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1. chinaXiv:202005.00040 [pdf]

全日面磁场与活动监测望远镜轴系升级

陈垂裕; 郭晶晶; 林佳本; 邓元勇
Subjects: Astronomy >> Astrophysical processes

在天文观测中,需要望远镜能快速、准确的指向目标天体(如太阳等),并对其进行稳定跟踪。本文针对怀柔太阳观测基地(HSOS)的全日面磁场与活动监测望远镜(SMAT)进行轴系升级,使用伺服电机轴上23位高精度绝对式编码器替代光栅钢带码盘;通过VSOP87行星理论实时计算日面中心位置,使用基于大面阵CCD的高精度导行系统不间断跟踪太阳并记录太阳位置,利用最小二乘法分段拟合太阳实时位置与绝对值编码器数值,建立起指向算法并实现日面中心指向。经实测,赤经方向的指向误差约为36.69″,赤纬方向的指向误差约为21.49″,满足SMAT的指向要求,该方法成本低兼容性高,对于其他赤道式望远镜的升级改造具有借鉴意义。

submitted time 2020-05-12 From cooperative journals:《天文研究与技术》 Hits247Downloads138 Comment 0

2. chinaXiv:202005.00041 [pdf]

K波段常温接收机噪声注入定标方法分析研究

王凯; 闫浩; 段雪峰; 马军; 陈卯蒸; 王洋; 曹亮; 陈晨雨; 李鹏
Subjects: Astronomy >> Astrophysical processes

噪声注入定标方法作为厘米波段一种常规强度校准方式而被广泛使用。通过组建K波段常温接收机及其定标平台,在室内20℃下使用传统冷热负载法标定接收机噪声温度及噪声源温度,之后在室外-7℃中使用同样方法再次标定上述参数,并利用室内标定的噪声源去进一步标定室外环境中接收机的噪声温度。测试结果表明,在环境温度变化约27度时,接收机噪声温度定标差异约为50.5%,标准噪声源定标差异约为41%。故此得知,如若将噪声注入法应用于常温接收机定标中,首先需考虑对接收机进行恒温处理,另外可采取对注入的标准噪声源进行温度补偿,使其可以更加精确的应用于二次定标当中,这也是本论文下一步计划开展的工作。

submitted time 2020-05-12 From cooperative journals:《天文研究与技术》 Hits227Downloads130 Comment 0

3. chinaXiv:202005.00042 [pdf]

5BZCAT BZUs的分类

朱惊天; 樊军辉; 蔡金庭
Subjects: Astronomy >> Astrophysical processes

本文用4种机器学习方法:支持向量机(SVM)、随机森林(RF)、集成学习(EM)和多层感知机(MLP),将5BZCAT中227个BZUs分为BL Lacs候选体和FSRQs候选体,并通过特征工程和网格搜索方法提高分类准确率。综合4种分类器的分类结果,本文中,将判别概率阈值设为0.8,得到33个BL Lacs候选体和119个FSRQs候选体。

submitted time 2020-05-12 From cooperative journals:《天文研究与技术》 Hits337Downloads254 Comment 0

4. chinaXiv:202005.00039 [pdf]

心理与教育测验中异常反应侦查新技术:变点分析法 (CPA)

张龙飞; 王晓雯; 蔡艳; 涂冬波
Subjects: Psychology >> Psychological Measurement

变点分析法(change point analysis, CPA)近些年才引入心理与教育测量学,相较于传统方法,CPA不仅可以侦查异常作答被试,还能自动精确地定位变点位置,高效清洗作答数据。其原理在于:判断作答序列中是否存在可将该序列划分为具有不同统计学属性两部分的点(即变点),并且需使用被试拟合统计量(person-fit statistic, PFS)来量化两个子序列之间的差异。未来可将单变点分析拓展至多变点,结合反应时等信息,构建非参数化指标以及将现有指标拓展至多级计分或多维测验,以提高CPA的适用广度及效力。

submitted time 2020-05-12 Hits1002Downloads849 Comment 0

5. chinaXiv:201607.00046 [pdf]

Exact Solution for Three-Dimensional Ising Model

Zhang, Degang
Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

Three-dimensional Ising model in zero external field is exactly solved by operator algebras, similar to the Onsager's approach in two dimensions. The partition function of the simple cubic crystal imposed by the periodic boundary condition along both $(0 1 0)$ and $(0 0 1)$ directions and the screw boundary condition along the $(1 0 0)$ direction is calculated rigorously. In the thermodynamic limit an integral replaces a sum in the formula of the partition function. A order-disorder transition in the infinite crystal occurs at a temperature $T=T_c$ determined by the condition: $\sinh\frac{2J}{k_BT_c}\sinh\frac{2(J_1+J_2)}{k_BT_c}=1$, where $(J_1 J_2 J)$ are the interaction energies in three directions, respectively. The analytical expressions for the internal energy and the specific heat are also given. It is also shown that the thermodynamic properties of 3D Ising model with $J_1=J_2$ are connected to those in 2D Ising model with the interaction energies $(J_1 J_{2D})$ by the relation $(\frac{J_{2D}}{k_BT})^*=(\frac{J}{k_BT})^*-\frac{J_1}{k_BT}$, where $x^*=\frac{1}{2}{\rm ln coth} x={\rm tanh}^{-1}(e^{-2x})$.

submitted time 2020-05-12 Hits14266Downloads1707 Comment 0

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