Aerodynamic Characteristics of the Crest with Membrane Attachment on Cretaceous Pterodactyloid Nyctosaurus

The Nyctosaurus specimen KJ1 was reconstructed under the hypothesis that there is a membrane attached to the crest; the so-called headsail crest. The aerodynamic forces and moment acting on the headsail crest were analyzed. It was shown that KJ1 might adjust the angle of the headsail crest relative to the air current as one way to generate thrust (one of the aerodynamic forces, used to overcome body drag in forward flight) and that the magnitude of the thrust and moment could vary with the gesture angle and the relative location between the aerodynamic center of the headsail crest and body’s center of gravity. Three scenarios were tested for comparison: the crest with membrane attachment, the crest without membrane attachment and the absence of a cranial crest. It was shown that the aerodynamic characteristics (increasing, maintaining and decreasing thrusts and moment) would have almost disappear in flight for the crest without membrane attachment and was non-existent without the cranial crest. It is suggested from aerodynamics evidence alone that Nyctosaurus specimen KJ1 had a membrane attached to the crest and used this reconstructed form for auxiliary flight control.     

2003年9月27日中、俄、蒙边界Ms7.9地震震源机制及破裂过程研究

从IRIS全球数字地震台网长周期记录中, 选取震中距位于30deg;~90deg;的垂直向远震P波资料, 反演了2003年9月27日中、 俄、 蒙边界MS7.9地震及10月1日MS7.3强余震的地震矩张量解, 研究了MS7.9地震的时空破裂过程. 参考余震的空间分布及周围断层走向, 确定MS7.9地震发震断层走向127deg;、倾角为79deg;、滑动角为171deg;. MS7.9地震震源破裂过程反演结果表明,整个破裂过程持续了37 s,释放标量地震矩0.97times;1020 Nmiddot;m. 破裂主要发生在长110 km, 宽30 km的中地壳以上,最大位错3.6 m. 起始破裂处不是滑动量最大的地方. 断层面上显示出两个显著的、滑动量超过2.0 m的破裂区. 破裂传播至MS7.3震源区附近时, 滑动量迅速减小,显示出破裂传播过程的受阻停止, 反映了障碍体引起的破裂过程的不均匀性.      

Parametric study for optimal design of large piled raft foundations on sand

In designing piled raft foundations, controlling the total and differential settlements as well as the induced bending moments of the raft is crucial. The majority of piled raft foundations have been designed by placing piles uniformly. In such a design method, the settlements of the piled rafts are likely to be large, which leads to an increase of the pile length and/or number of piles required to reduce the settlements. However, this increase does not satisfy the requirement for economical design. On the basis of a parametric study, this paper contributes a framework for considering an economical design methodology in which piles are placed more densely beneath the column positions when the piled raft is subjected to column loads. The analysis uses PLAXIS 3D software, and the validity of the parametric study is examined through the results of centrifuge model tests conducted by the authors. The study shows that the concentrated pile arrangement method can help to considerably reduce the total and differential settlements as well as the induced bending moments of the raft. Moreover, the effects of parameters, such as pile length, pile number, raft thickness and load types, on the piled raft behavior are investigated. This study can help practicing engineers choose pile and raft parameters in combination with the concentrated pile arrangement method to produce an economical design.     

弹簧钢球式安全离合器在钻机中的应用

分析了钻机在过程中经常发生机械事故的主要原因,提出了解决这一问题的方法,即在钻机内的传动轴上安装弹簧钢球式安全离合器在钻机中的经过反复试验论证辽一方法的可行性。     

研究底板突水的结构力学方法

介绍了研究底板突水的结构力学方法，并用极限弯矩的理论计算得出确定底板隔水层有效厚度之计算公式。     

Predicting bending failure of CDM columns under embankment loading

The mechanism of bending failure and the magnitude of the bending moment in a column formed by cement deep mixing (CDM) under an embankment load were investigated by a series of three-dimensional (3D) finite element analyses. Based on the numerical results, a design method to consider the bending failure of the CDM column has been established. The usefulness of the proposed methods was verified using the results of two centrifuge model tests of the embankments on the CDM column improved soft model ground model reported in the literature, and the columns had tensile cracks or showed complete failure.     

用扭剪试验成果求剪切模量的计算公式

土的剪切模量是土工计算重要参数之一，通常是用弹性模量与们松比间接求得。本文结合扭转翼板仪的工作原理及其边界条件，推出用扭转力矩M和扭转剪切角θ直接求取剪切模量的计算公式。     

HY-1A卫星COCTS数据条带消除的两种定量化方法比较

HY-1A卫星是中国第一颗海洋遥感卫星,水色水温扫描仪(COCTS)是其主要探测器。由于各探测单元的信号响应特性不同,导致COCTS数据含有大量条带噪声。这严重影响了图像的质量和可视性,对资料的定量化应用也是十分不利的。为了解决这个问题,本研究采用矩匹配及直方图匹配法,对COCTS数据进行条带消除。结果表明,两种方法都是有效的,能够在消除条带的同时保持数据原有的物理意义,并避免细节特征的丢失。但是从整体效果看,直方图匹配法更好一些。本研究的结果同样适用于其他以并扫方式获取数据的遥感器的条带消除。