A circumstellar disk associated with a massive protostellar object

The formation process for stars with masses several times that of the Sun is still unclear. The two main theories are mergers of several low-mass young stellar objects, which requires a high stellar density, or mass accretion from circumstellar disks in the same way as low-mass stars are formed, accompanied by outflows during the process of gravitational infall. Although a number of disks have been discovered around low- and intermediate-mass young stellar objects, the presence of disks around massive young stellar objects is still uncertain and the mass of the disk system detected around one such object, M17, is disputed. Here we report near-infrared imaging polarimetry that reveals an outflow/disk system around the Becklin-Neugebauer protostellar object, which has a mass of at least seven solar masses (M(o)). This strongly supports the theory that stars with masses of at least 7M(o) form in the same way as lower mass stars.     

热尘埃等离子体中尘埃声波的调制不稳定性

通过约化摄动法,得到了描述具有2种离子温度且尘埃微粒电荷可变的热尘埃等离子体中尘埃声波的非线性薛定谔方程,并研究了热尘埃等离子体中低温离子未受扰动的数密度、低温离子温度、高温离子未受扰动的数密度、高温离子温度、尘埃微粒的温度对尘埃声波调制不稳定性的影响.结果表明,具有2种离子温度且尘埃微粒电荷可变的热尘埃等离子体中尘埃声波是调制稳定的,低温离子未受扰动的数密度是影响尘埃声波调制不稳定性的主要因素.具有2种离子温度且尘埃微粒电荷可变的热尘埃等离子体中仅存在暗孤子.     

Rapid planetesimal formation in turbulent circumstellar disks

During the initial stages of planet formation in circumstellar gas disks, dust grains collide and build up larger and larger bodies. How this process continues from metre-sized boulders to kilometre-scale planetesimals is a major unsolved problem: boulders are expected to stick together poorly, and to spiral into the protostar in a few hundred orbits owing to a 'headwind' from the slower rotating gas. Gravitational collapse of the solid component has been suggested to overcome this barrier. But even low levels of turbulence will inhibit sedimentation of solids to a sufficiently dense midplane layer, and turbulence must be present to explain observed gas accretion in protostellar disks. Here we report that boulders can undergo efficient gravitational collapse in locally overdense regions in the midplane of the disk. The boulders concentrate initially in transient high pressure regions in the turbulent gas, and these concentrations are augmented a further order of magnitude by a streaming instability driven by the relative flow of gas and solids. We find that gravitationally bound clusters form with masses comparable to dwarf planets and containing a distribution of boulder sizes. Gravitational collapse happens much faster than radial drift, offering a possible path to planetesimal formation in accreting circumstellar disks.     

Void and cloud patterns in a dusty plasma

Voids and complex cloud patterns have been observed in a radio frequency (rf) discharge dusty plasma system. The structures and behaviors of these patterns were investigated in two- and three-dimensions by shifting an illumination laser sheet beam up and down.Two-dimensional (2D) circular voids, thin ring voids, and their coexistent voids were observed at the early stage of particle growth. The corresponding three-dimensional (3D) structures were dome, shell, and their coexistent voids, respectively. The complex fluid-like cloud patterns occurred above the 3D dome voids. The origin and evolution process of the complex dust cloud patterns need a further theoretical explanation.     

尘埃等离子体状态方程及其热容量研究

由统计物理学中经典系综理论得到弱耦合尘埃等离子体的状态方程,并与理想气体的状态方程进行了比较.在此基础上,给出了尘埃等离子体近似为理想气体的条件,并得到了强耦合尘埃等离子体热容量的近似表达式.     

Shock wave diffraction and reflection around a dusty square cavity

The diffraction and reflection of planar shock wave around a dusty square cavity is investigated nuerically, which is embedded in the flat bottom surface of a two-dimensional channel, and the induced gas-particle twophase flow. The wave patterns at different times are obtained for three different values of the particle diameter. The computational results show that the existence of particles affects appreciably the shock wave diffraction and cavity flow.     

Low-temperature crystallization of silicate dust in circumstellar disks.

Silicate dust in the interstellar medium is observed to be amorphous, yet silicate dust in comets and interplanetary dust particles is sometimes partially crystalline. The dust in disks that are thought to be forming planets around some young stars also appears to be partially crystalline. These observations suggest that as the dust goes from the precursor clouds to a planetary system, it must undergo some processing, but the nature and extent of this processing remain unknown. Here we report observations of highly crystalline silicate dust in the disks surrounding binary red-giant stars. The dust was created in amorphous form in the outer atmospheres of the red giants, and therefore must be processed in the disks to become crystalline. The temperatures in these disks are too low for the grains to anneal; therefore, some low-temperature process must be responsible. As the physical properties of the disks around young stars and red giants are similar, our results suggest that low-temperature crystallization of silicate grains also can occur in protoplanetary systems.     

圆盘反应器成膜性能的实验研究

在直径为0.48m圆盘反应器内研究了物料黏度、液位、圆盘转速等因素对反应器功率、最小成膜转速、持液量以及膜厚的影响规律。结果表明:最小成膜转速随黏度的增加而降低,随液位的降低而升高;持液量随黏度和转速增加而增大,黏度较低时增加的趋势低于黏度较高时;无因次混合时间随着线速度的增加先减小后增加;同时得到了功率准数以及膜厚的关联式。     

包含双温非热离子的尘埃等离子体中的三维尘埃声孤波

考虑高阶横向扰动的因素,使用约化摄动方法得到描述含有双温非热离子的无磁化尘埃等离子体中的尘埃声波的(3+1)维KP方程.详细讨论一些尘埃等离子体系统参数如电子与非热高温离子数密度v与μh、快离子数λ(α)、低温非热离子与电子的温度比1β、非热双温离子温度比2β对尘埃声孤波性质的影响.研究结果表明:这些因素均可显著影响和改变孤波结构.在考虑双温非热离子后,稀疏形孤波与压缩形孤波的临界条件也发生极大变化.     

含有双温非热离子的热尘埃等离子体中的尘埃声孤波

使用约化摄动方法得到含有双温非热离子的无磁化热尘埃等离子体中的KdV方程.研究结果表明,尘埃流体的温度会严重影响尘埃声孤波的结构,而且允许稀疏形孤波与压缩形孤波共存.     

单盘转子系统受强动载荷作用的刚-塑性动力学响应

通常转子系统的响应分析是在弹性变形假设下进行的,但当转子受到强动载荷撞击时将产生塑性变形。本文结合转子动力学和塑性动力学,分析了单盘转子受强动载荷作用时的刚-塑性动力学响应。首先,将单盘转子系统简化为中间带质量块的简支梁,给出了在阶跃载荷作用下系统的各阶段响应模式。在此基础上,详细讨论了单盘转子在跨度中点受撞击时的动力学响应完全解,并结合龙格-库塔法得到了单盘转子的瞬态变形。所得结果可为转子系统的动力响应和失效分析提供依据。     

Research on the disappearance causes of the Tenghualuo Site in Lianyungang,Jiangsu Province, China

With brilliant civilization during the transitional period from a original clan society to a state society in prehistory,the Neolithic Tenghualuo Site in Lianyungang was discovered by archaeological survey in 1989,which was titled as‘one of the nation’s ten great archeological discoveries in 2000’.However,the transgression and the anthropogenic environment deterioration have ever been employed to explain the abandonment of the site.Based on a dynasty framework established by the 14 C dating,and using the experimental methods such as micro-paleontology identification in foraminifera and charophytes, the content test of Rb and Sr,susceptibility analysis as well as granularity and sedimentary facies analysis,some researches on the sediments from the two exploration layers at Tenghualuo Site were conducted,and the following new findings have been gained:Firstly,foraminifera which are relevant to the marine environment were not found in the sediment layer,however,25 charales,which usually live in the freshwater environment,in 07LTT1 exploration samples were found.Among them,3 charales were found in the samples from the forth sediment layer below the late Longshan Cultural layer and 22 charates were from the second sediment layer above the late Longshan Cultural layer.Furthermore,5 plant seeds and 41 fungal spores,together with many carbonation holes,plant seed shells,as well as their roots and stems were also found in the second sediment layer above the late Longshan Cultural layer.Secondly,the cumulative probability curves of the sediments’granularity in both the last and its overlying culture intermittent layers have characteristics of three-phase river sediment curve,and the ratios between Rb and Sr are both quite high in samples from two layers sedimented during the disappearing time of the site.All above-mentioned evidences indicate that disappearance of the Tenghualuo Site was not related to the transgression.The late Longshan Culture of the site could be completely abandoned after a relatively long-ter     

不对称电极上尘埃等离子体颗粒分布

针对不对称电极射频(radio frequency, RF)辉光放电,通过构建二维尘埃等离子体鞘层模型,研究了不对称电极附近鞘层电势和电子密度等参量分布,并对鞘层中的颗粒进行受力分析,研究了尘埃颗粒在鞘层中的分布特征.结果表明：不对称电极鞘层附近电势具有棘轮势特点,颗粒受鞘层电场约束悬浮在鞘层内,其所在平衡位置处的电势呈现不对称周期性变化.通过对比不同大小的颗粒,发现小颗粒悬浮在鞘层较高位置成链状分布,大颗粒的平衡高度靠近极板,被“钉”到不对称电极产生的势阱中.     

一株啤酒污染菌的分离鉴定及快速检测方法

在成品瓶装啤酒中分离得到1株有害的污染菌。经表型性状分析、生理生化反应、G C含量测定以及16S rDNA序列分析,鉴定为Lactobacillus acetotolerans。建立了1种新的快速鉴定啤酒有害菌的PCR方法,这种方法基于抗酒花基因horA的部分序列。用传统的检测方法检测有害菌需要8~10 d,而用新的PCR方法仅需24~32 h。     

The development of a protoplanetary disk from its natal envelope

Class 0 protostars, the youngest type of young stellar objects, show many signs of rapid development from their initial, spheroidal configurations, and therefore are studied intensively for details of the formation of protoplanetary disks within protostellar envelopes. At millimetre wavelengths, kinematic signatures of collapse have been observed in several such protostars, through observations of molecular lines that probe their outer envelopes. It has been suggested that one or more components of the proto-multiple system NGC 1333-IRAS 4 (refs 1, 2) may display signs of an embedded region that is warmer and denser than the bulk of the envelope. Here we report observations that reveal details of the core on Solar System dimensions. We detect in NGC 1333-IRAS 4B a rich emission spectrum of H2O, at wavelengths 20-37 microm, which indicates an origin in extremely dense, warm gas. We can model the emission as infall from a protostellar envelope onto the surface of a deeply embedded, dense disk, and therefore see the development of a protoplanetary disk. This is the only example of mid-infrared water emission from a sample of 30 class 0 objects, perhaps arising from a favourable orientation; alternatively, this may be an early and short-lived stage in the evolution of a protoplanetary disk.     

带止步、中途退出N策略温贮备机器维修问题

研究了具有温贮备备用部件,故障机器带止步、中途退出的N策略机器维修问题。采用分块矩阵的技术得到了系统稳态可用度、故障频度、首次故障前的平均时间的简洁直观的稳态概率向量的迭代公式,最后进行了数值分析,考察了系统参数变化对系统可靠性性能指标的影响。     

用Disk Manager2000管理和维护大容量硬盘

详细介绍了利用 Disk Manager2000对新硬盘进行安装及安装中盘符交错的问题。安装后如何对硬盘进行维护、分区等。其中介绍了重新分区、正确定位光驱盘符、不同盘之间的文件拷贝,以及怎样创建 For Dos 的启动盘。同时介绍了硬盘检测工具 Run SmartedFender 使用方法。