The dynamical mass of a classical Cepheid variable star in an eclipsing binary system

Stellar pulsation theory provides a means of determining the masses of pulsating classical Cepheid supergiants-it is the pulsation that causes their luminosity to vary. Such pulsational masses are found to be smaller than the masses derived from stellar evolution theory: this is the Cepheid mass discrepancy problem, for which a solution is missing. An independent, accurate dynamical mass determination for a classical Cepheid variable star (as opposed to type-II Cepheids, low-mass stars with a very different evolutionary history) in a binary system is needed in order to determine which is correct. The accuracy of previous efforts to establish a dynamical Cepheid mass from Galactic single-lined non-eclipsing binaries was typically about 15-30% (refs 6, 7), which is not good enough to resolve the mass discrepancy problem. In spite of many observational efforts, no firm detection of a classical Cepheid in an eclipsing double-lined binary has hitherto been reported. Here we report the discovery of a classical Cepheid in a well detached, double-lined eclipsing binary in the Large Magellanic Cloud. We determine the mass to a precision of 1% and show that it agrees with its pulsation mass, providing strong evidence that pulsation theory correctly and precisely predicts the masses of classical Cepheids.     

一种基于虚构数据区多重校验的数据库入侵检测模型

当前的大型数据库中,广泛存在着抗干扰性差,主要是由于检测数据量的巨大使得传统的算法陷入了局部搜索效率低的缺陷当中,造成对潜在风险检测效果不明显等弊端。提出了一种基于虚构数据区域多重校验的数据库入侵检测模型。通过运用数据的相似风险属性组成一个虚拟的小型风险区域,运用多重校验的方法,计算区域中风险最大的数据属性。通过细化虚拟区域,避免传统穷举算法中存在搜索能力不强的缺陷。对潜在的数据入侵风险进行有效的检测。实验表明,该算法提高了一些大型网络数据库入侵检测的准确率,取得了不错的效果。     

信号检测通道特性标定方法的研究

在控制系统中,经常需要对模拟量系统前向通道的特性进行标定.传统的手工标定方法测试时间长、准确度低及效率低下;而具有强大数据处理功能的微机不仅可以完成对标定测试数据自动、高速的处理,还能够提供操作人员一个良好的人机交互界面,控制整个标定的过程.文章阐述了采用最大似然估计的参数估计思想获得信号检测通道特性参数的原理,并提出了两种基于最小二乘法的标定测试数据处理方法.经实践检验,该方法简便易行,并能满足精度要求.     

Direct detection of a magnetic field in the innermost regions of an accretion disk

Models predict that magnetic fields play a crucial role in the physics of astrophysical accretion disks and their associated winds and jets. For example, the rotation of the disk twists around the rotation axis the initially vertical magnetic field, which responds by slowing down the plasma in the disk and by causing it to fall towards the central star. The magnetic energy flux produced in this process points away from the disk, pushing the surface plasma outwards, leading to a wind from the disk and sometimes a collimated jet. But these predictions have hitherto not been supported by observations. Here we report the direct detection of the magnetic field in the core of the protostellar accretion disk FU Orionis. The surface field reaches strengths of about 1 kG close to the centre of the disk, and it includes a significant azimuthal component, in good agreement with recent models. But we find that the field is very filamentary and slows down the disk plasma much more than models predict, which may explain why FU Ori fails to collimate its wind into a jet.     

阿特拉津降解细菌的直接检测及分离

摘要：利用改良的 SM固体培养基,对受除草剂污染的土壤中阿特拉津降解菌进行了检测、计数及分离。研究发现,在工业污染土壤中,阿特拉津降解菌群成为微生物群落的主要组成部分,而在农业土壤中仅占次要地位。用多重PCR分析了靶向基因trzN 和 atzABC,表明含trzN-atzBC基因组合的降解菌在山东省工业及农业土壤中占主导地位。因为富集偏差的消除,直接分离方法更利于阿特拉津降解菌多样性分析的研究。     

A dynamical calibration of the mass-luminosity relation at very low stellar masses and young ages

Mass is the most fundamental parameter of a star, yet it is also one of the most difficult to measure directly. In general, astronomers estimate stellar masses by determining the luminosity and using the 'mass-luminosity' relationship, but this relationship has never been accurately calibrated for young, low-mass stars and brown dwarfs. Masses for these low-mass objects are therefore constrained only by theoretical models. A new high-contrast adaptive optics camera enabled the discovery of a young (50 million years) companion only 0.156 arcseconds (2.3 au) from the more luminous (> 120 times brighter) star AB Doradus A. Here we report a dynamical determination of the mass of the newly resolved low-mass companion AB Dor C, whose mass is 0.090 +/- 0.005 solar masses. Given its measured 1-2-micrometre luminosity, we have found that the standard mass-luminosity relations overestimate the near-infrared luminosity of such objects by about a factor of approximately 2.5 at young ages. The young, cool objects hitherto thought to be substellar in mass are therefore about twice as massive, which means that the frequency of brown dwarfs and planetary mass objects in young stellar clusters has been overestimated.     

Direct detection of a microlens in the Milky Way.

The nature of dark matter remains mysterious, with luminous material accounting for at most approximately 25 per cent of the baryons in the Universe. We accordingly undertook a survey looking for the microlensing of stars in the Large Magellanic Cloud (LMC) to determine the fraction of Galactic dark matter contained in massive compact halo objects (MACHOs). The presence of the dark matter would be revealed by gravitational lensing of the light from an LMC star as the foreground dark matter moves across the line of sight. The duration of the lensing event is the key observable parameter, but gives non-unique solutions when attempting to estimate the mass, distance and transverse velocity of the lens. The survey results to date indicate that between 8 and 50 per cent of the baryonic mass of the Galactic halo is in the form of MACHOs (ref. 3), but removing the degeneracy by identifying a lensing object would tighten the constraints on the mass in MACHOs. Here we report a direct image of a microlens, revealing it to be a nearby low-mass star in the disk of the Milky Way. This is consistent with the expected frequency of nearby stars acting as lenses, and demonstrates a direct determination of a lens mass from a microlensing event. Complete solutions such as this for halo microlensing events will probe directly the nature of the MACHOs.     

单相平衡体系热力学特征变量和独立自变量关系的探讨

在确定平衡体系状态的独立自变量基础上，讨论了单相平衡体系热力学特征变量与独立自变量的关系，并说明多相平衡体系只有描述体系平衡状态的独立自变量，而无特征变量．     

一种关节式坐标测量机的建模及其标定

为了研究7轴关节式坐标测量机的测量模型及其标定技术,根据DH模型(Denavit-Hartenberg notation)对7轴关节式坐标测量机进行了建模,并对参数个数和含义进行了深入研究.通过仿真发现7轴关节式坐标测量机直接标定时不能有效辨识某些参数的特殊问题.为解决该问题,设计了弯杆测头对测量机的整机参数进行标定.最后,将测量机测头换回直杆测头进行测头校准,获得更换测头后的测头参数.实验表明该方法能够有效地辨识出测量机整机的参数,能有效保证测量机的精度,这也证明了给出的测量模型的正确性.     

仿真型索星卡软件的设计与实现

设计并实现了一种用户界面与经典的TS系列索星卡高度近似的仿真型索星卡软件.该软件对实体索星卡的星体数据恒定及网片纬度离散化等固有局限进行改进,可实时计算星体的高度方位并支持自动确定星空以大幅降低用户操作的复杂度,同时为用户提供了可见星体列表等多种丰富实用的功能.     

霍奇星算子与外微分算符的组合规律

系统探讨了霍奇星算子与外微分算符作用于任意微分形式场时二者的一般组合规律.首先,找到了保持微分形式场的次不变的2个组合算符,并通过二者的线性组合得到了一个新算符.其次,当由任意数目的霍奇星算子与外微分算符进行组合时,导出了所有形式上彼此互异的组合算符的统一表达式.这些表达式由单个霍奇星算子与外微分算符以及二者的任选2个的非零组合构成.在此基础上,分析了所有算符之间的相互作用关系,并根据这些算符对微分形式的次的改变情况,对它们进行了具体分类.最后,作为一个应用,详细讨论了如何由次相同的微分形式的线性组合来构造电磁场的麦克斯韦方程.     

几种摄像机标定方法的比较

本文针对摄像机参数标定进行了研究.借助于标定模板,用三种方法予以实现.其一,人工标定;其二,借助于OpenCV的标定,该方法自动确定参照模板上的角点及其坐标值来计算摄像机的参数,提高了精度;其三,基于张正友软件的标定.相较于人工及张正友的标定,基于OpenCV的标定方便、快捷,达到了较好的实用性.     

独立集上最小最大比值和最小极差比值问题的算法

定义在集Ｅ的子集Ｘ上的两个实函数的比值的极大、极小值分别记为Ｍ（Ｘ）和ｍ（Ｘ），极差△（Ｘ）＝Ｍ（Ｘ）－ｍ（Ｘ）。本文给出在秩为ｒ的独立系统（Ｅ，Ｉ）（ＩＰ（Ｅ））中求ｍａｘ｛ｍ（Ｘ）｜Ｘ∈Ｉ｜，｜Ｘ｜＝ｒ｝和ｍｉｎ｛△（Ｘ）｜Ｘ∈Ｉ｜，｜Ｘ｜＝ｒ｝的有效算法及其证明。     

Direct and selective binding of an acidic transcriptional activation domain to the TATA-box factor TFIID

The potent transactivation domain of the herpes simplex virion protein VP16 was used as a column ligand for affinity chromatography. VP16 binds strongly and highly selectively to the human and yeast TATA box-binding factors. Our results imply that the principal target for acidic activation domains is the TATA-box factor TFIID.     

Direct observation of the discrete character of intrinsic localized modes in an antiferromagnet

In a strongly nonlinear discrete system, the spatial size of an excitation can become comparable to, and influenced by, the lattice spacing. Such intrinsic localized modes (ILMs)--also called 'discrete breathers' or 'lattice solitons'--are responsible for energy localization in the dynamics of discrete nonlinear lattices. Their energy profiles resemble those of localized modes of defects in a harmonic lattice but, like solitons, they can move (although, unlike solitons, some energy is exchanged during collisions between them). The manipulation of these localized energy 'hotspots' has been achieved in systems as diverse as annular arrays of coupled Josephson junctions, optical waveguide arrays, two-dimensional nonlinear photonic crystals and micromechanical cantilever arrays. There is also some evidence for the existence of localized excitations in atomic lattices, although individual ILMs have yet to be identified. Here we report the observation of countable localized excitations in an antiferromagnetic spin lattice by means of a nonlinear spectroscopic technique. This detection capability permits the properties of individual ILMs to be probed; the disappearance of each ILM registers as a step in the time-dependent signal, with the surprising result that the energy staircase of ILM excitations is uniquely defined.     

CS-ISPH-TPP亚微米颗粒的粒径与表面电位影响因素研究

以带正电的几丁聚醣(CS)与带负电的三聚磷酸钠(TPP)通过离子交联作用包覆分离大豆蛋白质水解物(ISPH)制成CS-ISPH-TPP亚微米颗粒,利用动态光散射法分析ISPH浓度、CS分子量及CS/TPP质量比对亚微米颗粒的粒径与表面电位的影响。结果表明,CSISPH-TPP亚微米颗粒的粒径随ISPH添加浓度的增加而增大,而表面电位则无明显变化。CSTPP与CS-ISPH-TPP亚微米颗粒的粒径会随CS分子量的增加而增大,且包覆ISPH颗粒的粒径均大于未包覆的颗粒,而表面电位则介于41.9~44.2 m V之间。CS/TPP质量比由6∶1减至4∶1时,颗粒粒径会随之增加,而由4∶1减至2∶1时,粒径则变小;CS/TPP质量比由6∶1减至3∶1时,颗粒表面均带有高度的正电荷,继续减至2∶1时,表面电位会出现骤降的情形。     

矩阵的B-H序和*序

讨论矩阵的B-H序、 *序和左(右)*序之间的关系. 对于部分等距矩阵, 证明了它们之间是一致的.