Inertia-Centric Stability Analysis of a Planar Uniform Dust Molecular Cloud with Weak Neutral-Charged Dust Frictional Coupling

This paper adopts an inertia-centric evolutionary model to study the excitation mechanism of new gravito-electrostatic eigenmode structures in a one-dimensional（1-D） planar self-gravitating dust molecular cloud（DMC） on the Jeans scale.A quasi-neutral multi-fluid consisting of warm electrons,warm ions,neutral gas and identical inertial cold dust grains with partial ionization is considered.The grain-charge is assumed not to vary at the fluctuation evolution time scale.The neutral gas particles form the background,which is weakly coupled with the collapsing grainy plasma mass.The gravitational decoupling of the background neutral particles is justifiable for a higher inertial mass of the grains with higher neutral population density so that the Jeans mode frequency becomes reasonably large.Its physical basis is the Jeans assumption of a self-gravitating uniform medium adopted for fiducially analytical simplification by neglecting the zero-order field.So,the equilibrium is justifiably treated initially as ＂homogeneous＂.The efficacious inertial role of the thermal species amidst weak collisions of the neutral-charged grains is taken into account.A standard multiscale technique over the gravito-electrostatic equilibrium yields a unique pair of Korteweg-de Vries（KdV） equations.It is integrated numerically by the fourth-order Runge-Kutta method with multi-parameter variation for exact shape analyses.Interestingly,the model is conducive for the propagation of new conservative solitary spectral patterns.Their basic physics,parametric features and unique characteristics are discussed.The results go qualitatively in good correspondence with the earlier observations made by others.Tentative applications relevant to space and astrophysical environments are concisely highlighted.

Star Formation in Self-Gravitating Molecular Cloud: The Critical Mass and the Core Accretion Rate

Understanding how stars form in molecular clouds is one of the ongoing research areas in astrophysics. Star formation is the fundamental process to which our current understanding remains incomplete due to the complexity of the physics that drives their formation within molecular clouds. In this article theoretical modelling of the lowest possible mass of the cloud needed for collapse and the core accretion rate has been presented for the molecular cloud collapsing under its gravity. In many of previous studies the critical mass of star forming cloud under its gravity has been modelled using kinetic energy and gravitational potential energy. However, we test the effect of thermodynamic efficiency factor together with other physical processes in describing the critical mass, and controlling or triggering the rate of mass falling onto the central core. Assuming that, the ratio of radiation luminosity to gravitational energy released per unit time of the collapsing MC is less than unity. Following this conceptual framework we have formulated the critical mass and the core accretion rate of the self-gravitating molecular cloud.

Star Formation in Magnetized, Turbulent and Rotating Molecular Cloud: The Critical Mass

In this paper, we present the critical mass of magnetized, turbulent and rotating star-forming molecular cloud core (MCc) in the presence of magnetic tension. The critical mass of star-forming magnetized cloud is influenced by the magnetic tension, magnetic pressure and other pressures. Applying the method of theoretical modelling by taking into account the basic equations and assumptions, we formulate the critical mass of magnetized MCc in different cases. Accordingly, the minimum critical masses we find in both cases are different. Energy due to magnetic tension significantly triggers the collapse at relatively larger radius of the core. The model shows that when the initial radius of the parent cloud (Ro) is larger than that of collapsing core radius (Rcore) the magnetic tension also has the larger radius of curvature, so it plays a significant role in supporting gravity to collapse the core. The results indicate gravity without magnetic tension may not overcome magnetic pressure, turbulence pressure and pressure due to rotation. This shows the critical mass of MCc for the collapse depends on the tension force that magnetic field lines apply on the envelope. We conclude that if there is magnetic pressure in star-forming MCc, there is also unavoidable magnetic tension, which triggers the collapse of the core. If there is no magnetic tension, the magnetized MCc needs relatively larger mass and higher density within the small size to collapse.

Shanghai TMRT discovered a new dense molecular cloud rich in long carbon-chain molecules

With the support by the National Natural Science Foundation of China and the Chinese Academy of Sciences,the research team led by Prof.Shen Zhiqiang(沈志强)at the Division of Radio Astronomy Science and Technology,Shanghai Astronomical Observatory,Chinese Academy of Sciences,discovered a new dense molecular cloud rich in long carbon-chain molecules,which was published in Astrophysical

350 μm map of the Ophiuchus molecular cloud: core mass function

Stars are born in dense cores of molecular clouds. The core mass function(CMF), which is the mass distribution of dense cores, is important for understanding the stellar initial mass function(IMF). We obtained 350 μm dust continuum data using the SHARC-II camera at the Caltech Submillimeter Observatory(CSO) telescope. A 350 μm map covering 0.25 deg2 of the Ophiuchus molecular cloud was created by mosaicing 56 separate scans. The CSO telescope had an angular resolution of 9′′, corresponding to 1.2×103AU at the distance of the Ophiuchus molecular cloud(131 pc). The data was reduced using the Comprehensive Reduction Utility for SHARC-II(CRUSH). The flux density map was analyzed using the Gauss Clumps algorithm, within which 75 cores has been identified. We used the Spitzer c2 d catalogs to separate the cores into 63 starless cores and 12 protostellar cores. By locating Jeans instabilities, 55 prestellar cores(a subcategory of starless cores) were also identified. The excitation temperatures, which were derived from FCRAO12 CO data, help to improve the accuracy of the masses of the cores. We adopted a Monte Carlo approach to analyze the CMF with two types of functional forms; power law and log-normal. The whole and prestellar CMF are both well fitted by a log-normal distribution, with μ =-1.18±0.10, σ = 0.58±0.05 and μ = 1.40±0.10, σ = 0.50±0.05 respectively. This finding suggests that turbulence influences the evolution of the Ophiuchus molecular cloud.

Molecular clouds associated with compact HII regions in Galactic plane

13CO (J = 1 - 0) emission of massive star forming region including 15 ultracompact and 4compact HII regions in Galactic plane was mapped with the 13.7 m millimeter wave telescope of Purple Mountain Observatory. The present observations provide the first complete structure of the clouds in 13CO with a higher spatial resolution and a wide-field coverage of 28′×45′. Combined with the images of far-infrared emission and dust color temperature obtained from ISSA, various possible dynamical connections between the compact HII regions and associated clouds were found. We presente some reasons to explain the formation of new dense cold core and molecular emission cavity in the massive star formation and early evolution. The luminosities of excitation stars for all HII regions and the main parameters of associated clouds are also derived. The results show that the newborn stars' luminosities are correlated with the 13CO column densities, masses (in 55'beam) and 13CO velocity widths obviously.

^(13)CO mapping study for massive molecular cloud cores

Using the newly installed SIS receiving system on the 13.7 m telescope at Qinghai Station of PMO, United Radio Astronomy of CAS, CO isotope 13 CO J=1-0 and C18 O J=1-0 lines were observed for thr ee sources S241, S39 and ON3. Results show that the three sources have massive cor es, of which the size is ～2-5 pc, masses are ～103-104 M⊙. The wid t hs of lines are also larger than those in low mass cores. And high velocity char acteristics were observed for all the sources. The V LSR distribution p resents rotation of the core in ON3. And all the three cores contain deeply embe dded forming massive stars. The young stellar objects in S241 and ON3 seem to be moving away from their birth sites.

Charging Mechanism of Lightning at the Molecular Level

Cloud electrification is one of the oldest unresolved puzzles in the atmospheric sciences. Though many mechanisms for charge separation in clouds have been proposed, a quantitative understanding of their respective contribution in a given meteorological situation is lacking. Here we suggest and analyze a hitherto little discussed process. A qualitative picture at the molecular level of the charge separation mechanism of lightning in a thundercloud is proposed. It is based on two key physical/chemical natural phenomena, namely, internal charge separation of the atmospheric impurities/aerosols inside an atmospheric water cluster/droplet/ice particle and the existence of liquid water layers on rimers (graupels and hailstones) forming a layer of dipoles with H+ pointing out from the air-water interface. Charge separation is achieved through strong collisions among ice particles and water droplets with the rimers in the turbulence of the thundercloud. This work would have significant contribution to cloud electrification and lightning formation.

南昌前湖区域夏季降水中低分子有机酸的分布与来源

2020年5—9月,共采集南昌前湖区域20个降水事件的88个分段降水样品,测定降水中3种低分子有机酸(甲酸、乙酸、草酸)和4种无机阴离子(Cl^(-)、NO_(2)^(-)、NO_(3)^(-)、SO_(4)^(2-))浓度,分析讨论降水有机酸的分布、来源,定量解析云下冲刷、云水对降水有机酸的贡献.结果表明,降水中甲酸、乙酸、草酸占所测定阴离子总量的16%,降水有机酸与无机酸总量的月变化呈相反趋势;长降水事件的降水有机酸浓度在降水进程中呈现先逐渐降低,到降雨末期趋于平稳或稍稍反升的变化特征;降水进程中,云下冲刷对降水中3种有机酸的贡献率逐渐减小,而云水对其贡献率逐渐增大,降雨前期,云下冲刷为降水中有机酸根的主要来源,降雨后期,以云水贡献为主;前期降水中3种有机酸两两之间的相关性比末期降水中的弱,降水中草酸与SO_(4)^(2-)的相关性较甲、乙酸与SO_(4)^(2-)的相关性强,反映降水中草酸受二次污染影响大;基于甲酸/乙酸比值(F/A)分析,南昌地区5、9月降水有机酸受二次有机物影响较大,6—8月降水有机酸主要来源于植物直接排放;因子分析结果表明降水有机酸受酸性气溶胶、燃烧源、植物排放源的影响;PMF分析结果表明燃烧源、二次颗粒的冲刷和植被排放源对降水有机酸的影响.

超临界CO_(2)中烷基聚醚的溶解规律研究

通过浊点压力实验考察了温度、聚合度、烷基链长度以及烷基聚醚含量对烷基聚醚在超临界CO_(2)中溶解度的影响,采用分子动力学模拟计算分析了烷基聚醚分子间相互作用、烷基聚醚和CO_(2)之间的相互作用,并探索了烷基聚醚与CO_(2)的微观相溶规律。实验结果表明,温度升高,烷基聚醚在超临界CO_(2)中的溶解度减小,烷基聚醚与CO_(2)之间的亲和性降低;在分子中引入聚氧丙烯基团有利于提高烷基聚醚在超临界CO_(2)中的溶解度,但存在最佳聚合度范围。十二烷基聚氧丙烯醚比十二烷基聚氧乙烯醚的溶解度参数小,分子间相互作用更弱,且在超临界CO_(2)中更分散,与CO_(2)的相互作用能更大,使其与CO_(2)亲和性更强,浊点压力更低,溶解度更好。

沥青质分子支链及桥链断裂行为的模拟计算

用分子模拟方法对含有支链的大陆型沥青质分子和群岛型沥青质分子的断裂位置及断键规律进行研究,并对支链断裂反应进行了热力学计算。结果表明:对于大陆型沥青质分子,其支链断裂的位置均在β位,支链小于3个碳原子时,C—C键较难断裂,支链越长越容易断裂;从热力学上看,大陆型沥青质分子支链断裂的转化率较高,断键反应没有障碍,反应的深度由动力学条件来控制;对于群岛型沥青质分子,其断键位置在稠环芳烃数较多片断的β位容易断裂,当链段小于3个碳原子时,C—C桥键很难断裂,桥链越长断裂的活化能越低,越容易断裂。对于C—S桥键,其断裂的活化能比C—C桥键的低,断裂相对容易。

大质量年轻星体新的C^(18)O(1-0)发射

利用紫金山天文台青海观测站１３．７米的毫米波望远镜对７４个大质量年轻星体或候选体进行了 Ｃ～（１８）Ｏ（１－０）的谱线观测．在６３个源中观测到了Ｃ～（１８）Ｏ（１－０）发射，其中 ５７个天体第一次探测到Ｃ～（１８）Ｏ（１－０）谱线发射．艰据谱线辐射温度（ＴＲ＊）和半宽（△Ｖ），利用ＬＴＥ方法计算了每个测量源的 Ｃ～（１８）Ｏ（１－０）发射的光学厚度和 Ｃ～（１８）Ｏ分子的柱密度，讨论了１３ＣＯ（１－０）和Ｃ～（１８）Ｏ（１－０）的谱线强度比和积分强度比．

正负离子表面活性剂与非离子表面活性剂混合水溶液的相互作用

非离子表面活性剂的加溶作用有助于正负离子表面活性剂的溶解,在恰当比例时,能基本保持其表面活性;正负离子表面活性剂与非离子表面活性剂之间的相互作用很弱,容易形成接近“理想”的混合胶团;恒定非离子表面活性剂浓度时,随正负离子表面活性剂浓度增加,溶液的浊点也增加;超过临界胶团浓度后浊点下降。

基于LAMMPS系统的集群运算系统架构

为解决分子动力学计算系统LAMMPS(Large-scale Atomic/Molecular Massively Parallel Simulator)运算数据量大、不易控制的问题,应用云计算方法,设计了智能化、高效化的集群LAMMPS运算系统架构。该架构将FTP(File Transfer Protocol)存储技术、UDP(User Datagram Protocol)快速网络传输、LAMMPS分子动力学计算技术相结合,降低了运算过程中的人工干预,提高了分子模型处理效率,并为分子级别物理、化学的计算机仿真研究提供了新的集群化解决方案。

分子云核与恒星形成区的良好探针－CH_3CN

本文作者通过对猎户座ＫＬ区的观测、分析与计算，阐明ＣＨ３ＣＮ分子转动谱线系作为分子云核与恒星形成区探针的可能性和优越性．并对观测该线系所需要的仪器条件进行了讨论．

大质量年轻星体的^(13)CO(1→0)谱线发射

利用紫金山天文台青海站的 13.7m毫米波望远镜对 133个大质量年轻星体或其候选体进行了 13CO( 1→ 0 ) ( J=1→ 0 )的谱线观测 .在 115个源中观测到了 13CO( 1→ 0 )的发射 ,其中 94个天体是第一次探测到 13CO( 1→ 0 )谱线 .根据多样性的 13CO( 1→ 0 )谱线轮廓 ,分析了大质量年轻星成协分子云核的运动和结构 .用 L TE方法导出了每个被测源的 13CO( 1→ 0 )光学厚度和 H2 分子柱密度 .计算了 8个与大质量年轻星候选体成协分子云核的 mvir/mcl。

基于MD-CM-SFLA神经网络的耳语音情感识别

提出了一种基于分子动力学模拟与云模型理论的改进混合蛙跳算法(MD-CM-SFLA).该算法将青蛙个体等效成分子,仅考虑最差个体和全局最优个体之间的吸引力,采用一种新的分子间作用力来代替两体间经典的Lennard-Jones作用力,并利用Velocity-Verlet算法和正态云发生器代替混合蛙跳算法的更新策略,有效平衡了种群的多样性和搜索的高效性.然后,将MD-CM-SFLA算法与BP神经网络相结合,设计出一种MD-CM-SFLA神经网络,并将其应用于耳语音情感识别中.耳语音情感识别结果表明,MD-CM-SFLA神经网络相对于BP神经网络具有明显的优势,在相同的测试条件下,其平均识别率较BP神经网络提高5.2%.由此表明,利用MD-CM-SFLA算法优化BP神经网络的参数,可以实现BP神经网络的快速收敛,获得较好的学习能力,从而为耳语音情感识别提供一种新思路.

NGC 1333/IRAS6-9区域中的致密分子云核

利用紫金山天文台青海站的13．7m毫米波望远镜，对NGC1333／IRAS6－9附近的一个10．3'X10'和6．8'X8'的恒星形成区，进行了13CO（1－0）和C18O（1－0）的成图观测，发现了多个新的分子云核和沿SSV12－IRASS方向的13CO（1－O）双极外向流．本文给出了每个云核的观测特性和物理参数．分析了这一区域的云核分布和速度场结构．详细讨论了该区域的云核分布、双极外向流和群集的年轻天体、红外源以及HH天体的关系．

表面活性剂水溶液池热核沸腾传热的试验研究

对表面活性剂SDS、CTAB、Triton X-114和Triton X-100水溶液物性及其池核沸腾传热进行了试验,重点探讨了表面活性剂分子结构参数和溶液物性对沸腾传热的影响。结果表明:表面活性剂溶液沸腾传热效果、表面活性剂相对分子质量对表面活性剂溶液沸腾传热的影响规律都与表面活性剂的电离特性密切相关,离子型表面活性剂SDS与CTAB溶液的沸腾传热系数比值与相对分子质量的比值成-0.22的指数关系,而非离子表面活性剂Triton X-114和Triton X-100溶液不存在指数关系。动态表面张力和热流密度相等时,SDS和CTAB溶液沸腾传热特性差异主要受相对分子质量和平衡接触角的影响,而Triton X-100和Triton X-114溶液则受质量分数、EO基团数、浊点和动力黏度的综合作用。

改进的混合蛙跳算法及其应用

针对混合蛙跳算法(SFLA)后期搜索速度变慢,容易陷入局部极值的缺点,提出一种改进的混合蛙跳算法(ISFLA)。借鉴分子动力学模拟思想,将正态云模型云滴的随机性和稳定倾向性特点应用于比例积分微分(PID)控制器的参数整定中。ISFLA将青蛙个体等效成分子,提出一种新的分子间作用力。利用Velocity-Verlet算法和正态云发生器代替SFLA的更新策略,平衡了搜索的高效性和种群的多样性。仿真结果表明:ISFLA提高了收敛精度、收敛速度、寻优时间、稳定性和后期跳出局部极值的能力,其全局寻优能力优于SFLA;基于ISFLA整定的PID控制器具有良好的鲁棒性、优良的抗干扰性和满意的闭环控制效果。