Publications by authors named "Ali Luo"

Copper (Cu)-based catalysts have established their unique capability for yielding wide value-added products from CO. Herein, we demonstrate that the pathways of the electrocatalytic CO reduction reaction (CORR) can be rationally altered toward C or C products by simply optimizing the coordination of Cu with O-containing organic species (squaric acid (HCO) and cyclohexanehexaone (CO)). It is revealed that the strength of Cu-O bonds can significantly affect the morphologies and electronic structures of derived Cu catalysts, resulting in the distinct behaviors during CORR.

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The unexpected discovery of hot Jupiters challenged the classical theory of planet formation inspired by our solar system. Until now, the origin and evolution of hot Jupiters are still uncertain. Determining their age distribution and temporal evolution can provide more clues into the mechanism of their formation and subsequent evolution.

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In astronomical spectral analysis, class recognition is essential and fundamental for subsequent scientific research. The experts often perform the visual inspection after automatic classification to deal with low-quality spectra to improve accuracy. However, given the enormous spectral volume and inadequacy of the current inspection practice, such inspection is tedious and time-consuming.

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The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), also known as the Guoshoujing Telescope, is a major national scientific facility for astronomical research located in Xinglong, China. Beginning with a pilot survey in 2011, LAMOST has been surveying the night sky for more than 10 years. The LAMOST survey covers various objects in the Universe, from normal stars to peculiar ones, from the Milky Way to other galaxies, and from stellar black holes and their companions to quasars that ignite ancient galaxies.

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Exposure to cigarette smoke (CS) pollution has previously associated with dry eye symptoms but without detailed experimental data and elucidation of the mechanism. We aimed to evaluate the effects of CS on the ocular surfaces of mice and the extraction of DMSO lipid-soluble cigarette smoke particles (DCSP) on cultured human corneal epithelial cells (HCECs), and explore to elucidate the probable mechanism. C57BL mice were exposed to CS challenging.

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Objective: To investigate the expression of amyloid precursor protein (APP) and amyloid beta (Aβ) in cornea and further explore the pathological and ultrastructural changes in corneal epithelium in APPswePS1 transgenic mice.

Methods: Twelve wild type mice were grouped into control group and twelve TgAPPswePS1 mice at least 8 months old were grouped into the young experiment group (Tg-8M group), and another twelve transgenic mice at least 15 months old were selected into the aged experiment group (Tg-15M group). The pathological degeneration, ultrastructural changes, and the expression of APP, Aβ deposition, and the TUNEL reaction in corneal epithelial cells were observed.

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We discover a population of short-period, Neptune-size planets sharing key similarities with hot Jupiters: both populations are preferentially hosted by metal-rich stars, and both are preferentially found in systems with single-transiting planets. We use accurate Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Data Release 4 (DR4) stellar parameters for main-sequence stars to study the distributions of short-period [Formula: see text] planets as a function of host star metallicity. The radius distribution of planets around metal-rich stars is more "puffed up" compared with that around metal-poor hosts.

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The nearly circular (mean eccentricity [Formula: see text]) and coplanar (mean mutual inclination [Formula: see text]) orbits of the solar system planets motivated Kant and Laplace to hypothesize that planets are formed in disks, which has developed into the widely accepted theory of planet formation. The first several hundred extrasolar planets (mostly Jovian) discovered using the radial velocity (RV) technique are commonly on eccentric orbits ([Formula: see text]). This raises a fundamental question: Are the solar system and its formation special? The Kepler mission has found thousands of transiting planets dominated by sub-Neptunes, but most of their orbital eccentricities remain unknown.

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Article Synopsis
  • The analysis of celestial spectra reveals important astrophysical information about celestial bodies, including their physical attributes, chemical makeup, and atmospheric conditions.
  • Large surveys like LAMOST and SDSS generate extensive spectral data, necessitating advanced processing techniques to classify massive amounts of stellar spectra efficiently.
  • This paper explores the use of Bayes' theorem alongside Lick indices to categorize stellar spectra into three types (F, G, K) and leverages Hadoop for parallel computation, enhancing processing speed and efficiency.
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LAMOST-DR1 is the first data released by Guoshoujing telescop, which has the largest number of stellar spectra in the world at present. The data set provides the data source for searching for special and rare celestial objects like cataclysmic variable stars.Meanwhile, it requires more advanced astronomical data processing methods and techniques.

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The redshift measurement of galaxy spectrum is a key issue in large astronomical spectral survey. Its goal is to extract the redshift from spectrum, which is caused the Doppler Effect. With the development of the extragalactic sky survey project, the distance (redshift) of the observed targets is becoming further.

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We have collected massive stellar spectral data in recent years, which leads to the research on the automatic measurement of stellar atmospheric physical parameters (effective temperature Teff, surface gravity log g and metallic abundance [Fe/ H]) become an important issue. To study the automatic measurement of these three parameters has important significance for some scientific problems, such as the evolution of the universe and so on. But the research of this problem is not very widely, some of the current methods are not able to estimate the values of the stellar atmospheric physical parameters completely and accurately.

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Article Synopsis
  • Distance metrics are crucial for analyzing spectroscopic survey data, as they help measure the distance between different spectra, aiding in classification, clustering, and outlier detection.
  • A new method called Residual Distribution Distance is introduced, which scales spectra to the same level and calculates the distance based on the standard deviation of residuals, improving accuracy over traditional methods.
  • This approach is demonstrated through stellar subcategory classification, showing that it more effectively distinguishes between types of spectra and is also evaluated for performance with varying signal-to-noise ratios (SNR).
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This paper presents a method to estimate stellar metallicity based on BP neural network and Ca line index. This method trains a BP ANN model from SDSS/SEGUE stellar spectra and parameters provided by SSPP. The values of Teff and the line index of Ca lines are the input of network while the [Fe/H] values are the oputput of the network.

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Background: Liver fibrosis is a feature in the majority of chronic liver diseases and oxidative stress is considered to be its main pathogenic mechanism. Antioxidants including vitamin E, are effective in preventing liver fibrogenesis. Several plant-drived antioxidants, such as silymarin, baicalin, beicalein, quercetin, apigenin, were shown to interfere with liver fibrogenesis.

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In the present paper, a local mean-based K-nearest centroid neighbor (LMKNCN) technique is used for the classification of stars, galaxies and quasars (QSOS). The main idea of LMKNCN is that it depends on the principle of the nearest centroid neighborhood(NCN), and selects K centroid neighbors of each class as training samples and then classifies a query pattern into the class with the distance of the local centroid mean vector to the samples . In this paper, KNN, KNCN and LMKNCN were experimentally compared with these three different kinds of spectra data which are from the United States SDSS-DR8.

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The focal ratio degradation (FRD) of optical fiber is one of major sources causing light loss in multi-fiber astronomical instruments. Meanwhile, the sky subtraction is crucial to multi-fiber spectra reduction, especially for the objects which are as faint as the sky background, not to mention for those even fainter ones. To improve the accuracy of sky subtraction, it is necessary to normalize the throughput among object fibers and sky sampling fibers.

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There are many valuable rare and unusual objects in spectra dataset of Sloan Digital Sky Survey (SDSS) Data Release eight (DR8), such as special white dwarfs (DZ, DQ, DC), carbon stars, white dwarf main-sequence binaries (WDMS), cataclysmic variable (CV) stars and so on, so it is extremely significant to search for rare and unusual celestial objects from massive spectra dataset. A novel algorithm based on Kernel dense estimation and K-nearest neighborhoods (KNN) has been presented, and applied to search for rare and unusual celestial objects from 546 383 stellar spectra of SDSS DR8. Their densities are estimated using Gaussian kernel density estimation, the top 5 000 spectra in descend order by their densities are selected as rare objects, and the top 300 000 spectra in ascend order by their densities are selected as normal objects.

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Supernova (SN) is called the "standard candles" in the cosmology, the probability of outbreak in the galaxy is very low and is a kind of special, rare astronomical objects. Only in a large number of galaxies, we have a chance to find the supernova. The supernova which is in the midst of explosion will illuminate the entire galaxy, so the spectra of galaxies we obtained have obvious features of supernova.

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At present, most sky-subtraction methods focus on the full spectrum, not the particular location, especially for the backgroud sky around [OIII] line which is very important to low redshift quasars. A new method to precisely subtract sky lines in local region is proposed in the present paper, which sloves the problem that the width of Hβ-[OIII] line is effected by the backgroud sky subtraction. The exprimental results show that, for different redshift quasars, the spectral quality has been significantly improved using our method relative to the original batch program by LAMOST.

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The radial velocity of the star is very important for the study of the dynamics structure and chemistry evolution of the Milky Way, is also an useful tool for looking for variable or special objects. In the present work, we focus on calculating the radial velocity of different spectral types of low-resolution stellar spectra by adopting a template matching method, so as to provide effective and reliable reference to the different aspects of scientific research We choose high signal-to-noise ratio (SNR) spectra of different spectral type stellar from the Sloan Digital Sky Survey (SDSS), and add different noise to simulate the stellar spectra with different SNR. Then we obtain theradial velocity measurement accuracy of different spectral type stellar spectra at different SNR by employing a template matching method.

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As the most common stars in the galaxy, M dwarfs can be used to trace the structure and evolution of the Milky Way. Besides, investigating M dwarfs is important for searching for habitability of extrasolar planets orbiting M dwarfs. Spectral classification of M dwarfs is a fundamental work.

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Using the Lick line index, according to the magnanimity characteristics of the spectrum an efficient algorithm of the atmospheric physical parameters measurement by the linear regression method from the point of view of statistical regression was designed. The linear regression was used to achieve the best regression effect by selecting the type of regression and the composition of line index. The formula obtained from the regression model makes the computation speed fast when applied to new data, and the clarity and ease of analysis processing can not be reached by other methods.

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Template matching is one of the most commonly used methods of automatic stellar spectrum parameter measurement The present paper made comparisons among the three commonly used template matching methods K-Nearest Neighbor (KNN), the Chi-square minimization and cross correlation method. The Continuum normalization and flux normalization were made first. Then the three mentioned methods were compared in measurement results of stellar spectrum parameters.

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In stellar spectral processing, template matching method can be used to obtain comparably ideal results of stellar spectrum parameters by using pattern recognition algorithms, without computing the spectral line-index. The present paper proposed a similarity based method to measure stellar spectrum parameters automatically. First, the continuum normalization was made, and then the similarities between the stellar spectrum and the template spectrum were compared to get more accurate stellar spectrum parameters.

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