − 0.3 μm and less than 0.08 μm, respectively.
Three-step self-calibrating generalized phase-shifting interferometry
Authors: Zhang Yu
Published: August 2021

An accurate and fast three-step self-calibrating generalized phase-shifting interferomertry (SGPSI) is proposed. In this approach, two new phase-shifting signals are constructed by the difference interferograms normalization and noise suppressing, then the unknown phase shift between the two difference phase-shifting signals is estimated quickly through searching the minimum coefficient of variation of the modulation amplitude, a limited number of pixels are selected to participate in the search process to further save time, and finally the phase is reconstructed through the searched phase shift. Through the reconstruction of phase map by the simulation and experiment, and the comparison with several mature algorithms, the good performance of the proposed algorithm is proved, and it eliminates the limitation of requiring more than three phase-shifting interferograms for high-precision SGPSI. We expect this method to be widely used in the future.
30 glitches in 18 radio pulsars
Authors: Liu Hong-Yi , Zhou Shi-Qi , Zhang Yu-Qi , Feng Zhong-Wen , Zhou Xia
Published: August 2021

Pulsar timing is a classic technology of detecting irregularities in pulsar rotation. We carried out this method for 18 young radio pulsars, with long-term timing observations obtained between 2007 and 2015 using the Parkes 64-m radio telescope. As a result, 30 glitches were identified, ranging from 0.75 × 10−9 to 8.6 × 10−6 in the relative glitch sizes Δν/ν, where ν = 1/P is the pulse frequency. These glitches are composed of 26 new glitches and four published glitches with new exponential recoveries. All pulsars exhibit normal glitches, and six pulsars were observed to undergo a glitch event for the first time. We discuss the properties and implications for neutron-star physics of these glitches, and show that they are in agreement with previous work, except that the cumulative probability distributions of the mean waiting times for PSRs J0537–6910, J1341–6220 and J1740–3015 are not in consonance with the Poisson model.
Exploring the characteristics of the flare from PMN J0218–2307 by Fermi-LAT
Authors: Xiang Yun-Chuan , Xin Yu-Liang , Yuan Min
Published: August 2021

PMN J0218–2307 (4FGL J0218.9–2305) is classified as a blazar candidate with unknown type (BCU) in the fourth source catalog from the Fermi Large Area Telescope (Fermi-LAT). With the updated Fermi-LAT Pass 8 data, the γ-ray flaring activity toward PMN J0218–2307 is detected. The test statistic (TS) value of PMN J0218–2307 in energy band of 100 MeV–500 GeV is 133.893 with a significance level of 10.96σ. The maximum-likelihood photon flux is (8.131 ± 1.359) × 10−9 ph cm−2 s−1. A significant γ-ray flare in the period from 2008 August 4 to 2019 August 25 is found from the source. The spectral characteristics of GeV energy band of PMN J0218–2307 is similar to that of flat-spectrum radio quasars (FSRQs) in the local Universe.
A preliminary study on photogrammetry for the FAST main reflector measurement
Authors: Li Wei-Min , Zhou Liu-Jian
Published: August 2021

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is the largest single-dish radio telescope in the world. In this paper, we apply photogrammetry to measure local area surface accuracy of the FAST main reflector. Contrast with the existing photogrammetric methods that need to stick the cooperation target on the panel. In this paper, we directly detect nodes according to their natural feature. Analyzing the FAST reflector composition, we propose a two-step Hough transform method for node detection. Due to the high similarity of the neighboring area around nodes, it is hard to match two images by the feature matching method. Therefore, we apply the nodes combination approach to obtain the homography matrix between two photos for nodes matching. After nodes detection and matching, triangulation and bundle adjustment algorithms are adopted for 3D reconstruction. During the experiment, the adjusted node position deform a local area of the FAST main reflector into a spherical cap with a radius of 300 m. The experimental result shows that the measurement accuracy of the sphere with a radius of 300 m is 12.299 mm, indicating that it is feasible to apply photogrammetry for the FAST main reflector measurement.
Research on actuator distribution and panels for a radio telescope
Authors: Wang Jin-Qing , Sun Zheng-Xiong , Fu Li , Li Jin-Ling , Yu Lin-Feng , Jiang Yong-Chen , Jiang Yong-Bin , Gou Wei , Hu Wei , Zhao Rong-Bin , Liu Qin-Hui , Shen Zhi-Qiang
Published: August 2021

Trying to achieve the best surface accuracy control with the fewest actuators, this article mainly studies the distribution of actuators and the method of panel design. The influence of the number of faulty actuators on the accuracy of the surface shape is demonstrated. In addition, the method incorporating a triangular panel, node index and the fitting solution method of a single panel is also given. This method provides a reference for the design and realization of an active surface or a deformable sub-reflector for high performance large aperture radio telescopes.
A novel method for telescope polarization modeling based on an artificial neural network
Authors: Peng Jian-Guo , Yuan Shu , Ji Kai-Fan , Xu Zhi
Published: August 2021

The polarization characteristics of an astronomical telescope is an important factor that affects polarimetry accuracy. Polarization modeling is an essential means to achieve high precision and efficient polarization measurement of the telescope, especially for the alt-azimuth mount telescope. At present, the polarization model for the telescope (i.e., the physical parametric model) is mainly constructed using the polarization parameters of each optical element. In this paper, an artificial neural network (ANN) is used to model the polarization characteristics of the telescope. The ANN model between the physical parametric model residual and the pointing direction of the telescope is obtained, which reduces the model deviation caused by the incompleteness of the physical parametric model. Compared with the physical parametric model, the model fitting and predictive accuracy of the New Vacuum Solar Telescope (NVST) is improved after adopting the ANN model. After using the ANN model, the polarization cross-talk from I to Q, U, and V can be reduced from 0.011 to 0.007, and the crosstalk among Q, U, and V can be reduced from 0.047 to 0.020, which effectively improves the polarization measurement accuracy of the telescope.
DeepSun: machine-learning-as-a-service for solar flare prediction
Authors: Abduallah Yasser , L. Wang Jason T. , Nie Yang , Liu Chang , Wang Haimin
Published: August 2021

Solar flare prediction plays an important role in understanding and forecasting space weather. The main goal of the Helioseismic and Magnetic Imager (HMI), one of the instruments on NASA’s Solar Dynamics Observatory, is to study the origin of solar variability and characterize the Sun’s magnetic activity. HMI provides continuous full-disk observations of the solar vector magnetic field with high cadence data that lead to reliable predictive capability; yet, solar flare prediction effort utilizing these data is still limited. In this paper, we present a machine-learning-as-a-service (MLaaS) framework, called DeepSun, for predicting solar flares on the web based on HMI’s data products. Specifically, we construct training data by utilizing the physical parameters provided by the Space-weather HMI Active Region Patch (SHARP) and categorize solar flares into four classes, namely B, C, M and X, according to the X-ray flare catalogs available at the National Centers for Environmental Information (NCEI). Thus, the solar flare prediction problem at hand is essentially a multi-class (i.e., four-class) classification problem. The DeepSun system employs several machine learning algorithms to tackle this multi-class prediction problem and provides an application programming interface (API) for remote programming users. To our knowledge, DeepSun is the first MLaaS tool capable of predicting solar flares through the internet.
Physical and geometrical parameters of CVBS XIV: the two nearby systems HIP 19206 and HIP 84425
Authors: Al-Wardat Mashhoor A. , Abu-Alrob Enas , Hussein Abdallah M. , Mardini Mohammad K. , Taani Ali A. , Widyan Hatem S. , Yousef Zahraa T. , Al-Naimiy Hamid M. , Yusuf Nihad A.
Published: August 2021

Data release 2 (DR2) from the Gaia mission was of great help in precise determination of fundamental parameters of Close Visual Binary and Multiple Systems (CVBMSs), especially masses of their components, which are crucial parameters in understanding formation and evolution of stars and galaxies. This article presents the complete set of fundamental parameters for two nearby close visual binary systems (CVBSs), which are HIP 19206 and HIP 84425. We utilised a combination of two methods; the first one is Tokovinin’s dynamical method to solve the orbit of the system and to estimate orbital elements and the dynamical mass sum, and the second one is Al-Wardat’s method for analysing CVBMSs to estimate the physical parameters of the individual components. The latest method employs grids of Kurucz line-blanketed plane parallel model atmospheres to build synthetic Spectral Energy Distributions (SEDs) of the individual components. Trigonometric parallax measurements given by Gaia DR2 and Hipparcos catalogues are used to analyse the two systems. The difference in these measurements yielded slight discrepancies in the fundamental parameters of the individual components, especially masses. So, a new dynamical parallax is suggested in this work based on the most convenient mass sum as given by each of the two methods. The new dynamical parallax for the system HIP 19205 of 22.97 ± 0.95 mas coincides well with the trigonometric one reported recently (in December 2020) by Gaia EDR3 of 22.3689 ± 0.4056 mas. The positions of the components of the two systems on the evolutionary tracks and isochrones are plotted, which suggest that all components are solar-type main sequence stars. Their most probable formation and evolution scenarios are also discussed.
A novel stellar spectrum denoising method based on deep Bayesian modeling
Authors: Kang Xin , He Shi-Yuan , Zhang Yan-Xia
Published: August 2021

Spectrum denoising is an important procedure for large-scale spectroscopical surveys. This work proposes a novel stellar spectrum denoising method based on deep Bayesian modeling. The construction of our model includes a prior distribution for each stellar subclass, a spectrum generator and a flow-based noise model. Our method takes into account the noise correlation structure, and it is not susceptible to strong sky emission lines and cosmic rays. Moreover, it is able to naturally handle spectra with missing flux values without ad-hoc imputation. The proposed method is evaluated on real stellar spectra from the Sloan Digital Sky Survey (SDSS) with a comprehensive list of common stellar subclasses and compared to the standard denoising auto-encoder. Our denoising method demonstrates a superior performance to the standard denoising auto-encoder, in respect of denoising quality and missing flux imputation. It may be potentially helpful in improving the accuracy of the classification and physical parameter measurement of stars when applying our method during data preprocessing.
A method for pulsar searching: combining a two-dimensional autocorrelation profile map and a deep convolutional neural network
Authors: Wang Long-Qi , Jin Jing , Liu Lu , Shen Yi
Published: August 2021

In pulsar astronomy, detecting effective pulsar signals among numerous pulsar candidates is an important research topic. Starting from space X-ray pulsar signals, the two-dimensional autocorrelation profile map (2D-APM) feature modelling method, which utilizes epoch folding of the autocorrelation function of X-ray signals and expands the time-domain information of the periodic axis, is proposed. A uniform setting criterion regarding the time resolution of the periodic axis addresses pulsar signals without any prior information. Compared with the traditional profile, the model has a strong anti-noise ability, a greater abundance of information and consistent characteristics. The new feature is simulated with double Gaussian components, and the characteristic distribution of the model is revealed to be closely related to the distance between the double peaks of the profile. Next, a deep convolutional neural network (DCNN) is built, named Inception-ResNet. According to the order of the peak separation and number of arriving photons, 30 data sets based on the Poisson process are simulated to construct the training set, and the observation data of PSRs B0531+21, B0540-69 and B1509-58 from the Rossi X-ray Timing Explorer (RXTE) are selected to generate the test set. The number of training sets and the number of test sets are 30 000 and 5400, respectively. After achieving convergence stability, more than 99% of the pulsar signals are recognized, and more than 99% of the interference is successfully rejected, which verifies the high degree of agreement between the network and the feature model and the high potential of the proposed method in searching for pulsars.
The research objectives and observational possibilities for fast moving near-Earth asteroids
Authors: Pomazan Anton , Tang Zheng-Hong , Maigurova Nadiia , Tang Kai , Yu Yong , Mao Yin-Dun
Published: August 2021

The paper describes observations of fast-moving near-Earth asteroids (NEAs) made with the small ground-based telescopes of National Time Service Center of Chinese Academy of Science (NTSC of CAS) and Research Institute “Mykolaiv Astronomical Observatory” (RI MAO) by the rotating-drift-scan CCD (RDS CCD) technique. This technique is used to obtain the point images of both the studied objects and reference stars. The results of ongoing follow-up observations of NEAs are discussed. The residual differences (O – C) between the observed and calculated positions from JPL ephemeris were generally small for these asteroids. The standard deviations of these differences were typically ±(0.2″ – 0.3″) in both coordinates for objects with apparent velocity which substantially exceed FWHM for the given exposure time. The results of comparative statistics for such observations from the MPC database show that this is a good level of precision for NEAs. Moreover, the telescopes with the RDS CCD technique implemented can observe the NEAs that closely approach the Earth and with enough observations can improve the precision of determining their orbital elements and impact predictions.
The deep and low-mass-ratio contact binary CSS J022914.4+044340 with a luminous additional companion
Authors: Liu Liang , Li Xu-Zhi
Published: August 2021

The firstB-,V-,Rc- andIc-band light curves of CSS J022914.4+044340 are presented and analyzed. It is found that CSS J022914.4+044340 is a low mass ratio (0.198 ± 0.005) deep (63.7 ± 7.9%) contact binary, indicating that it is already at the end evolutionary stage of tidally-locked evolution via magnetized wind. Because of the totally eclipsing character, the photometric solutions are reliable. The temperature and metallicity are determined from the spectroscopic data asT= 5855 ± 15 K and [Fe/H] = –0.842 ± 0.031, respectively. Based on the parallax ofGaiaEDR3, the physical parameters of CSS J022914.4+044340 are estimated asM1=1.44−0.22+0.25M⊙,M2=0.29−0.05+0.05M⊙,R1=1.26−0.06+0.08R⊙,R2=0.65−0.04+0.03R⊙,L1=1.718−0.191+0.186L⊙andL2=0.416−0.050+0.039L⊙. Combining the fraction of light from the third body via the photometric solution (54%), the luminosity of the third body is estimated as 2.705L⊙. The third body may be inferred to be a subgiant. Thus, why the primary component of CSS J022914.4+044340 has higher mass compared to similar systems is explained, as well as why its metallicity is so poor.
A low-cost and high-performance technique for adaptive optics static wavefront correction
Authors: Ren De-Qing , Zhang Tian-Yu , Wang Gang
Published: August 2021

Non-Common Path Error (NCPE) is one of the factors that limit an Adaptive Optics (AO) system from delivering ultra-high performance. To correct the NCPE associated static aberration, we propose a simple but robust and high-performance pupil-plane based wavefront measurement and correction technique, which can copy a single-mode fiber generated perfect wavefront to the AO system via an iteration optimization process, and the NCPE can be effectively corrected by directly commanding the Deformable Mirror (DM) of the AO system. Compared with the previous focal-plane based approach that uses focal plane based Point Spread Function (PSF) for correction evaluation, the pupil-plane based approach can be reliably and rapidly converged to a global optimization result and provides better performance, in particular for an AO system with a large initial static wavefront error. This technique we proposed can be implemented in astronomical AO systems where extremely high performance is required.
Ultra-low noise L-band cryogenic astronomical receiver for the FAST telescope
Authors: Liu Hong-Fei , He Chuan , Wang Jin , Jiang Peng , Wang Sheng-Wang , Wu Yang , Zhang Hang , Song Jin-You , Shi Xiang-Wei , Guo Ming-Lei
Published: August 2021

This paper presents an ultra-low noise L-band radio astronomical cryogenic receiver for the Five-hundred-meter Aperture Spherical radio Telescope (FAST) telescope. The development of key low noise microwave parts of coupling low noise amplifier (Coupling-LNA) and conical quad-ridge orthogonal mode transducers (OMT) and reasonable system integration achieve outstanding performance of receiver. It covers the frequency range of 1.2 GHz to 1.8 GHz. Novel cryogenic Coupling-LNAs with low noise, large return loss, high dynamic range and the function of coupling calibration signals are developed for the proposed receiver. Amplification and coupling function circuits are integrated as a single Coupling-LNA with full noise temperature of 4 K at the physical temperature of 15 K. Its return loss is more than 18 dB, and output 1 dB compression power is +5 dBm. A cryogenic dewar is fabricated to provide 55 K and 15 K cryogenic environment for OMT and Coupling-LNAs, respectively. The receiver’s system noise temperature is below 9 K referred to feed aperture plane. Benefiting from optimal design and precise mechanical treatment, good scattering performance of OMT and equalized radiation patterns of horn are achieved with an antenna efficiency above 75%.
Predicting the 25th solar cycle using deep learning methods based on sunspot area data
Authors: Li Qiang , Wan Miao , Zeng Shu-Guang , Zheng Sheng , Deng Lin-Hua
Published: August 2021

It is a significant task to predict the solar activity for space weather and solar physics. All kinds of approaches have been used to forecast solar activities, and they have been applied to many areas such as the solar dynamo of simulation and space mission planning. In this paper, we employ the long-short-term memory (LSTM) and neural network autoregression (NNAR) deep learning methods to predict the upcoming 25th solar cycle using the sunspot area (SSA) data during the period of May 1874 to December 2020. Our results show that the 25th solar cycle will be 55% stronger than Solar Cycle 24 with a maximum sunspot area of 3115±401 and the cycle reaching its peak in October 2022 by using the LSTM method. It also shows that deep learning algorithms perform better than the other commonly used methods and have high application value.
Axisymmetric Drop Shape Analysis using a low-cost home-made setup
Authors: Guilizzoni Manfredo , Sapienza Jessica
Published: August 2021

Surface science and engineering gained an increasing importance in recent years, due to the potential benefit they can offer in many applications. An important parameter in this field is the surface wettability, that is in general evaluated by the contact angle. One of the most accurate techniques to measure this quantity is the axisymmetric drop shape analysis, based on the fitting of the theoretical Laplace-Young profile to the contour of experimental drops. In this paper the performance of a simple, low-cost setup – that can be built “at home” – to apply this technique is assessed, also including a detailed analysis about the influence of the most important parameters to set in the procedure. The latter aspect was evaluated by using computer-generated drop profiles and pictures, to have “realistic” images, but for drops of known properties. The experimental setup was built using a desk, a table lamp, a medical syringe, a support for the samples and a “bridge” camera. Measurements were performed on smooth and rough textile surfaces and the results were compared with previous measurements taken with a professional setup. From the comparison it can be affirmed that the performance of the home-made setup is very satisfactory.
Vision based quality control of composite components: considerations about measurement accuracy
Authors: D’Emilia Giulio , Gaspari Antonella , Natale Emanuela , Ubaldi Davide
Published: August 2021

In this paper a methodology is discussed concerning the measurement of yarn’s angle of a reinforced polypropylene matrix used in the production of automotive components. The measurement method is based on a vision system and advanced processing of images in order to evaluate the geometrical parameters of interest; the accuracy of measurement is a mandatory requirement, in order to assess the simulation approach for thermoplastic process optimization. Many aspects influencing the whole accuracy of the method have been identified and their effect evaluated, of both geometrical and optical type, allowing to perform angle measurements of the fiber angle with a whole accuracy in the order of a few degrees. By this way both local and extended defects can be identified in a reliable way also with reference to components of complex geometry. According to these results, accurate measurements of angle allows us to both validate the simulation of the thermoplastic process and to give suggestions for process improvement of fiber glass components of complex geometry.
Dancing with Multiple Stub, Discontiguous Areas, and routing protocols of OSPF in IXP
Authors: Oo Tun Tun , Africa Aaron Don M. , Navea Roy Francis
Published: August 2021

This Research paper implemented the stability of OSPF LSAs-types in IXP by utilizing the complexity area with a high-speed data rate. The multiple stubs, discontiguous areas, and multiple routing protocols are deployed to be intended for ISP/IXP. When the stubby which managed the entering external or internal information database of LSA are analyzed and changed the LSAs-types, router types, and routing protocol. And then, the redistribution or External summary are applied to communicate different Routing Information protocol as (IGP, EGP). The RIPv2 and EIGRP routing protocol are configured to examine the external routing protocol. Furthermore, Totally NSSA and the Totally stubs operations are described as a coherent system in this system. The end-to-end throughputs are better improved, after using a stub, NSSA. And then, the security of routing information is safe and some IP was been the hidden system for each section. The OSPF algorithm with SPF is link update and boost routing information protocol table, database system.