Unveiling the chemistry of hot protostellar cores with ALMA

High angular resolution mm-wave observations of the Orion-KL region, made with the IRAM Plateau de Bure interferometer (PdBI), reveal the presence of several cores of size 10³ AU, which have distinct spectral signatures. Complex molecules such as ethanol, vinyl cyanide and dimethyl ether show different distributions and their relative abundance varies from core to core by orders of magnitude. The molecular column densities derived in the cores also differ widely from the beam-averaged column densities observed with large single-dish telescopes. Obviously, the predictions of hot core chemistry models must be checked against high resolution observations. ALMA, which allies sensitivity and high angular resolution, will be a key instrument for this type of studies. The PdBI observations were part of a search for interstellar glycine, also carried out with the IRAM 30-m telescope and the Green Bank Telescope. We derive a 3σ upper limit on the column density of glycine of 1×10¹⁵ cm⁻² per 2″×3″ beam in the Orion Hot Core and Compact Ridge. Based on observations made with the IRAM PdB Interferometer, the IRAM 30-m telescope and the NRAO Green-Bank telescope. IRAM is supported by CNRS, MPG and IGN.     

Revisiting vertical structure of neutrino-dominated accretion disks: Bernoulli parameter, neutrino trapping and other distributions

We revisit the vertical structure of neutrino-dominated accretion flows (NDAFs) in spherical coordinates with a new boundary condition based on the mechanical equilibrium. The solutions show that NDAF is significantly thick. The Bernoulli parameter and neutrino trapping are determined by the mass accretion rate and the viscosity parameter. According to the distribution of the Bernoulli parameter, the possible outflow may appear in the outer region of the disk. The neutrino trapping can essentially affect the neutrino radiation luminosity. The vertical structure of NDAF is like a “sandwich”, and the multilayer accretion may account for the flares in gamma-ray bursts.     

回声测深仪在水下地形测量中的应用

本文在介绍回声测深仪基本工作原理的同时,介绍了回声测深仪在杭州湾口外一拟建大型码头下地形测量的一个应用实例。     

Experimental Study and Fatigue Analysis of Vortex-Induced Vibration of Umbilical Cable Considering Internal Friction

In order to investigate the effect of internal friction of umbilical cable on its vortex-induced vibration(VIV)responses, the experimental study on VIV of bond umbilical cable(BUC) and un-bond umbilical cable(UBUC) was carried out in an experimental tank. A current generator in the laboratory simulated the uniform current, and the current velocities were observed in real time by using a Doppler Velocimeter. In addition, different sizes of top tension were applied to the umbilical cable model. The VIV responses of the umbilical cable model were measured by using Fiber Bragg grating(FBG) strain sensors. The displacement responses of umbilical cable model were reconstructed based on the experimental strain data processed by modal superposition method. In this paper, the traveling wave characteristics, the spatial-temporal distribution characteristics of frequency and fatigue damage of the BUC and UBUC under VIV are studied. The experimental results show that there are obvious differences between BUC and UBUC in the response characteristics of VIV. The UBUC appears the traveling wave sooner than BUC, but its standing wave characteristics are more obvious than those of BUC at high velocities. Compared with BUC, the spatial-temporal distribution of UBUC frequencies appears wide-band distribution sooner, but has narrower bandwidth in the "lock-in" state. The level of fatigue damage of BUC was approximately the same as that of UBUC.     

北太平洋副热带模态水盐度的年代际变化

副热带模态水(Subtropical Mode Water;STMW)在气候变化中起着重要作用。本文利用全球高分辨率数值模拟结果,研究了北太平洋STMW核心层盐度(Core Layer Salinity;CLS)的年代际变化及其物理机制。结果表明,CLS存在显著的年代际变化,其空间分布则与背景流场分布特征有关。侵蚀区CLS滞后生成区CLS约1~2年,这主要是海流平流输运引起的。生成区内,STMW的季节循环一般可分为生成期(12-4月)、隔离期(5-6月)和侵蚀期(7-11月),生成期混合层盐度(Mixed Layer Salinity;MLS)决定着隔离期和侵蚀期的CLS,而MLS年代际变化则主要由同太平洋年代际涛动存在负相关性的海表面淡水通量的变化引起。     

电活化硫酸盐处理四环素类废水的研究

本文构建以掺硼金刚石(Boron-doped diamond,BDD)为阳极、不锈钢为阴极、硫酸盐为电解质的电化学体系,考察了电流密度、pH值、硫酸盐浓度以及初始四环素浓度等四个因素对电化学氧化降解废水中四环素的影响,运用响应曲面法对运行参数进行优化;通过电子自旋共振检测技术分析电化学反应中产生的自由基,探究了间歇通电模式下电化学体系持续氧化机理。结果表明,四个因素对TOC去除率的影响大小次序为:电流密度>初始四环素浓度>初始pH值>硫酸盐浓度,其中初始pH值和硫酸盐浓度与电流密度和初始四环素浓度的交互作用对TOC去除率的影响较为显著;最佳运行参数为pH值为5,电流密度为100 mA·cm^-2,硫酸盐浓度为0.25 mol·L^-1,初始四环素浓度为1000 mg·L^-1;间歇通电模式下,BDD电极表面产生的SO₄^·-等高活性物质间相互转化提供了体系的可持续氧化能力。该研究结果为电化学氧化技术的实际应用提供了节省能耗的有效途径。     

Optimization of 3D building models by GPS measurements

GPS Solutions - Recently, 3D building models have become an important aid to many positioning methods such as LiDAR and GPS positioning. Creating an accurate 3D building model requires accurate 2D...     

安徽宣城红土微生物GDGTs分布特征及其古环境意义

中国南方更新世红土是古气候环境变化研究非常重要的载体之一,红土微生物类脂分子是其古气候环境研究的有效指标,但其在红土中的古气候意义需要更进一步的挖掘和明确.选取处于气候变化敏感地带并且已有很好年代学基础的安徽宣城红土剖面进行详细的野外调查和系统的样品采集,利用改善后的碱式水解法提取红土微生物类脂分子,通过对比分析、比较印证等方法对其中的甘油二烷基链甘油四醚(glycerol dialkyl glycerol tetraethers,简称GDGTs)进行系统研究.宣城剖面GDGTs分布特征显示:剖面下部各指标呈旋回性变化、而上部相对稳定,表明形成初期环境比较动荡,而后期成土环境相对稳定;土壤pH为7.0~8.0,推测其物源主要来源于北方干旱区或长江中下游干涸河滩沉积;BIT指标反映宣城地区在130 ka BP左右气候极为干旱.结果表明,红土中微生物类脂物GDGTs能够定量、高分辨率地重建安徽宣城的古气候环境,具有重要的研究意义.      

钢筋混凝土柱考虑损伤累积的反复荷载-位移关系分析

为能在反复荷载作用下钢筋混凝土柱的荷载-位移关系分析中考虑柱低周疲劳性能,提出了一损伤模型,对柱中纵向受力钢筋和混凝土的损伤状态作评估与记录。将这一记录材料性能信息的损伤指标带入材料各自的恢复力模型以考虑产生损伤后材料的强度和刚度退化。基于多弹簧模型对不同变幅加载路径下及等幅低周疲劳加载下钢筋混凝土柱的空间反应进行了数值计算模拟。与已有试验结果比较表明,所提材料层次上的损伤累积模型以及考虑损伤累积效应的柱构件空间荷载-位移关系分析方法具有一定的精度,为钢筋混凝土柱的抗震性能分析提供了一个辅助工具。