首次发现银河系外行星

正一项于2018年2月2日发表在The AstrophysicalJournal上的研究表明,科学家们首次发现了银河系外的一群行星。为了探测到该群行星,来自美国俄克拉荷马大学的天体物理学小组利用了微引力透镜(microlensing)——目前已知的唯一能有效探测距地球遥远天体的方法,并最终确定了这些行星的质量介于月球和木星之间。此前,天文学家常通过微引力透镜现象寻找银河系内的行星。根据广义相对论,遥远处小型天体发出     

宏-微机器人末端惯量特性的数学分析

宏－微机器人是指一个小的机械手附在一个大的机械手末端构成的机器人系统。通过对宏－微机器人运动学、动力学的分析，研究了宏－微机器人的末端惯量特性；数学分析给出了宏－微机器人末端有效惯量的解析表达式，并进一步证明了宏－微机器人有减小末端有效惯量、扩充系统频带的特性。     

星系团Abell 2218的强引力透镜现象

简要介绍了引力透镜，NFW质量分布模型的基本原理．详细讨论了星系团Abell2218的NFW质量分布模型在强引力透镜的应用，估算了星系团的质量及个别背最星系的红移，并对这些结果进行了分析与讨论．     

国家天文台青年学者发现罕见引力透镜光弧

[国家天文台]近日，国家天文台博士生文中略等人从国际巡天数据库SDSS中发现了星系团强引力透镜系统，这是我国学者首次从观测数据中发现引力透镜现象。     

引力透镜现象的研究

描述了引力透镜的观察现象和产生机理,并从光线的偏折和E inste in环的形成对引力透镜的计算方法进行了阐述,总结了引力透镜的研究意义.     

基于浮动定子的超高加速度宏微运动平台设计及隔振分析

突破宏微运动平台加速度限制对于微电子制造业的快速发展具有重要意义。为突破加速度限制,基于"宏+微+宏"驱动模式,提出了一种超高加速宏微运动平台。由超高加速度引起的振动通过浮动定子隔离,以保障超高加速度宏微运动平台超精密定位并获得平台的优越性能。通过搭建基于浮动定子的超高加速度宏微运动平台理论模型,进行理论分析以探究其振动隔离特性。进一步,利用ANSYS软件对宏微运动平台的有限元模型,进行相关瞬态动态仿真分析,对振动隔离进行验证。最后,搭建振动实验平台,在超高加速度下,基于浮动定子的宏微运动平台在频域和时域中振动隔离被验证。研究结果为微电子制造设备升级和制造业的快速发展提供了理论和技术依据。     

基于奇异摄动的宏—微机器人控制方法

物理上包含快过程和慢过程的系统可以用奇异摄动方法分析和控制,通过集中微机械手的小参数,提出了将宏－微机器人的动力学模型表示的为标准的奇异摄动模型的方法,这一方法对刚体连杆机械手具有一般性,基于奇异摄动方法设计了宏－微机器人控制器,宏机械手采用计算力短控制,微机械手采用非线性反馈控制,四自由度宏－微机器人的仿真研究证明了方法的有效性。     

宏—微机器人系统及其连续轨迹控制研究

宏-微机器人即一小机械手附在一大机械手的末端构成的机器人系统，这种机器人有减小末端有效惯量、扩充频带的特性．介绍了研制的宏一微机器人，并进行了连续轨迹跟踪方面的实验研究，取得了满意的结果     

中微子天体和引力透镜

本文讨论了中微天体(NAO)作为引力透镜偏转体的意义和作用。指出:NAO作为偏转体,能使发光体生成五个象。由于观测仪器分辨本领的限制,有时只能观测到三个象或四个象。提出了象亮度的增加导致类星体星等变化的可能性。     

引力透镜现象的概率分布

采用2种GNFW引力透镜模型，计算高红移类星体经引力透镜星多像的概率。一种是在小尺度上选模型参数a=1．5，大角度上选a=1；另一种是在小角度上选a=2，大角度上选a=1．2种模型的结果均证明：星像间夹角△θ0小的透镜的概率要远大于夹角大的透镜的概率。把得到的结果与观测进行比较，可看出第2种模型要符合得更好些。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

橡胶颗粒沥青混合料低温抗裂性试验研究

以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-