Study on low‐strain integrity testing of pipe‐pile using the elastodynamic finite integration technique

This study focuses on the three‐dimensional (3‐D) characteristics of wave propagation in pipe‐pile using elastodynamic finite integration technique. First, a real 3‐D pile‐soil model in cylindrical coordinate system is presented. Then, the governing equations are established. With the boundary and initial conditions, the numerical solution is obtained. The accuracy and feasibility of the self‐written code are further verified via comparing with the measured data. Velocity histories at different angles of pile top and pile tip are illustrated, and the snapshots reflecting the 3‐D characteristics of wave propagation are given. It shows that the interferences of Rayleigh waves can confuse the result interpretation for pile integrity testing. The increase of hammer contact time can effectively mitigate the interferences, and the interferences of Rayleigh waves are weakest at an angle of 90° from where hammer hits. Besides, surrounding soil can partly mitigate the wave interferences. Copyright © 2012 John Wiley & Sons, Ltd.     

Electron density diagnostic potential of the Si x ion and its application in Procyon

Theoretical electron density sensitive line ratios   R ₁– R ₆  of Si  x soft X-ray emission lines are presented. We found that these line ratios are sensitive to electron density n _e, and the ratio R ₁ is insensitive to electron temperature T _e. For reliable determination of the electron density of laboratory and astrophysical plasmas, atomic data, such as electron impact excitation rates, are very important. Our results reveal that the discrepancy of the line ratios from different atomic data calculated with the distorted wave (DW) approximation and the R-matrix method is up to 19 per cent at   n _e= 2 × 10⁸ cm⁻³  . We applied the theoretical intensity ratio R ₁ to the Low Energy Transmission Grating Spectrometer (LETGS) spectrum of the solar-like star Procyon. By comparing the observed value (1.29) with the theoretical calculation, the derived electron density n _e is  2.6 × 10⁸ cm⁻³  , which is consistent with that derived from  (C  v < 8.3 × 10⁸ cm⁻³)  . When the temperature structure of the Procyon corona is taken into account, the derived electron density increases from   n _e= 2.6 × 10⁸  to  2.8 × 10⁸ cm⁻³  .     

Voids in a ΛCDM universe

We study the formation and evolution of voids in the dark matter distribution using various simulations of the popular Λ cold dark matter cosmogony. We identify voids by requiring them to be regions of space with a mean overdensity of −0.8 or less – roughly the equivalent of using a spherical overdensity group finder for haloes. Each of the simulations contains thousands of voids. The distribution of void sizes in the different simulations shows good agreement when differences in particle and grid resolution are accounted for. Voids very clearly correspond to minima in the smoothed initial density field. Apart from a very weak dependence on the mass resolution, the rescaled mass profiles of voids in the different simulations agree remarkably well. We find a universal void mass profile of the form  ρ(< r )/ρ( r _eff) ∝ exp[( r / r _eff)^α]  , where r _eff is the effective radius of a void and  α∼ 2  . The mass function of haloes in voids is steeper than that of haloes that populate denser regions. In addition, the abundances of void haloes seem to evolve somewhat more strongly between redshifts ∼1 and 0 than the global abundances of haloes.     

弱磁场及甚强磁场下奇异夸克物质Urca过程的中微子能量损失率

研究了磁场对奇异星模型中夸克直接Urca过程的中微子能量损失率的影响,首先改进了弱场条件下的近似计算方法,这一方法可以推广到其他弱作用过程．在甚强磁场下,严格地计算Urca过程的中微子能量损失率,结果显示辐射率强烈地依赖于磁场,与磁场的二次方成正比,更重要的是对温度的依赖关系不同于弱场及没有磁场时的情形．     

钟房环境自动监测系统的研制

介绍了一种自行研制的钟房环境自动监测系统，该系统由温度、湿度、电压、烟雾等的传感器、信号调理、数据采集和报警等部分组成。长期试运行的结果表明系统达到了预期设计要求。     

The blown sand disaster to the Tarim Desert Highway in Xinjiang,China

The Tarim Desert Highway in Xinjiang, China, the longest one in the world, has a length of 562 km, about 80% of which runs across, from north to south, the Taklimakan Desert. Obviously, the main problem of the road maintenance is the blown sand disaster. The research results showed: (1) the physical environment along the desert highway is characterized by strong winds, fine and loose ground materials, different dunes and so on, which provides the dynamical condition and material source for the formation of blown sand disaster to the road and its shelter system. Meanwhile, the trend and cross-section of the road and the structure of the shelter system, as damage objects, play important roles in the formation process of blown sand disaster; (2) the blown sand disaster to the shelter system is original from the intrusion of the drift sands and mobile dunes outside the shelter system, and the wind erosion and sand deposit caused by the air stream changes on the ground in the shelter system. The main damage object in the Tarim Desert Highway is the shelter system presently. The damage forms include wind erosion, sand burying and dune covering; and (3) the damaged length of the blocking sand fences is 83.7%, 88.4%, 72.4%, 72.8% and 40.3% and the damaged area of the straw checkerboard belts is 73.1%, 58.2%, 44.5%, 35.4% and 36.6%, in turn, in 5 different landform units from north to south, and, the disasters to fences and the straw checkerboard belts are 79.5% and 57.6% in the compound dunes while they are 64.6% and 37.7% in the interdunes respectively.

     

Spectrum characteristics of major ion concentrations at Wuhan sectoin of the Changjiang Rriver

Spectrum analyses of water quality time series have been carried out for five hydrometric stations including Wuhan hydrometric station of the Changjiang(Yangtze) River, etc. The fluctuations of Ca²⁺, Mg²⁺ and HCO ₃ ⁻ concentrations in river water under different physical geography conditions have about two-year cycle which is corresponding to hydrometeorological quasi-biannual-oscillation (QBO). Na⁺, Cl⁻ SO ₄ ²⁻ have about two-year cycle in the area lightly affected by human activities while two-year cycle doesn’t exist in the area heavily affected by human activities. All the fluctuations of major ions have about three-month cycle. The river diseharge fluctuation accounts for 43.9%, 45.1%, 54.3%, 33.9%, 30.3% and 42.7% of the variance of Ca²⁺, Mg²⁺, HCO ₃ ⁻ , Na⁺, Cl⁻, SO ₄ ²⁻ , respectively, at Wuhan from 1962 to 1985. According to the spectrum characteristic of major ions, the duration of the time series has to be at least 13 years for trend analysis of monthly water quality data. Foundation item: Under the auspices of the National Natural Science Foundation of China (No. 49671017). Biography: XIA Xing-hui(1971-), female, a native of Hunan Province, Ph. D. Her research interest includes environmental chemistry.     

南大洋氟的生物地球化学研究——Ⅰ.南极磷虾富氟异常的研究

本文通过对南极磷虾不同部位中氟含量的测定,结合氟在测区环境中的分布特征及南极磷虾体中其它元素的分析资料,讨论了氟在磷虾体内的分布和赋存形式,并对其可能的富集机理及与环境的关系作了初步的探讨。     

Data assimilation with a barotropically unstable shallow water system using representer algorithms

The cycling representer algorithm of Xu and Daley (2000) is a weak constraint four-dimensional variational data assimilation algorithm. It was successfully applied to a one-dimensional transport problem and was able to successfully extract the signal from noisy and sparse observations. The algorithm, however, has not previously been applied to a multivariate, multidimensional system with dynamic instability. The algorithm is also very computationally demanding and awaits considerable enhancement in computer power before being practical for operational forecast models. We have two objectives in this paper. The first is to apply the cycling representer algorithm to a two-dimensional, multivariate barotropically unstable linear shallow water system. The second objective is to formulate and test an accelerated representer algorithm that is much more computationally tractable than the cycling representer algorithm itself. A linear shallow water system with a barotropically unstable basic state was used as a test bed to conduct data assimilation experiments. The evolution of a 'neutral' eastward-propagating singular vector was selected as the 'truth', against which all data assimilation experiments were to be evaluated. The results indicated that the cycling representer algorithm was capable of providing satisfying state estimates for a multivariate, multidimensional system. The results from the accelerated representer algorithm were very encouraging because it is sufficiently computationally tractable to be used on present day multi-processor machines for operational applications.