Chemical Analysis Method for Magnesia and Magnesia-Alumina Refractories——Gravimetric-Molybdenum Blue Photometric Method for Determination of Silicon Dioxide Content

This standard specifies the gravimetric-molybdenum blue photometric method for determination of silicon dioxide content.

Summary study of data-driven photometric stereo methods

Background A photometric stereo method aims to recover the surface normal of a 3D object observed under varying light directions.It is an ill-defined problem because the general reflectance properties of the surface are unknown.Methods This paper reviews existing data-driven methods,with a focus on their technical insights into the photometric stereo problem.We divide these methods into two categories,per-pixel and all-pixel,according to how they process an image.We discuss the differences and relationships between these methods from the perspective of inputs,networks,and data,which are key factors in designing a deep learning approach.Results We demonstrate the performance of the models using a popular benchmark dataset.Conclusions Data-driven photometric stereo methods have shown that they possess a superior performance advantage over traditional methods.However,these methods suffer from various limitations,such as limited generalization capability.Finally,this study suggests directions for future research.

Study of photometric phase curve:assuming a cellinoid ellipsoid shape for asteroid(106)Dione

We carried out new photometric observations of asteroid （106） Dione at three apparitions （2004, 2012 and 2015） to understand its basic physical properties. Based on a new brightness model, new photometric observational data and published data of （106） Dione were analyzed to characterize the morphology of Dione＇s photometric phase curve. In this brightness model, a cellinoid ellipsoid shape and three-parameter （H, G1, G2） magnitude phase function system were involved. Such a model can not only solve the phase function system parameters of （106） Dione by considering an asymmetric shape of an asteroid, but also can be applied to more asteroids, especially those without enough photometric data to solve the convex shape. Using a Markov Chain Monte Carlo （MCMC） method, Dione＇s absolute magnitude of H = 7.66＋0.03-0.03 mag, and phase function parameters G1 = 0.682＋0.077-0.077 and G2 = 0.081＋0.042-0.042 were obtained. Simultaneously, Dione＇s simplistic shape, orientation of pole and rotation period were also determined preliminarily.

Two Novel Approaches for Photometric Redshift Estimation based on SDSS and 2MASS

We investigate two training-set methods; support vector machines （SVMs） and Kernel Regression （KR） for photometric redshift estimation with the data from the databases of Sloan Digital Sky Survey Data Release 5 and Two Micron All Sky Survey. We probe the performances of SVMs and KR for different input patterns. Our experiments show that with more parameters considered, the accuracy does not always increase, and only when appropriate parameters are chosen, the accuracy can improve. For different approaches, the best input pattern is different. With different parameters as input, the optimal bandwidth is dissimilar for KR. The rms errors of photometric redshifts based on SVM and KR methods are less than 0.03 and 0.02, respectively. Strengths and weaknesses of the two approaches are summarized. Compared to other methods of estimating photometric redshifts, they show their superiorities, especially KR, in terms of accuracy.

The SAGE photometric survey: technical description

To investigate a huge sample of data related to the Stellar Abundance and Galactic Evolution(SAGE) survey in more detail, we are performing a northern sky photometric survey named SAGES with the SAGE photometric system.This system consists of eight filters: Str?mgren-u, SAGE-v, SDSS g, r, i, DDO-51, Hαwideand Hαnarrow, including three Sloan broadband filters, three intermediateband filters, two narrow-band filters and one newly-designed narrow-band filter.SAGES covers～12 000 square degrees of the northern sky with δ >-5°, excluding the Galactic disk(|b| < 10°) and the sky area 12 h <RA <18 h.The photometric detection limit depth at signal-to-noise ratio 5σ can be as deep as V～20 mag.SAGES will produce a photometric catalog with uniform depth for～500 million stars with atmospheric parameters including effective temperature Teff, surface gravity log g and metallicity[Fe/H], as well as interstellar extinction to each individual target.In this work, we will briefly introduce the SAGE photometric system, the SAGE survey and a preliminary test field of the open cluster NGC 6791 and its surroundings.

Long-term photometric study of a faint W UMa binary in the direction of M31

We carry out a re-analysis of the photometric data in Rclc bands which were taken during the Nainital Microlensing Survey from 1998 to 2002 with the aim to detect gravitational microlensing events in the direction of M31. Here, we do photometric analysis of a faint W UMa binary CSS_JO04259.3＋410629 identified in the target field. The orbital period of this star is found to be 0.266402±0.000018 d. The photometric mass ratio, q, is found to be 0.28±0.01. The photometric light curves are investigated using the Wilson-Devinney （WD） code and absolute parameters are determined using empirical relations which provide masses and radii of the binary as M1 = 1.19±0.09M⊙, M2 = 0.33±0.02M⊙ and R1 = 1.02±0.04R⊙, R2 = 0.58±0.08Re respectively based on Rc band data. Quite similar values are found by analyzing/c band data. From the photometric light curve examination, the star is understood to be a low mass-ratio overcontact binary of A-subtype with a high fill-out factor of about 47%. The binary system is found to be located approximately at a distance of 2.64±0.03 kpc having a separation of 2.01 ±0.05 Re between the two components.

Photometric studies of two W UMa type variables in the field of distant open cluster NGC 6866

We present photometric analysis of the two W UMa type binaries identified in the field of distant open star cluster NGC 6866. Although these systems, namely ID487 and ID494, were reported by Joshi et al., a detailed study of these stars has not been carried out before. The orbital periods of these stars are found to be 0.415110±0.000001 day and 0.366709±0.000004 day, respectively. Based on the photometric and infrared colors, we find their respective spectral types to be K0 and K3. The photometric light vari- ations of both stars show the O＇Connell effect which can be explained by employing a dark spot on the secondary components. The V and I band light curves are analyzed using the Wilson-Devinney （WD） code and relations given by Gazeas which yield radii and masses for the binary components of star ID487 of R1 = 1.24 ± 0.01R,R2 = 1.11 4- 0.02Re, and M1 = 1.24 ± 0.02Me, M2 = 0.96 ±0.05Me and for star ID494 of R1 = 1.22 ± 0.02Re, R2 = 0.81 4- 0.01 Re, and M1 = 1.20 4- 0.06 Me, M2 = 0.47 4- 0.01 Me.

Photometric redshift estimation for quasars by integration of KNN and SVM

The massive photometric data collected from multiple large-scale sky surveys offer significant opportunities for measuring distances of celestial objects by photometric redshifts. However, catastrophic failure is an unsolved problem with a long history and it still exists in the current photometric redshift estimation approaches （such as the k-nearest neighbor （KNN） algorithm）. In this paper, we propose a novel two-stage approach by integration of KNN and support vector machine （SVM） methods together. In the first stage, we apply the KNN algorithm to photometric data and estimate their corresponding Zphot. Our analysis has found two dense regions with catastrophic failure, one in the range of Zphot E [0.3, 1.2] and the other in the range of Zphot E [1.2, 2.1]. In the second stage, we map the photometric input pattern of points falling into the two ranges from their original attribute space into a high dimensional feature space by using a Gaussian kernel function from an SVM. In the high dimensional feature space, many outliers resulting from catastrophic failure by simple Euclidean distance computation in KNN can be identified by a classification hyperplane of SVM and can be further corrected. Experimental results based on the Sloan Digital Sky Survey （SDSS） quasar data show that the two-stage fusion approach can significantly mitigate catastrophic failure and improve the estimation accuracy of photometric redshifts of quasars. The percents in different /△z/ ranges and root mean square （rms） error by the integrated method are 83.47%, 89.83%, 90.90% and 0.192, respectively, compared to the results by KNN （71.96%, 83.78%, 89.73% and 0.204）.

BV(RI )c photometric study of three variable PMS stars in the field of V733 Cephei

This paper reports results from the first long-term BV(RI)c photometric CCD observations of three variable pre-main-sequence stars collected during the period from February 2007 to January 2020. The investigated stars are located in the field of the PMS star V733 Cep within the Cepheus OB3 association. All stars from our study show rapid photometric variability in all-optical passbands. In this paper, we describe and discuss the photometric behavior of these stars and the possible reasons for their variability. In the light variation of two of the stars, we found periodicity.

Estimating Photometric Redshifts with Artificial Neural Networks and Multi-Parameters

We calculate photometric redshifts from the Sloan Digital Sky Survey Data Release 2 （SDSS DR2） Galaxy Sample using artificial neural networks （ANNs）. Different input sets based on various parameters （e.g. magnitude, color index, flux information） are explored. Mainly, parameters from broadband photometry are utilized and their performances in redshift prediction are compared. While any parameter may be easily incorporated in the input, our results indicate that using the dereddened magnitudes often produces more accurate photometric redshifts than using the Petrosian magnitudes or model magnitudes as input, but the model magnitudes are superior to the Petrosian magnitudes. Also, better performance resuits when more effective parameters are used in the training set. The method is tested on a sample of 79 346 galaxies from the SDSS DR2. When using 19 parameters based on the dereddened magnitudes, the rms error in redshift estimation is σz = 0.020184. The ANN is highly competitive tool compared to the traditional template-fitting methods when a large and representative training set is available.

太阳系外行星探测技术概述

自20世纪90年代首次发现太阳系外行星(以下简称系外行星)以来,系外行星探测技术取得了飞速发展。目前已探测到超过5500颗系外行星,其中包括类地行星、超级地球、气态巨行星及冰巨行星等多种类型。这些发现极大地拓展了人类对自身周围环境和宇宙的认知,为理解行星形成和演化提供了宝贵的观测依据,也为寻找宜居行星和地外生命提供了重要线索。通过介绍系外行星探测的多种核心技术,包括原理和应用特点,旨在对比和分析不同探测方法的技术特征。通过分析多种探测技术的优势和局限性,为行星探测研究提供了实践参考和发展趋势展望。

基于紫外荧光光导的增强型局部放电光电传感技术对比研究

本文从提升局部放电光电检测效率角度出发,采用Dy^(3+)和Ce^(3+)掺杂荧光玻璃作为前端耦合光导,提升了放电紫外光谱波段的检测效率,并通过荧光光导与单光子器件相配合的方式,实现了宽光谱、高灵敏度的局部放电光电探测。研究中,首先对两种荧光光导的激发光谱和荧光光谱特性进行了对比分析,计算了其与硅光电倍增管和光电倍增管的匹配效率,在此基础上对两种光导的光度衰减时间和荧光脉冲滞后时间进行了测定,最后通过局部放电的实测,对比分析了两种光导测试系统的灵敏度、线性度及其在放电统计特性上的差异。

氮中六氟化硫气体标准物质制备

采用称量法制备氮中六氟化硫气体标准物质。通过与摩尔分数相近的国家一级气体标准物质在相同实验条件下比较测量,从而确定制备的气体标准物质的量值。采用气相色谱仪-火焰光度检测器(FPD)对制备的标准物质进行均匀性、稳定性检验。由比较法定值、均匀性和稳定性引入的不确定度,计算合成氮中六氟化硫气体标准物质量值的相对标准不确定度和相对扩展不确定度。研制的3种浓度的氮中六氟化硫气体标准物质摩尔分数分别为10.0、99.96、1002μmol/mol,相对扩展不确定度为2%(k=2),均匀性和稳定性良好,有效期为12个月。

Real-time Abnormal Detection of GWAC Light Curve based on Wavelet Transform Combined with GRU-Attention

Nowadays, astronomy has entered the era of Time-Domain Astronomy, and the study of the time-varying light curves of various types of objects is of great significance in revealing the physical properties and evolutionary history of celestial bodies. The Ground-based Wide Angle Cameras telescope, on which this paper is based, has observed more than 10 million light curves, and the detection of anomalies in the light curves can be used to rapidly detect transient rare phenomena such as microgravity lensing events from the massive data. However, the traditional statistically based anomaly detection methods cannot realize the fast processing of massive data. In this paper, we propose a Discrete Wavelet(DW)-Gate Recurrent Unit-Attention(GRU-Attention) light curve warning model. Wavelet transform has good effect on data noise reduction processing and feature extraction, which can provide richer and more stable input features for a neural network, and the neural network can provide more flexible and powerful output model for wavelet transform. Comparison experiments show an average improvement of 61% compared to the previous pure long-short-term memory unit(LSTM) model, and an average improvement of 53.5% compared to the previous GRU model. The efficiency and accuracy of anomaly detection in previous paper work are not good enough, the method proposed in this paper possesses higher efficiency and accuracy,which incorporates the Attention mechanism to find out the key parts of the light curve that determine the anomalies. These parts are assigned higher weights, and in the actual anomaly detection, the star is detected with83.35% anomalies on average, and the DW-GRU-Attention model is compared with the DW-LSTM model, and the detection result f1 is improved by 5.75% on average, while having less training time, thus providing valuable information and guidance for astronomical observation and research.

The First Ground-based White Light Lunar Polarization Imaging:A New Kind of FeO Observation on the Near Side of the Moon

Lunar optical polarization is a fascinating phenomenon that occurs when sunlight reflects off the surface of the Moon and becomes polarized.This study employs a novel split-focus plane polarimetric camera to conduct the initial white light polarimetric observations on the near side of the Moon.We obtained the linear degree of polarization(DOP)parameters of white light by observation from the eastern and western hemispheres of the Moon.The findings indicate that the white light polarization is lower in the lunar highland than in the lunar maria overall.Combining the analysis of lunar soil samples,we noticed and determined that the DOP parameters of white light demonstrate high consistency with iron oxide on the Moon.This study may serve as a new diagnostic tool for the Moon.

Accelerating Asteroidal Period and Pole Inversion from Multiple Lightcurves Using Parallel Differential Evolution and Cellinoid Shape Model

Determining asteroid properties provides valuable physical insights but inverting them from photometric lightcurves remains computationally intensive.This paper presents a new approach that combines a simplified Cellinoid shape model with the Parallel Differential Evolution(PDE)algorithm to accelerate inversion.The PDE algorithm is more efficient than the Differential Evolution algorithm,achieving an extraordinary speedup of 37.983 with 64 workers on multicore CPUs.The PDE algorithm accurately derives period and pole values from simulated data.The analysis of real asteroid lightcurves validates the method’s reliability:in comparison with results published elsewhere,the PDE algorithm accurately recovers the rotational periods and,given adequate viewing geometries,closely matches the pole orientations.The PDE approach converges to solutions within 20,000 iterations and under one hour,demonstrating its potential for large-scale data analysis.This work provides a promising new tool for unveiling asteroid physical properties by overcoming key computational bottlenecks.

A Study of the Comets with Large Perihelion Distances C/2019 L3(ATLAS)and C/2019 O3(Palomar)

This work analyzes the photometric data of the Oort spike comets C/2019 L3(ATLAS)and C/2019 O3(Palomar)obtained between 2016 and 2023 by the ATLAS network and the Belgian Olmen Observatory.The comets Palomar and ATLAS have a typical and unusually high activity level,respectively,based on the Afρparameter corrected to phase angle zero at perihelion.The absolute magnitude of comets ATLAS and Palomar in the o-band is 4.71±0.05 and 4.16±0.02 respectively.The cometary activity of comets ATLAS and Palomar probably began at r>13 au before perihelion and will end at r>14 au after perihelion,which means that they could remain active until the second half of 2026.The nucleus of comet ATLAS has a minimum radius of 7.9 km,and the nucleus of comet Palomar could be a little larger.The c-o colors of the comets ATLAS and Palomar are redder and bluer,respectively,at perihelion than the solar twin YBP 1194.These comets showed a bluish trend in the coma color with decreasing heliocentric distance.Comet Palomar probably had two outbursts after its perihelion,each releasing about 10^(8)kg of dust.The slopes of the photometric profile of the comae of these comets were between 1and 1.5,indicating a steady state during the observation campaign.

基于光度滴定法研制的COD_(Mn)在线分析仪

基于光度滴定法研制了一种高锰酸盐指数在线分析仪,介绍了分析仪的分析流路,滴定反应装置,并对滴定终点判定方法进行了优化,同时对分析仪的性能进行了测定。研究结果表明:在0~20mg/L的量程范围内,分析仪的标准曲线的R^(2)值为0.9999;定量下限为0.29mg/L;重复性误差为0.42%,零点漂移与量程漂移分别为0.31%与0.35%,葡萄糖试验为0.61%,实际水样比对试验为6.92%。本分析仪方法灵敏度高,准确度高,精密度好,定量下限低,适于现场水质监测。

Inhomogeneity in Spectral Transmission of the Coated UB VRI Filters of BFOSC and its Influence on Photometry

In order to realize the Johnson UBV and Kron-Cousins RI photometric systems in BFOSC, glass filters were purchased according to the Bessell prescription. All the filters are anti-reflection coated,on both sides to increase the transmission. By comparing two dome flat-field exposures taken through any one of these filters set in two orientations 90degrees apart, inhomogeneities in the filter transmission is clearly demonstrated. Using a PDS microphotometer, we have confirmed that the form of their spectral transmission curve varied from point to point on the filters. This kind of inhomogeneity cannot be eliminated by dividing by flat-fielding exposure and must be ascribed to inhomogeneities in the coating. This is not some accidental defect in coating, it is in the existing coating technique because all the filters (including the narrow-band interference ones) for the BFOSC and a Hbeta filter made by another manufacturer showed a similar pattern. We found that for the studies of variable stars with amplitudes less than 0.05 mag. or studies aiming at establishing accurate C-M diagrams of star clusters, the usual uncoated Schott glass filters of Bessell's prescription are to be preferred.

BGLS-based method of estimating the rotational periods of asteroids

As the asteroid rotational period is important to the study of the properties of asteroids(e.g.,super-fast rotators have structures owing an internal cohesion(rather than being rubble piles bounded by gravity only) so as not to fly apart), constructing an effective and fast method used to search the period attracts much researchers' attention. Recently, the Bayesian generalized Lomb–Scargle(BGLS)periodogram was developed to improve the convergence efficiency of the Lomb–Scargle method. However,the result of BGLS varies with the frequency range and cannot meet the two minimum/maximum requirements for a complete rotation of the asteroid. We propose a robust BGLS-based method that efficiently determines rotational periods. The proposed method employs a polynomial series to fit folded light curves with potential periods, initially calculated using the BGLS periodogram, and adopts a merit function to estimate and refine best-fit periods. We estimate the rotational periods of 30 asteroids applying the new method to light curves from the Palomar Transient Factory. Results confirm the effectiveness of the BGLS-based method in deriving rotational periods from ground-based observations of asteroids. Further application of the BGLS-based method to sparse light curves, such as Gaia data, is discussed.