分类： 能源科学 >> 储能技术 提交时间： 2024-03-31
摘要： This work experimentally explores the influence of thesodiumchloride pollution on thePEMFC performancein the marine saltsprayenvironment by analyzing the concentration diffusion characteristics of the sodium chloride in thePEMFC membraneelectrodes. Firstly, a set of experiments were carried out to determine the distribution of the sodium chloride components in the membrane electrodes, where five different salt spray environments (i.e., 100mg/L, 200mg/L, 300mg/L, 400mg/L, and 500mg/L of the salt component, respectively) were used/employed to analyze the concentration diffusion characteristics of the sodium chloride. Then, the obtained samples were microscopically characterized and elementally analyzed by thefield emission scanning electron microscopy(FESEM) and the energy spectrometry. Subsequently, a least squares-based model was proposed to predict the diffusion rate of the contaminatingions inthe membrane electrodes. Lastly, the pollution of the sodium chloride was evaluated/assessed to reveal theperformance degradationof the PEMFCs. The experimental results demonstrated that (1) the sodium chloride fraction existed as crystals orions inthe membrane electrodes in the marine salt spray environment; (2) the sodium chloride poisoning was founded in theproton exchange membranein the form ofsodium ions; (3) and the sodium-to-chloride ratio was proportional to the contamination time and the salt spray in the proton exchange membrane.
分类： 机械工程 >> 刀具技术 提交时间： 2024-03-31
Nikodem Wrobel
Michal Rejek
Jolanta Krolczyk
Mateusz Franka
Munish K. Gupta
Marcin Sliwinski
Grzegorz Krolczyk
Z. Li
摘要： The present article describes a new and innovative method of producing an inseparablejointwith the use of expansion jaws. The effect of jaw tool geometry on the reaction forces and ultimate strength of an inseparable joint formed on a prototype stand was analyzed. The results are also compared of joints produced by jaws with single movement method and with complex movement method. The tool responds with bending and pressing one part into the other, which results in their permanent connection. In the tests, differentiation was introduced with regard to the height of the applied force to the collar of the connection pipe. A novelty is also a solution based on a complex, parameterized trajectory of the stamp movement consisting of horizontal and vertical displacements. This paper presents the tests of the joints formed at the stand. The new approach described in this article has resulted in a joint strength increase of approximately 30% using the innovative complex jaw movement of the biaxial clinching process. A jointtensile strengthclose to 1000N was achieved.
分类： 交通运输工程 >> 水路运输 提交时间： 2024-03-31
摘要： The ship motion perception approaches mainly use maritime radar, Automatic Identification System (AIS) and cameras. However, using either of these approaches alone may result in information inconsistency and insufficient data accuracy. Therefore, a multi-sensor fusion perception system is proposed in this study to monitor ship motion in inland waterways. Firstly, a hardware platform of multi-sensor fusion ship motion perception system composed of maritime radar, AIS, cameras and other accessories is constructed. Secondly, by utilizing the target detection and tracking algorithms, track association algorithms, the ship motion data collected from the three sensors are integrated. Finally, the performance of the ship motion perception system is verified by field experiments in day and night. The experimental results indicate that the integrated ship motion perception system with multiple sensors is able to improve the information consistency and data accuracy of ship motion apparently in inland waterway compared to other perception systems.
分类： 机械工程 >> 机械设计 提交时间： 2024-03-31
摘要： The bottom pivot is a vital support device in the miter gate but often subject to poor lubrication and wear failures. Calculating thehydrodynamic lubricationcharacteristics of the bottom pivot is a complex three-dimensional (3D) problem, and most of existing models adopt simplified assumptions to reduce the calculation difficulty. To solve this issue, this work develops a 3D model to calculate thehydrodynamic lubricationcharacteristics of the miter gate bottom pivot. Thefinite difference methodis used to solve theoil film thicknessand pressure distribution based on the spherical coordinatesReynolds equation. The component forces in three directions are calculated from the pressure distribution and compared with the theoretical values to generate the calculation difference. Then, thegenetic algorithm(GA) is used to minimize the difference to determine the optimal initial parameters for the 3D model. The analysis results show that the calculation accuracy can be significantly improved by using the optimal initial model parameters. When our initial pressure is 5.64MPa, the results meet the engineering accuracy requirements.
分类： 天文学 >> 天文学 提交时间： 2024-03-30
Niankun Yu
Zheng Zheng
Chao-Wei Tsai
Pei Zuo
Sara L. Ellison
David V. Stark
Di Li
Jingwen Wu
Karen L. Masters
Ting Xiao
Yinghui Zheng
Zongnan Li
Kai Zhang
Hongying Chen
Shu Liu
Sihan Jiao
Fanyi Meng
摘要： The atomic-to-molecular gas conversion is a critical step in the baryon cycle of galaxies, which sets the initial conditions for subsequent star formation and influences the multi-phase interstellar medium. We compiled a sample of 94 nearby galaxies with observations of multi-phase gas contents by utilizing public H I, CO, and optical IFU data from the MaNGA survey together with new FAST H I observations. In agreement with previous results, our sample shows that the global molecular-to-atomic gas ratio ($R_{\rm mol} \equiv$ log $M_{\rm H_2}/M_{\rm H\ I}$) is correlated with the global stellar mass surface density $\mu_*$ with a Kendall's $\tau$ coefficient of 0.25 and $p < 10^{-3}$, less tightly but still correlated with stellar mass and NUV$-$ r color, and not related to the specific star formation rate (sSFR). The cold gas distribution and kinematics inferred from the H I and CO global profile asymmetry and shape do not significantly rely on $R_{\rm mol}$. Thanks to the availability of kpc-scale observations of MaNGA, we decompose galaxies into H II, composite, and AGN-dominated regions by using the BPT diagrams. With increasing $R_{\rm mol}$, the fraction of H II regions within 1.5 effective radius decreases slightly; the density distribution in the spatially resolved BPT diagram also changes significantly, suggesting changes in metallicity and ionization states. Galaxies with high $R_{\rm mol}$ tend to have high oxygen abundance, both at one effective radius with a Kendall's $\tau$ coefficient of 0.37 ($p < 10^{-3}$) and their central regions. Among all parameters investigated here, the oxygen abundance at one effective radius has the strongest relation with global $R_{\rm mol}$, but the dependence of gas conversion on gas distribution and galaxy ionization states is weak.
分类： 信息科学与系统科学 >> 信息科学与系统科学基础学科 分类： 计算机科学 >> 计算机科学技术其他学科 分类： 工程与技术科学 >> 工程数学 提交时间： 2024-03-30
摘要： 什么是智能？是人工智能的核心问题之一，但是至今没有一个公认的定义。本文从智能与生命的关系视角提出：智能是生物体的基本能力和特征属性，是一种尽量用最小能量实现最大信息量，通过信息处理来适应环境、维持存在的能力。在此基础上，提出了智能是物质能量与信息之间的相互转换能力这一新观点，进一步提出了智能的测度计算方法、平均智能、综合智能等新概念，最后讨论了物质、能量与信息的定量转换关系，指出了智能的上界和能量转换为信息的下界，为便于实际应用，进一步给出一个无量纲的智能测度计算公式。为智能系统定量分析智能的高低给出了可行的计算方法。
分类： 天文学 >> 天文学 提交时间： 2024-03-29
摘要： 针对长期有争议的万有引力问题,论述了空间物体从小、大至星体的发展是以物体的转动惯量(I)为特征的自然进化过程.用时间、路径、质量三个因素说明I这一特征:时间说明I物体从小至今的持续时长;路径说明I是一种自然匀速行进的惯性物体,但在行进中其惯性作用在空间产生了以空间介质为媒介的惯介力矩,该力矩通过空间介质与另一物体产生关联逐渐形成了椭圆轨道;质量说明了质量的变化情况,在I与其他物体关联后会渐渐地归并另外物体,使其质量增加，则I相应增强. 给出了两个在空间相关星体的惯量平衡方程,由方程解出两物体的空间平衡点,通过地球、月球系统的真实数据和平衡点数据获得双方对应的运行轨迹、用以测定两者的紧密程度的刚性惯力与惯介力的比值、和两个星体的加速度原理及各自加速度计算值,经比对证明惯动平衡方程的正确性.这一成果对进一步理解太阳系的惯性特征将会有很大的促进作用.
分类： 核科学技术 >> 粒子加速器 提交时间： 2024-03-29
摘要： 自成靶中子管具有高耐温、高稳定性和长寿命的优点，在核测井领域的应用前景广阔。开展自成靶中子管中子产额模拟研究，可为中子管物理设计提供依据。基于TARGET程序，利用厚靶条件下D-T反应积分中子产额与T-D反应积分中子产额的关系，建立了一种T-D反应的等效模拟方法，实现了自成靶中子管中子产额的模拟计算。利用该方法，计算并分析了自成靶中子管束流参数和靶参数对中子产额的影响。结果表明，当入射束流的D、T混合比例为1:1时，自成靶中子管的中子产额取到最大值，增加或减小D的占比都会降低中子产额；靶原子比、束流能量、束流的单原子离子占比等参数与中子产额正相关，要提高自成靶中子管的中子产额，应在中子管设计限制条件下尽可能提高以上参数。
分类： 心理学 >> 发展心理学 提交时间： 2024-03-29
摘要： 父母教养和儿童行为存在密不可分的双向作用，但少有研究在微观层面检验亲子互动进程中的儿童驱动效应与父母驱动效应。本研究考察了113对5~6岁学龄前儿童及其家长在冲突对话中的行为表现，基于贝叶斯统计构建动态结构方程模型，捕捉实时互动引发的父母教养行为和儿童行为反应的变化，并通过回归分析考察父母和儿童行为对对话结局的影响。结果发现：(1)儿童在15s间隔内的消极行为反应能够正向预测随后15s父母的非支持性教养行为；(2)儿童的积极行为反应对对话结局起主要预测作用，儿童行为反应的积极水平越高，越有助于冲突的建设性解决。这些结果从微观层面验证了儿童驱动效应，强调了儿童反应在亲子互动中的重要作用。
分类： 天文学 >> 天文学 提交时间： 2024-03-29 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： To solve the problem of time-consuming measurement and correction of large antennas' reflector deformation, a new microwave holography methodology based on a Phased Array Feed (PAF) is proposed. Starting from the known expression of receiving signals in microwave holography, the theory of PAF holography is derived through Geometrical Optics. Reflector deformation, as well as pointing deviation and subreflector offset, can be calculated out by applying the derived equations. A measurement and correction system based on PAF holography is depicted, and two kinds of measurement methods are illustrated. The proposed measurement methodology is verified by numerical simulation, and its measurement error is analyzed. The results indicate that our proposed methodology is feasible, especially for Cassegrain antennas.
分类： 天文学 >> 天文学 提交时间： 2024-03-29 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： Pulsar search is always the basis of pulsar navigation, gravitational wave detection and other research topics. Currently, the volume of pulsar candidates collected by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) shows an explosive growth rate that has brought challenges for its pulsar candidate filtering system. Particularly, the multi-view heterogeneous data and class imbalance between true pulsars and non-pulsar candidates have negative effects on traditional single-modal supervised classification methods. In this study, a multi-modal and semi-supervised learning based on a pulsar candidate sifting algorithm is presented, which adopts a hybrid ensemble clustering scheme of density-based and partition-based methods combined with a feature-level fusion strategy for input data and a data partition strategy for parallelization. Experiments on both High Time Resolution Universe Survey II (HTRU2) and actual FAST observation data demonstrate that the proposed algorithm could excellently identify pulsars: On HTRU2, the precision and recall rates of its parallel mode reach 0.981 and 0.988 respectively. On FAST data, those of its parallel mode reach 0.891 and 0.961, meanwhile, the running time also significantly decreases with the increment of parallel nodes within limits. Thus, we can conclude that our algorithm could be a feasible idea for large scale pulsar candidate sifting for FAST drift scan observation.
分类： 天文学 >> 天文学 提交时间： 2024-03-29 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： We present an independent catalog (FRIIRGcat) of 45,241 Fanaroff–Riley Type II (FR-II) radio galaxies compiled from the Very Large Array Faint Images of the Radio Sky at Twenty-centimeters (FIRST) survey and employed the deep learning method. Among them, optical and/or infrared counterparts are identified for 41,425 FR-IIs. This catalog spans luminosities 2.63 × 1022 ≤ Lrad ≤ 6.76 × 1029 W Hz−1 and redshifts up to z = 5.01. The spectroscopic classification indicates that there are 1431 low-excitation radio galaxies and 260 high-excitation radio galaxies. Among the spectroscopically identified sources, black hole masses are estimated for 4837 FR-IIs, which are in 107.5 ≲ MBH ≲ 109.5M⊙. Interestingly, this catalog reveals a couple of giant radio galaxies (GRGs), which are already in the existing GRG catalog, confirming the efficiency of this FR-II catalog. Furthermore, 284 new GRGs are unveiled in this new FR-II sample; they have the largest projected sizes ranging from 701 to 1209 kpc and are located at redshifts 0.31 < z < 2.42. Finally, we explore the distribution of the jet position angle and it shows that the faint Images of the FIRST images are significantly affected by the systematic effect (the observing beams). The method presented in this work is expected to be applicable to the radio sky surveys that are currently being conducted because they have finely refined telescope arrays. On the other hand, we are expecting that further new methods will be dedicated to solving this problem.
分类： 天文学 >> 天文学 提交时间： 2024-03-29 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： Radiation pattern captures the electromagnetic performance of reflector antennas, which is significantly affected by the deformation of the primary reflector due to gravity and the displacement of the secondary reflector. During the design process of large reflector antennas, a substantial amount of time is often dedicated to iteratively adjusting structural parameters and validating electromagnetic performance. To improve the efficiency of the design process, we first propose an approximate calculation method of optical path difference (OPD) for the deformation of the primary reflector under gravity and the displacement of the secondary reflector. Then an OPD fitting function based on the modified Zernike polynomials is proposed to capture the phase difference of radiation over the aperture plane, based on which the radiation pattern will be obtained quickly by the aperture field integration method. Numerical experiments demonstrate the effectiveness of the proposed quick calculation method for analyzing the radiation pattern of a 10.4 m submillimeter telescope antenna at its highest operating frequency of 856 GHz. In comparison with the numerical simulation method based on GRASP (which is an antenna electromagnetic analysis tool combining physical optics (PO) and physical theory of diffraction (PTD)), the quick calculation method reduces the time for radiation pattern analysis from more than one hour to less than two minutes. Furthermore, the quick calculation method exhibits excellent accuracy for the figure of merit (FOM) of the radiation pattern. Therefore, the proposed quick calculation method can obtain the radiation pattern with high speed and accuracy. Compared to the time-consuming numerical simulation method (PO and PTD), it can be employed for quick analysis of the radiation pattern for the lateral displacement of the secondary reflector and the deformation of the primary reflector under gravity in the design process of a reflector antenna.
分类： 天文学 >> 天文学 提交时间： 2024-03-29 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： In today's society, there is a wide demand for high-precision and high-stability time service in the fields of electric power, communication, transportation and finance. At present, the time standard in various countries is mainly based on atomic clocks, but the frequency drift of atomic clocks will affect the long-term stability performance. Compared with atomic clocks, millisecond pulsars have better long-term stability and can complement with the excellent short-term stability of atomic clocks. In order to improve the long-term stability of the atomic timescale, and then improve the timing accuracy, this paper proposes an algorithm for steering the atomic clock ensemble (ACE) by ensemble pulsar time (EPT) based on digital phase locked loop (DPLL). First, the ACE and EPT are generated by the ALGOS algorithm, then the ACE is steered by EPT based on DPLL to calibrate the long-term frequency drift of the atomic clock, so that the generated steered atomic time follows both the short-term stability characteristics of ACE and the long-term stability characteristics of EPT, and finally, the steered atomic time is used to calibrate the local cesium clock. The experimental results show that the long-term stability of atomic time after steering is improved by 2 orders of magnitude compared with that before steering, and the daily drift of a local cesium clock after calibration is less than 9.47 ns in 3 yr, 3 orders of magnitude higher than that before calibration on accuracy.
分类： 天文学 >> 天文学 提交时间： 2024-03-29 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： The 2.5 m wide-field and high-resolution solar telescope (WeHoST) is currently under developing for solar observations. WeHoST aims to achieve high-resolution observations over a super-wide field of view (FOV) of 5' × 5', and a desired resolution of 0.3''. To meet the scientific requirements of WeHoST, the ground-layer adaptive optics (GLAO) with a specially designed wave front sensing system is as the primary consideration. We introduce the GLAO configuration, particularly the wave front sensing scheme. Utilizing analytic method, we simulate the performance of both classical AO and GLAO systems, optimize the wave front sensing system, and evaluate GLAO performance in terms of PSF uniformity and correction improvement across whole FOV. The results indicate that, the classical AO will achieve diffraction-limited resolution; the suggested GLAO configuration will uniformly improve the seeing across the full 5' × 5' FOV, reducing the FWHM across the axis FOV to less than 0.3'' (λ ≥ 705 nm, r0 ≥ 11 cm), which is more than two times improvement. The specially designed wave front sensor schedule offers new potential for WeHoST's GLAO, particularly the multi-FOV GLAO and the flexibility to select the detected area. These capabilities will significantly enhance the scientific output of the telescope.
分类： 天文学 >> 天文学 提交时间： 2024-03-29 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： The development of spectroscopic survey telescopes like Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), Apache Point Observatory Galactic Evolution Experiment and Sloan Digital Sky Survey has opened up unprecedented opportunities for stellar classification. Specific types of stars, such as early-type emission-line stars and those with stellar winds, can be distinguished by the profiles of their spectral lines. In this paper, we introduce a method based on derivative spectroscopy (DS) designed to detect signals within complex backgrounds and provide a preliminary estimation of curve profiles. This method exhibits a unique advantage in identifying weak signals and unusual spectral line profiles when compared to other popular line detection methods. We validated our approach using synthesis spectra, demonstrating that DS can detect emission signals three times fainter than Gaussian fitting. Furthermore, we applied our method to 579,680 co-added spectra from LAMOST Medium-Resolution Spectroscopic Survey, identifying 16,629 spectra with emission peaks around the Hα line from 10,963 stars. These spectra were classified into three distinct morphological groups, resulting in nine subclasses as follows. (1) Emission peak above the pseudo-continuum line (single peak, double peaks, emission peak situated within an absorption line, P Cygni profile, Inverse P Cygni profile); (2) Emission peak below the pseudo-continuum line (sharp emission peak, double absorption peaks, emission peak shifted to one side of the absorption line); (3) Emission peak between the pseudo-continuum line.
分类： 天文学 >> 天文学 提交时间： 2024-03-29 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： Solar activities have a great impact on modern high-tech systems, such as human aerospace activities, satellite communication and navigation, deep space exploration, and related scientific research. Therefore, studying the long-term evolution trend of solar activity and accurately predicting the future solar cycles are highly anticipated. Based on the wavelet transform and empirical function fitting of the longest recorded data of the annual average relative sunspot number (ASN) series of 323 yr to date, this work decisively verifies the existence of the solar century cycles and confirms that its length is about 104.0 yr, and the magnitude has a slightly increasing trend on the timescale of several hundred years. Based on this long-term evolutionary trend, we predict solar cycles 25 and 26 by using phase similar prediction methods. As for solar cycle 25, its maximum ASN will be about 146.7 ± 33.40, obviously stronger than solar cycle 24. The peak year will occur approximately in 2024, and the period will be about 11 ± 1 yr. As for solar cycle 26, it will start around 2030, and reach its maximum between 2035 and 2036, with maximum ASN of about 133.0 ± 3.200, and period of about 10 yr.
分类： 天文学 >> 天文学 提交时间： 2024-03-29 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： Galaxy morphology classifications based on machine learning are a typical technique to handle enormous amounts of astronomical observation data, but the key challenge is how to provide enough training data for the machine learning models. Therefore this article proposes an image data augmentation method that combines few-shot learning and generative adversarial networks. The Galaxy10 DECaLs data set is selected for the experiments with consistency, variance, and augmentation effects being evaluated. Three popular networks, including AlexNet, VGG, and ResNet, are used as examples to study the effectiveness of different augmentation methods on galaxy morphology classifications. Experiment results show that the proposed method can generate galaxy images and can be used for expanding the classification model's training set. According to comparative studies, the best enhancement effect on model performance is obtained by generating a data set that is 0.5–1 time larger than the original data set. Meanwhile, different augmentation strategies have considerably varied effects on different types of galaxies. FSL-GAN achieved the best classification performance on the ResNet network for In-between Round Smooth Galaxies and Unbarred Loose Spiral Galaxies, with F1 Scores of 89.54% and 63.18%, respectively. Experimental comparison reveals that various data augmentation techniques have varied effects on different categories of galaxy morphology and machine learning models. Finally, the best augmentation strategies for each galaxy category are suggested.
分类： 天文学 >> 天文学 提交时间： 2024-03-29 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： Twenty-five typical massive white dwarfs (WDs) are selected and the proton decay reaction catalyzed by magnetic monopoles (MMs) for these WDs is discussed. A velocity-dependent correction factor strongly affects the cross-section. We find that a strong suppression controls the monopole catalysis of nucleon decay by the correction factor. The maximum number of MMs is captured and the luminosity can be 2.235 × 1021 and 1.7859 × 1032erg s−1 (e.g., for the O+Ne core mass WD J055631.17+130639.78). The luminosities of most massive WDs agree well with the observations at relatively low temperatures (e.g., T6 = 0.1), but can be three and two orders of magnitude higher than those of the observations for model (I) and (II) at relatively high temperatures (e.g., T6 = 10), respectively. The luminosities of model (I) are about one order of magnitude higher than those of model (II). Since we consider the effect of the number of MMs captured on the mass–radius relation and the suppression of the proton decay by the correction factor, the study by model (II) may be an improved estimation.
分类： 天文学 >> 天文学 提交时间： 2024-03-29 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： In gamma-ray burst prompt emission, there is still no consistent conclusion if the precursor and main burst share the same origin. In this paper, we try to study this issue based on the relationship between pulse width and energy of the precursor and main burst. We systematically search the light curve data observed by Swift/BAT and Fermi/GBM, and find 13 long bursts with well-structured precursors and main bursts. After fitting the precursor light curve of each different energy channel with the Norris function, we find that there is not only a power-law relationship between precursor width and energy, but also a power-law relationship between the ratio of the rising width to the decaying width and energy. By comparing the relationship between the precursors and the main burst pulses, we find that the distribution of the precursors and the relationship between the power-law indices are roughly the same as those of the main burst. In addition, it is found that the precursor width distribution as well as the upper limit of the pulse width ratio does not exceed 1 and both are asymmetric, which are also consistent with the main burst. These indicate that the precursor and the main burst are indistinguishable, and the precursor and the main burst may have the same physical origin.
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