bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensitivity kernels in seismic wave propagation: a simplified explanation for the banana-doughnut paradox
Authors: Ciardelli Caio
Published: April 2022

Ray theory, a high-frequency approximation to describe wave propagation, has been a cornerstone in seismology for over a hundred years. Despite its simplicity and wide range of applications, some limitations combined with the ever-increasing computational power motivated the development of finite-frequency theory, a better model to describe how the Earth’s inner structure affects seismic waves. Finite-frequency theory has matured a lot in the last decades, and it is now widely applied in many geophysical problems. However, most students and even some experienced researchers face difficulties understanding it. An appropriate theoretical comprehension is paramount to making the most out of the methods a theory underpins, avoiding pushing it beyond its limits, and further developing it. With that problem in mind, this paper shows a simplified formulation of the sensitivity kernels, which are the generalization of rays in the finite-frequency regime. The resultant model, despite its limitations, correctly predicts the main features of finite-frequency theory, including the zero sensitivity in the middle of the travel-time kernels, known as the banana-doughnut paradox, shedding new light on that intriguing phenomenon. The step-by-step derivation and relatively easy equations should be understandable by an undergraduate student with a reasonable knowledge of classical physics and calculus. A Colab Notebook implementing the main formulas accompanies the paper, allowing readers to interact and play with the results.
Structural, dynamic, and hydration properties of quercetin and its aggregates in solution
Authors: Campo M G , Corral G M
Published: April 2022

Quercetin is a flavonoid present in the human diet with multiple health benefits. Quercetin solutions are inhomogeneous even at very low concentrations due to quercetin’s tendency to aggregate. We simulate, using molecular dynamics, three systems of quercetin solutions: infinite dilution, 0.22 M, and 0.46 M. The systems at the two highest concentrations represent regions of the quercetin aggregates, in which the concentration of this molecule is unusually high. We study the behavior of this molecule, its aggregates, and the modifications in the surrounding water. In the first three successive layers of quercetin hydration, the density of water and the hydrogen bonds formations between water molecules are smaller than that of bulk. Quercetin has a hydrophilic surface region that preferentially establishes donor hydrogen bonds with water molecules with relative frequencies from 0.12 to 0.46 at infinite dilution. Also, it has two hydrophobic regions above and below the planes of its rings, whose first hydration layers are further out from quercetin (≈0.3 Å) and their water molecules do not establish hydrogen bonds with it. Water density around the hydrophobic regions is smaller than that of the hydrophilic. Quercetin molecules aggregate in π-stacking configurations, with a distance of ≈0.37 nm between the planes of their rings, and form bonds between their hydroxyl groups. The formation of quercetin aggregates decreases the hydrogen bonds between quercetin and the surrounding water and produces a subdiffusive behavior in water molecules. Quercetin has a subdiffusive behavior even at infinite dilution, which increases with the number of molecules within the aggregates and the time they remain within them.
Perspectives on tolerability and reasonableness
Authors: Ban N , Boyd M , Coates R , Cool D A , Lecomte J-F , Schneider T
Published: April 2022

Judgements on tolerability and reasonableness are central to the optimisation of protection. There are currently several international developments regarding these key considerations which will contribute to the review and evolution of the system of radiological protection. The IRPA15 International Congress brought together the principal issues currently under discussion, and the outcome of these discussions is presented.
Factors affecting dose-length product of computed tomography component in whole-body positron emission tomography/computed tomography
Authors: Inoue Yusuke , Takahashi Keita , Miyatake Hiroki , Nagahara Kazunori , Iwasaki Rie
Published: April 2022

In whole-body positron emission tomography (PET)/computed tomography (CT), it is important to optimise the CT radiation dose. We have investigated factors affecting the dose-length product (DLP) of the CT component of whole-body PET/CT and derived equations to predict the DLP. In this retrospective study, 1596 whole-body oncology PET/CT examinations with 18F-fluorodeoxyglucose were analysed. Automatic exposure control was used to modulate radiation dose in CT. Considering age, weight, sex, arm position (up, down, one arm up), scan range (up to the mid-thigh or feet), scan mode (spiral or respiratory-triggered nonspiral) and the presence of a metal prosthesis as potential factors, multivariate analysis was performed to identify independent predictors of DLP and to determine equations to predict DLP. DLP values were predicted using the obtained equations, and compared with actual values. Among body size indices, weight best correlated with DLP in examinations performed under the standard imaging conditions (arms: up; scan range: up to the mid-thigh; scan mode: spiral; and no metal prosthesis). Multivariate analysis indicated that weight, arm position, scan range and scan mode were substantial independent predictors; lowering the arms, extending the scan range and using respiratory-triggered imaging, as well as increasing weight, increased DLP. The degree of the DLP increase tended to increase with increasing weight. The DLP values were predicted using equations that considered these parameters were in excellent agreement with the actual values. The DLP for the CT component of whole-body PET/CT is affected by weight, arm position, scan range and scan mode, and can be predicted with excellent accuracy using these factors.
Multi-layer adaptive convolutional neural network unsupervised domain adaptive bearing fault diagnosis method
Authors: Cui Jie , Li Yanfeng , Zhang Qianqian , Wang Zhijian , Du Wenhua , Wang Junyuan
Published: April 2022

Deep learning provides a feasible fault diagnosis method for intelligent mechanical systems. However, this method requires a large amount of marking data, which greatly limits its application in the actual industry. Therefore, this paper proposes a multi-layer adaptive convolutional neural network unsupervised domain adaptive bearing fault diagnosis method (MACNN), which is especially suitable for bearing fault classification under variable working conditions. First, a new method to improve domain alignment is proposed (LD-CORAL). This method uses Log-Euclidean distance to measure deep coral loss, which solves the problem that the covariance matrix cannot be aligned correctly in the manifold structure. Then, it proposes multi-layer adaptation of LD-CORAL loss in the fully connected layer, and combines center-based discriminative loss to improve the feature learning ability of the model, which can improve the classification accuracy and domain adaptation performance of the model. Finally, in order to verify the effectiveness and feasibility of the proposed method, the method is applied to the multi-fault diagnosis of gearbox bearings under variable working conditions. Comparing the classification results of different methods, the conclusion shows that this method is more effective for bearing fault classification under variable working conditions.
Optimization and application of the concentric conductance probes in liquid film thickness measurement in a helically coiled tube
Authors: Liu Shuai , Liu Li , Gu Hanyang , Wang Ke
Published: April 2022

The liquid film distribution in the helically coiled tube (HCT) is affected by curvature-induced centrifugal force and gravity force, showing more complex characteristics than straight tubes. However, due to the limitation of the measurement technology, the relevant data on liquid film in HCT are still rare. In this paper, based on the time-multiplexed excitation-probing scheme, a type of non-intrusive concentric conductance probes (CCPs) is developed at first. After reporting the operation principle of CCPs, the numerical simulation of potential field distribution in CCPs is conducted, and the effects of electrode structure parameters and liquid film thickness on the performance of CCPs are then analyzed in detail. It is found that in a certain range, the larger the inner electrode and outer electrode diameter, the greater the signal penetration depth (i.e. the larger the measurement range of liquid film thickness). Finally, the spatio-temporal distribution of liquid film on the wall of the HCT is experimentally studied using the optimized CCPs. The results indicate that this probe can realize the high-frequency accurate capture of liquid film flow details such as the occurrence and evolution process of liquid film inversion and the fluctuation characteristics of liquid film in HCT. The wave frequency of the liquid film is demonstrated to be not consistent along the circumferential direction. Using Strouhal number and Lockhart–Martinelli parameter, the wave frequency correlation at the maximum film thickness in the state of film inversion in HCT is obtained.
Microplasma emission spectroscopy of stable isotope ratios in carbon dioxide
Authors: Persson Anders
Published: April 2022

This study investigates the prospects of using emissions from the discharge of a stripline split-ring resonator microplasma source to measure the 13C/12C isotope ratio in CO2. The plasma source was used in a measurement scheme called microplasma emission spectroscopy, in which the visible emission spectrum of the CO2 discharge was investigated using a Charge-Coupled Device (CCD) spectrometer. The study revealed that the major isotope dependencies of the spectrum originated from the Ångström system (B
1Σ+ → A
1Π) of CO molecules that had been converted from CO2 in the discharge. Although at least four of the bands of the Ångström system showed clear isotopic dependences, the (0–3) band at 561 nm was concluded to show the most prospects for spectrometric applications because of a combination of wide isotopic shift and low background. A theoretical model of this band was constructed and used in a partial least squares fitting algorithm, to quantify the abundance of 12C and 13C in the sample. This signal processing method was shown to be robust and linear over the whole dynamic range of 13C/12C ratios (1%–100%) but required a ten-fold improvement in precision and accuracy at naturally occurring 13C levels (1.07%–1.12%) to be useful in most scientific applications. However, several promising ways of achieving such an improvement have been presented, and the results demonstrate the potential of creating a simple, cost-effective, and highly miniaturized system for isotope ratio measurements, which could offer great advantages to scientists in many different fields, from environmental science to planetary exploration.
Calculations of the AC losses in superconducting cables and coils: Neumann boundary conditions of the T–A formulation
Authors: Wang Sijian , Yong Huadong , Zhou Youhe
Published: April 2022

Numerical techniques play an important role in the design of high-temperature superconductor (HTS) systems. In the superconductivity community, the T–A formulation of Maxwell’s equations and its homogeneous technique have become popular in recent years. The T–A formulation has the capability of simulating HTS systems and high computational efficiency. However, it is still difficult for the T–A formulation to solve some special problems. For instance, the net current is not explicitly known in each HTS tape. In the present work, the contributions of the Neumann boundary condition are studied, which represent a coupling effect between the T and the A formulations. This paper firstly describes the Neumann boundary condition in detail. Then, based on the T–A formulation and its Neumann boundary condition, the non-uniform current distribution in the cables and the current decay in the closed-loop coils are respectively analyzed. This method can solve the difficulties of the T–A formulation in calculating some specific problems, and extend the application range of the T–A formulation. Furthermore, the above supplement is also applicable to the homogeneous and the three-dimensional (3D) models.
Effects of tidal charge on magnetic reconnection and energy extraction from spinning braneworld black hole
Authors: Wei Shao-Wen , Wang Hui-Min , Zhang Yu-Peng , Liu Yu-Xiao
Published: April 2022

Recent study shows that the magnetic reconnection can serve as an efficient mechanism to extract energy from rapidly spinning black holes. In this paper, we consider the effects of the tidal charge on the energy extraction via the magnetic reconnection in the backgrounds of a spinning braneworld black hole. With the increase of the tidal charge, we find that both the energies of the accelerated plasma and decelerated plasma decrease for the observer located at infinity. To achieve the purpose extracting the net energy from the black hole, the decelerated plasma should take negative energy. Then we observe that the power of the energy extraction via the magnetic reconnection grows with the tidal charge. Meanwhile, the efficiency also increases with the tidal charge indicating that the spinning braneworld black hole with positive tidal charge is more efficient than the Kerr black hole. Compared with the Blandford-Znajek mechanism, the magnetic reconnection process shall have a higher power for positive tidal charge. These results indicate that the tidal charge has a significant effect on the energy extraction via the magnetic reconnection process.
Confronting quantum-corrected teleparallel cosmology
with observations
Authors: Bernardo Reginald Christian , Chen Che-Yu , Levi Said Jackson , Kung Yu-Hsien
Published: April 2022

It has been shown that at the semi-classical order, gravitational theories with quantum fluctuations can be effectively recast as modified theories of gravity with non-minimal gravity-matter couplings. We proceed from an observational perspective and see whether such quantum fluctuations can leave imprints on the late Universe. Within the teleparallel formulation, we investigate a representative model in this general class of modified gravitational theories inlaid with quantum fluctuations, and determine the cosmological parameters by using compiled late-time data sets. Furthermore, we assess the statistical significance of such quantum corrections compared to the standard cosmological model. The results mildly favor the inclusion of quantum corrections with a negative density parameter supporting a phantom-like dark energy. This edge is not sufficient to rule out either models but it supports the consideration of quantum corrections in a cosmological setting.
The Sensitivity of GPz Estimates of Photo-z Posterior PDFs to Realistically Complex Training Set Imperfections
Authors: Stylianou Natalia , Malz Alex I. , Hatfield Peter , Crenshaw John Franklin , Gschwend Julia
Published: April 2022

The accurate estimation of photometric redshifts is crucial to many upcoming galaxy surveys, for example, the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). Almost all Rubin extragalactic and cosmological science requires accurate and precise calculation of photometric redshifts; many diverse approaches to this problem are currently in the process of being developed, validated, and tested. In this work, we use the photometric redshift code GPz to examine two realistically complex training set imperfections scenarios for machine learning based photometric redshift calculation: (i) where the spectroscopic training set has a very different distribution in color–magnitude space to the test set, and (ii) where the effect of emission line confusion causes a fraction of the training spectroscopic sample to not have the true redshift. By evaluating the sensitivity of GPz to a range of increasingly severe imperfections, with a range of metrics (both of photo-z point estimates as well as posterior probability distribution functions, PDFs), we quantify the degree to which predictions get worse with higher degrees of degradation. In particular, we find that there is a substantial drop-off in photo-z quality when line-confusion goes above ∼1%, and sample incompleteness below a redshift of 1.5, for an experimental setup using data from the Buzzard Flock synthetic sky catalogs.
Wayne State University’s Dan Zowada Memorial Observatory: Characterization and Pipeline of a 0.5 m Robotic Telescope
Authors: Carr Robert , Cinabro David , Cackett Edward , Moutard David , Carroll Russell
Published: April 2022

Wayne State University’s Dan Zowada Memorial Observatory is a fully robotic 0.5 m telescope and imaging system located under the dark skies of New Mexico. The observatory is particularly suited to time domain astronomy: the observation of variable objects, such as tidal disruption events, supernovae, and active galactic nuclei. We have developed a software suite for image reduction, alignment and stacking, and calculation of absolute photometry in the Sloan filters used at the telescope. Our pipeline also performs image subtraction to enable photometry of objects embedded in bright backgrounds such as galaxies. The 5σ detection limit of the Zowada Observatory for integration of 16 × 90 s exposures is 19.0 mag in g-band, 18.1 mag in r-band, 17.9 mag in i-band, and 16.6 mag in z-band. For a 3σ detection limit, measurements may be performed with greater uncertainties as deep as 19.9, 19.1. 18.9 and 17.5 mag in griz bands, respectively.
A three-cornered hat analysis of instabilities in two-way and GPS carrier phase time transfer systems
Authors: Parker T E , Zhang V , Petit G , Yao J , Brown R C , Hanssen J L
Published: April 2022

A three-cornered hat analysis has been performed on three independent time transfer systems between the United States Naval Observatory (USNO) and the National Institute of Standards and Technology (NIST). These include (1) a direct Two-Way Satellite Time and Frequency Transfer (TWSTFT) link provided by the USNO, (2) an indirect TWSTFT link, and (3) GPS carrier phase (GPSCP) links. Time transfer instabilities for individual links, as quantified with the time deviation and TOTAL time deviation, have been measured for the first time for averaging periods between 2 h and 85 days. Time transfer instabilities beyond one day are roughly flicker phase in nature and generally range between 40 ps and 120 ps. Frequency transfer instabilities, as quantified by the modified Allan deviation, are observed to be as low as 1 × 10−16 for a 20 day comparison and into the mid 10−17 range at longer comparison times.
Cortical complexity and connectivity during isoflurane-induced general anesthesia: a rat study
Authors: Wang Zhijie , Zhang Fengrui , Yue Lupeng , Hu Li , Li Xiaoli , Xu Bo , Liang Zhenhu
Published: April 2022

Objective. The investigation of neurophysiologic mechanisms of anesthetic drug-induced loss of consciousness (LOC) by using the entropy, complexity, and information integration theories at the mesoscopic level has been a hot topic in recent years. However, systematic research is still lacking. Approach. We analyzed electrocorticography (ECoG) data recorded from nine rats during isoflurane-induced unconsciousness. To characterize the complexity and connectivity changes, we investigated ECoG power, symbolic dynamic-based entropy (i.e. permutation entropy (PE)), complexity (i.e. permutation Lempel-Ziv complexity (PLZC)), information integration (i.e. permutation cross mutual information (PCMI)), and PCMI-based cortical brain networks in the frontal, parietal, and occipital cortical regions. Main results. Firstly, LOC was accompanied by a raised power in the ECoG beta (12–30 Hz) but a decreased power in the high gamma (55–95 Hz) frequency band in all three brain regions. Secondly, PE and PLZC showed similar change trends in the lower frequency band (0.1–45 Hz), declining after LOC (p < 0.05) and increasing after recovery of consciousness (p < 0.001). Thirdly, intra-frontal and inter-frontal-parietal PCMI declined after LOC, in both lower (0.1–45 Hz) and higher frequency bands (55–95 Hz) (p < 0.001). Finally, the local network parameters of the nodal clustering coefficient and nodal efficiency in the frontal region decreased after LOC, in both the lower and higher frequency bands (p < 0.05). Moreover, global network parameters of the normalized average clustering coefficient and small world index increased slightly after LOC in the lower frequency band. However, this increase was not statistically significant. Significance. The PE, PLZC, PCMI and PCMI-based brain networks are effective metrics for qualifying the effects of isoflurane.
Influence of porosity and blistering on the thermal fatigue behavior of tungsten
Authors: Li Y. , Vermeij T. , Hoefnagels J.P.M. , Zhu Q. , Morgan T.W.
Published: April 2022

Tungsten is the leading plasma-facing material (PFM) for nuclear fusion applications. It faces severe operating conditions, including intense hydrogen plasma exposure and high-cycle transient heat loading, which create various defects in tungsten. Additionally, defects have often already been introduced during manufacturing. Little is understood regarding the synergistic effect of such defects on the lifetime of tungsten so far. Here, we investigate the influence of porosity and blistering on the thermal fatigue behavior of tungsten. The pores resulted from powder metallurgy whereas the blistering was induced by hydrogen plasma exposure. Both conditions were subjected to transient heat loading by a high-power pulsed laser. The exposure was performed in the linear plasma generator Magnum-PSI, which closely mimics the expected particle and heat flux in the world’s largest fusion experiment, ITER. Both porosity and blistering degraded the fatigue resistance of tungsten. Pores tended to aggregate at high-angle grain boundaries (HAGBs) and assisted crack initiation therein, as revealed by focused ion beam cross-sectioning and electron backscatter diffraction (EBSD) analysis. The blisters were characteristic of subsurface cavities, which were located at a depth close to the surface roughness induced by transient heat loading. The stress concentration at the tip of the cavities is considered to promote crack initiation. The results highlight the necessity of a ‘life cycle assessment’ of the tungsten PFM for nuclear fusion reactors.
Manufacturing completion of the first ITER vacuum vessel sector
Authors: Kim H.S. , Moon H.K. , Park C.K. , Jung Y.J. , Ha M.S. , Park S.H. , Joo Y.M. , Joo J.K. , Kang S.G. , Seo Y.H. , Han J.Y. , Lim N.J. , Yoon B.H. , Choi S.Y. , Hwang H.S. , Hong K.H. , Ahn H.J. , Lee Y.J. , Kim B.C. , Lee H.G. , Jung K.J. , Sa J.W. , Choi C.H. , Chung W.H. , Kim H.K. , Kim Y.G. , Kim G.H. , Hong Y.S. , Martinez J.M. , Martin A. , Jing J. , Privalov M. , Xiang B. , Lobinger F. , Pedrosa N. , Rodilla E. , Utin Y. , Mestric A. , Jung Y.S. , Tok J.Y.W. , Park K.H. , Kim H.C. , Seok S.H. , Park D.B. , Moon G.H. , Lee J.H. , Lim K.S. , Kim J.B. , Yeo H.K. , Lee J.J.
Published: April 2022

In April 2020, manufacturing of the ITER vacuum vessel (VV) first sector has been completed by the Korean domestic agency, manufacturing having started in February 2012. The ITER VV sector is the largest fusion VV structure in the world. Each step of the manufacturing was a challenge as a first-of-a-kind, and a French nuclear pressure vessel. The paper provides an overview of the major challenges which were overcome over the last 10 years.
A deterministic method for the fast evaluation and optimisation of the 3D neutron wall load for generic stellarator configurations
Authors: Lion Jorrit , Warmer Felix , Wang Huaijin
Published: April 2022

The neutronic assessment of a fusion power plant design is usually a challenging and time-consuming task involving experts from several disciplines in order to assemble the geometry, source, as well as carry out computationally heavy Monte Carlo transport simulations. In order to overcome this challenge, we present in this work a deterministic method, which combines all these aspects in a single framework that can directly calculate a key neutronics performance indicator, the neutron wall load (NWL), at minimal computational cost for arbitrary stellarator configurations. As our method is based on simple vector and matrix manipulations, a speed on the order of a few CPU-seconds is achieved, which makes it suitable for optimisation frameworks. We demonstrate with a simple optimisation algorithm that it is possible to use our method to generate a first wall with reduced ‘heterogeneity’ in the NWL distribution.
Quantum states from mixtures of equilibrium distributions
Authors: Mintchev Mihail
Published: April 2022

We construct and explore a family of states for quantum systems in contact with two or more heath reservoirs. The reservoirs are described by equilibrium distributions. The interaction of each reservoir with the bulk of the system is encoded in a probability, which characterises the particle exchange among them and depends in general on the particle momentum. The convex combination of the reservoir distributions, weighted with the aforementioned probabilities, defines a new distribution. We establish the existence of an emission–absorption regime in which the new distribution generates a non-equilibrium quantum state. We develop a systematic field theory framework for constructing this state and illustrate its physical properties on a simple model. In this context we derive the particle current full counting statistics, the heat current and the Lorenz number. The entropy production and the relative quantum fluctuations are also determined.
Effect of rear wall inclination on cavity acoustic characteristics at high Mach numbers
Authors: Tang Yin , Luo Lei , Zhang Peihong , Ma Mingsheng
Published: April 2022

Cavity flow has been a research hotspot in aerodynamics. Cavities with low Mach numbers have been extensively investigated, while those with high Mach numbers have been less explored. In this study, a flow control method specific to the acoustic characteristics of an open-type cavity with a high Mach number was studied through the improved delayed detached eddy simulation (IDDES). Next, the rear wall of the cavity was inclined to mitigate the impact strength formed by the airflow on the rear wall surface, thus reaching the goal of reducing the aerodynamic noise in the cavity. The Mach number and length-to-depth ratio of the cavity were calculated as 3.51 and 4.5, respectively. The calculation results manifested that under a high Mach number, the sound pressure level (SPL) at the bottom of the cavity and that at its front wall surface could be obviously reduced by inclining the rear wall, and the reduction amplitude increased with the increase in the inclination angle. At the inclination angle of 60°, the SPL at the bottom could be reduced by 24 dB at maximum.
Belt grinding method considering outer profile and inner wall thickness
Authors: Huang Yun , Wei Ming , Xiao GuiJian , Liu Shuai
Published: April 2022

Increasing thrust-to-weight ratio is the goal pursued by aero-engines. Aero-engine blades are the core components of aero-engines. In order to reduce the weight and improve the thrust-to-weight ratio, the cavity structure is gradually applied to aero-engine blades. The constraints of the outer contour and the inner wall thickness of the cavity structure blade make its trajectory planning difficult, which seriously affects its surface roughness and profile accuracy. In this study, proposes a titanium alloy blade surface machining method based on belt grinding, which is constrained by two dimensions of contour and wall thickness, and the process parameters of titanium alloy material specimens are studied. The obtained parameters are applied to the blade grinding process, the grinding trajectory is planned, and finally parameters of the blade are tested. The processing and testing results verify the effectiveness of the method in this paper.
Structure Design and Optimization of a gas turbine blade
Authors: Qian Zhengming , Li Gaiqi
Published: April 2022

Aiming at the fatigue life failure of a gas turbine blade, an optimization design of the blade was performed based on the test phenomenon and results of fatigue life analysis. As a result, the stress of the blade is decreased, and the fatigue life of the blade is increased.
Analysis of retraction performance of aircraft landing gear in high and low temperature environment
Authors: Wu JingTao , Tian PeiQiang , Cheng Zhu , Deng WenLiang
Published: April 2022

In order to solve the problem that the internal mechanism parameters of the aircraft landing gear are difficult to measure and retractable, the retractable performance of the landing gear under high and low temperature environments is studied. This paper simplifies the retractable mechanism of the landing gear by analyzing the motion mechanism of the aircraft landing gear. The degree of freedom of the retractable mechanism is calculated to verify the accuracy of the simplified rear landing gear retraction mechanism. The simulation model of landing gear retraction mechanism under high and low temperature environment is constructed by Patran. The component deformation and shaft clearance of the retractable mechanism under low temperature (-55°C) and high temperature (74°C) environments are analyzed from the overall and detail dimensions. The quantitative effect of ambient temperature on the deformation of the retractable mechanism of the landing gear is studied. Then Adams is used to establish the kinematics simulation model of the retractable mechanism, and the friction coefficient of the kinematic pair under different ambient temperatures is incorporated. Based on the historical data of the high and low temperature environmental test of the landing gear, the correctness of the model is verified. The influence of the environmental temperature on the driving torque, movement angle and movement time of the retractable mechanism is quantified. The problem that the deformation parameters and motion characteristics of the retractable mechanism of the landing gear are difficult to measure is solved, and the research method of retractable performance of the landing gear mechanism under different ambient temperatures is formed.
Investigation on impact resistance of hierarchical lightweight lattice structure
Authors: Gan Jiakang , Ji E , Li Bing
Published: April 2022

This paper is majorly discussing the impact resistance of hierarchical lightweight lattice structure. Firstly, the unit cells of hierarchical pyramidal lattice structure and traditional single-stage hollow pyramidal lattice structure are designed. At the same time, the concept of relative density is introduced to better demonstrate the impact resistance of hierarchical structure. In this paper, ABAQUS/Explicit software is used to simulate the drop hammer impact simulation of hierarchical structure and hollow structure. The result shows that the impact resistance of hierarchical structure is better than hollow structure. Meanwhile, the samples are prepared by 3D printing, and then quasi-static compression experiment and drop hammer impact experiment are carried out. It is concluded that the bearing and impact resistance performance of the hierarchical structure has obvious improvement than the hollow structure under both quasi-static compression and low-speed drop hammer impact.
Design of Wireless Charging Coils for Aero-engine Telemetry Information Transmission System
Authors: Li Ze , Ouyang Yunfang , Huang Zhou , Zhang Quanxin
Published: April 2022

In order to meet the need of non-contact transmission of aero-engine telemetry information, first of all, a rotor disk and a stator disk suitable for near field communication are designed in this paper, then, the coil design of wireless charging system suitable for high centrifugal force load is carried out. The designed single charging coil can charge two receiving coils at the same time. In order to eliminate the influence of aluminum alloy rotor disk and stator disk on charging performance, concave ferrite slots are installed on rotor disk and stator disk respectively to shield charging coil and receiving coil. The designed charging coils are fabricated and integrated with rotor disk and stator disk respectively. Finally, the designed charging coil and receiving coils are connected into the charging system for testing. The test results show that the charging coil and receiving coils are completely matched with the charging circuit and receiving circuit, and their performance can fully meet the use requirements of aeroengine telemetry information transmission system.
Design of Transmitting Antenna for Aero-engine Telemetry Information Transmission System
Authors: Li Ze , Ouyang Yunfang , Huang Zhou , Zhang Quanxin
Published: April 2022

The demand of aero-engine for non-contact telemetry information transmission is very urgent. Based on the analysis of the characteristics of aero-engine telemetry information transmission system, the rotor disk and stator disk suitable for near-field communication under high centrifugal load are designed in this paper. In order to ensure the stable transmission of telemetry information under large angular displacement between rotor disk and stator disk, two circular arc-shaped dipole antennas are designed to be symmetrically installed on rotor disk for telemetry information transmission. The designed pair of arc-shaped dipole antennas are fabricated and measured. The measurement results show that the two transmitting antennas resonate at 2.19GHz and 2.27GHz respectively, and their impedance bandwidth of -10dB is 35MHz and 34mhz respectively. In their operating frequency band, the isolation between them is greater than 38dB, and their performance fully meets the needs of aeroengine telemetry information transmission.
Performance Analysis of Satellite Navigation Positioning Service under Ionospheric Scintillation
Authors: Zhu Wendan , Zhong Lunlong , Li Yupeng
Published: April 2022

Satellite navigation signals may be affected by ionospheric anomalies such as ionospheric scintillation and ionospheric storms. These anomalies will lead to fluctuations and delays of signals, and thus affecting the performance of satellite navigation service. How to evaluate the performance of satellite navigation service under the influence of ionospheric anomaly is one of the key issues to ensure the safety of satellite navigation aviation service. To solve this problem, the simulation of satellite navigation signals under scintillation and the performance evaluation of positioning service are studied in this paper. Firstly, the scintillation sequence is simulated based on Cornell model. Then, the influence of scintillation on satellite signal parameters is modeled and a generation approach of intermediate frequency satellite navigation signals under scintillation is proposed. Finally, the performance indicators of normal signal and scintillating signal are quantitatively analyzed by solving the navigation parameters and evaluating the performance indicators of the receiver. Simulation results show that the ionospheric scintillation affects the satellite navigation service performance, with reference to the standard specification requirements. Performance of satellite navigation positioning service is severely affected even only one satellite signal is affected by a common moderate scintillation level.
Research on Aerodynamic Modeling of Axisymmetric Aircraft Based on Orthogonal Least Squares
Authors: Wang Jianqi , Wang Dongmei , Zhang Yunyuan
Published: April 2022

Aerodynamic modeling is of great importance for design of axisymmetric aircraft control system. In this paper, an axisymmetric aircraft aerodynamic model selection method is constructed, which involves an orthogonal least squares algorithm using in model structure selection, and the method based on it is selected for determining the aerodynamic coefficients. Then the method is tested in three axis coefficient modeling of a certain axisymmetric aircraft, and the modeling result is consistent with the wind tunnel test data.
Research on visualization and diagnosis method of civil aircraft WQAR data
Authors: Ren Chenhui , Ma Linlong , Yang Xu , Wan Junlong
Published: April 2022

WQAR data has the characteristics of large scale, high dimension and many random interference factors, which makes it extremely difficult to use WQAR operational data for flight quality monitoring, expert unknown anomaly detection and PHM. This paper proposes a civil aircraft WQAR data visualization display scheme and the overall framework of fault diagnosis adopts a two-stage cycle to research and recycle and improve the data preprocessing requirements, visualization and diagnostic process methods, etc., and use the civil aircraft operation data to verify the proposed theoretical model and diagnose the failure status. Results shown that the theoretical framework and method can accurately predict the health status of aircraft engines, and can effectively solve the problems of high dimension and many interference factors of WQAR data.
Design of Aeronautical Digital Video and Communication Bus Processing System
Authors: Zhu Pengcheng , Li Haojie
Published: April 2022

With the development of avionics systems, Avionics Digital Video Bus (ARINC 818) and Digital Information Transmission System (Arinc429) have become a new generation of aviation video transmission and communication bus standard respectively. Aiming at the characteristics of ARINC 818 and Arinc429, an aeronautical digital video and communication bus processing system is designed. First, the ARINC 818 aviation video transmission bus and the Arinc429 communication bus standard are introduced. Then, the design principles of the aeronautical digital video and communication bus processing system are described according to this standard, and the design scheme of each system component is introduced in detail. Finally, build a hardware test platform for testing and verification. The system development follows an integrated and modular design, with the Application Processing Unit (APU) main processor and Field Programmable Gate Array (FPGA) as the core, which realizes the superposition of 1-channel input ARINC 818 video with internally generated characters, and then outputs 1-channel ARINC 818 to the function displayed on the display. At the same time, it supports 7-channel Electronic Industries Association-422 (EIA-422) and 4-channel Arinc429 bus communication. In addition, the system supports the processing of 22 input discrete quantities and 7 input analog quantities. The design has been successfully used in a certain type of aircraft display control management system.
Aviation application of dual-weighted neural network based on biomimetic pattern recognition
Authors: Zhao Xue
Published: April 2022

In order to solve the difficult problem of fault diagnosis in aviation equipment, this paper uses a biomimetic pattern recognition method. Compared to traditional pattern recognition, biomimetic pattern recognition is able to construct closed, complex geometries to cover all kinds of samples. Biomimetic pattern recognition is a “cognitive” approach, where the process between two similar things is considered asymptotic. It mathematically means that all similar samples in the feature space are continuously indistinguishable. The paper establishes a dual-weighted neural network model of an aircraft auxiliary power unit. Comparing the diagnostic process and results with traditional manual neural networks. The results show that biomimetic pattern recognition is a feasible and efficient diagnostic method for the fault diagnosis of aviation equipment. It provides a new way of thinking and method for the practical application of aviation equipment fault diagnosis.
Laminar Flow Control using an Optimised Forward-Facing Step - An Experimental Approach
Authors: Gao Chunyi , Yadav Devinder Kumar , Bhatia Dinesh
Published: April 2022

With the rapid increase of global aviation emissions, biomimetics has proven to be a promising avenue to achieve greener aviation. This paper aims to explore the influence of the shark skin denticle inspired two-dimensional Forward-Facing Steps (FFS) on boundary-layer transition delay and drag reduction. Previous computation simulations indicate that the presence of FFS inside the laminar boundary layer can damp disturbances and lead to transition delay and drag reduction. The purpose of this paper is to find the optimal configuration of the FFS through experimental tests and correlate results to previously concluded simulations. Conditional results indicate that the presence of the FFS within the laminar boundary layer is effective in transition delay and drag reduction.
Probabilistic Collision-free Pattern Control For Large-Scale Spacecraft Swarms Around Circular Orbits
Authors: Chen Lin , Wang Chi , Yang Chihang , Deng Hong , Zhang Hao
Published: April 2022

This work considers controlling large-scale spacecraft swarms to achieve complex spatial configuration. A novel distributed guidance algorithm is proposed based on Inhomogeneous Markov Chains, Probabilistic Density Guidance and Voronoi partition (IMC-PDG-Voronoi) algorithms. The physical space is partitioned into multiple bins and the density distribution of the swarm is controlled via a probabilistic approach. Then the modified Voronoi partition method is used to generate a collision-free trajectory for each agent. To apply the probabilistic control algorithm to circular Earth orbit, the periodic solution of the Clohessy-Wiltshire (C-W) equation in configuration space is transformed into a parameter space. Then a convex optimization open-loop controller with minimum fuel consumption in LVLH coordinates is designed to control the swarm to expected positions. Numerical simulations show that the algorithm can effectively guide and control large-scale spacecraft swarms to form complex configurations on circular orbits, with high precision and little cost.
Global environmental controls on wildfire burnt area, size, and intensity
Authors: Haas Olivia , Prentice Iain Colin , Harrison Sandy P
Published: April 2022

Fire is an important influence on the global patterns of vegetation structure and composition. Wildfire is included as a distinct process in many dynamic global vegetation models but limited current understanding of fire regimes restricts these models’ ability to reproduce more than the broadest geographic patterns. Here we present a statistical analysis of the global controls of remotely sensed burnt area (BA), fire size (FS), and a derived metric related to fire intensity (FI). Separate generalized linear models were fitted to observed monthly fractional BA from the Global Fire Emissions Database (GFEDv4), median FS from the Global Fire Atlas, and median fire radiative power from the MCD14ML dataset normalized by the square root of median FS. The three models were initially constructed from a common set of 16 predictors; only the strongest predictors for each model were retained in the final models. It is shown that BA is primarily driven by fuel availability and dryness; FS by conditions promoting fire spread; and FI by fractional tree cover and road density. Both BA and FS are constrained by landscape fragmentation, whereas FI is constrained by fuel moisture. Ignition sources (lightning and human population) were positively related to BA (after accounting for road density), but negatively to FI. These findings imply that the different controls on BA, FS and FI need to be considered in process-based models. They highlight the need to include measures of landscape fragmentation as well as fuel load and dryness, and to pay close attention to the controls of fire spread.
A Swanson-like Hamiltonian and the inverted harmonic oscillator
Authors: Bagarello Fabio
Published: April 2022

We deduce the eigenvalues and the eigenvectors of a parameter-dependent Hamiltonian H

θ
which is closely related to the Swanson Hamiltonian, and we construct bi-coherent states for it. After that, we show how and in which sense the eigensystem of the Hamiltonian H of the inverted quantum harmonic oscillator can be deduced from that of H

θ
. We show that there is no need to introduce a different scalar product using some ad hoc metric operator, as suggested by other authors. Indeed we prove that a distributional approach is sufficient to deal with the Hamiltonian H of the inverted oscillator.
Dynamic control of Fano resonances in a coupled dual microring resonator system
Authors: Lu Chunyu , Alaydrus Musa , Nikbakht Hamed , Akca B Imran
Published: April 2022

We propose a coupled optical microresonator system that can be used as a new and flexible platform to form asymmetric Fano-like resonances and dynamically control their line shapes and frequencies. The coupled microresonator system was formed using two microring resonators coupled via a 3 × 3 coupler. The upper microring resonator is the add-drop type, whereas the lower one is the all-pass type, providing the (semi-) continuum and discrete states, respectively. We simulated the behavior of the coupled system using the finite-difference time-domain method and observed asymmetric Fano line shapes in the transmission spectra. We demonstrated that the line shapes and frequencies of Fano resonances can be controlled by dynamically varying the refractive index of a small region of the upper or lower microring resonators. We also introduced a small gap in the upper microring resonator to control the continuum state more efficiently. The proposed coupled microresonator concept is simple, easy to fabricate and sufficiently flexible to be engineered for different applications.
Recent advances in wearable exoskeletons for human strength augmentation
Authors: Lee Jinwoo , Kwon Kangkyu , Yeo Woon-Hong
Published: April 2022

The decline in muscular strength and control due to age or stroke-related side-effect has afflicted many individuals with neuromotor disorders because it affects essential motor functions to perform everyday activities and restrains their functional independence. In this regard, a myriad of wearable exoskeletons and functional components have been developed to deliver mechanical force for assisting the movements of different human body parts. However, many of the reported wearable exoskeletons suffer from several critical drawbacks that limit functional usage and practicality despite the significant technological advance of general wearable exoskeletons. Here, this review offers a comprehensive summary of the recent advances of wearable exoskeletons and their constituting functional components. In addition, we discuss the essential challenges that need to be tackled to enhance the functional practicality of the next-generation wearable exoskeletons in assisting the strength and control of individuals with neuromotor disorders.