Azimuthal impact directions from oblique impact crater morphology

Planetary impact craters have a high degree of radial symmetry. This hampers efforts to identify the azimuthal impact direction for most craters – the radially symmetric component of an impact crater swamps any asymmetries that may be present. We demonstrate how the asymmetric component can be isolated and the direction of the asymmetries quantified using a two-dimensional eigenfunction expansion over a circular domain. The complex coefficients of expansion describe the magnitude and phase (angular alignment) of each term. From the analysis of hypervelocity impact craters formed in the laboratory, with impact angles ranging from 0° to 50° from the surface normal, we show that asymmetries which reveal the impact direction are still present at just 10° from the surface normal, and that the phase of one complex coefficient of expansion, c ₁₁, indicates the impact direction. Analysis of the lunar crater Hadley shows bilateral symmetry in the radially asymmetric component, which may be due to oblique impact. The 31-km lunar ray crater Kepler has morphological features that indicate the azimuthal impact direction. Coefficient c ₁₁ gives an azimuthal impact direction similar to that expected from the morphology, although post-impact gravitational collapse and slumping obscure the result to some degree. Ray craters may provide a means of testing the method for smaller 'simple' craters when data are available.     

Active and laboratory experiments in space plasma physics

This report focuses on active experiments in space as well as laboratory experiments which are directly related to space phenomena. The active experiments involve particle releases in the CRESS and AMPTE missions. Unexpected results such as the motion of the plasma triggered several interesting computer simulations and a laboratory experiment which will be reviewed. Critical Ionization Phenomena will be discussed in this context. A recent release over Arecibo was used to create a plasma lens to focus radiation from the HF heater beam. The higher power triggered several nonlinear processes. Advances in plasma sources and diagnostics have made it possible to scale many laboratory experiments. Discussed here are experiments on Alfvén waves generated by a localized source, 3D magnetic field line reconnection, three dimensional magnetized double layers and simulations of a tethered satellite.     

A methodology to determine thermal conductivity of soils from flux measurement

Determination of thermal properties of soils (viz., thermal resistivity, thermal conductivity, thermal diffusivity and heat capacity), which primarily influence heat migration through the soil mass, is essential in situations where geomaterials are relentlessly subjected to higher temperatures and temperature variations. These properties of the soil mainly depend upon its type, mineralogy, particle size and gradational characteristics, density and water content. In this context, earlier researchers have determined thermal conductivity of soils by employing a thermal probe (a line heat source), which works on the principle of transient method (TM) of heat conduction. However, this methodology cannot be employed for establishing the heat flow (read thermal regime) through the soil. Hence, development of an alternate technique, which facilitates quantification of temporal and spatial variation of the heat flux and temperature in the soil mass, becomes essential. With this in mind, a methodology to determine thermal conductivity of soils by employing the concept of thermal flux measurement (TFM) has been developed and its details are presented in this paper. Results obtained from the TM and TFM have also been critically evaluated for the sake of validation and generating more confidence in the proposed methodology.     

荧光猝灭法溶解氧传感器实验室校准方法研究

针对我国目前缺乏荧光猝灭法光学溶解氧传感器校准方法的现状,以AADI 4330F溶解氧传感器为实验对象,提出了一种适用于所有荧光猝灭法光学溶解氧传感器的实验室校准方法.该方法使用一个能够精确控制水体温度的自制校准装置,通过改变通入容器的氧气和氮气比例来控制容器内的溶解氧含量,在4个温度下分别测定至少10组水体温度值、传感器相位值和Winkler碘量法测定值数据,使用回归分析进行多项式拟合获取传感器校准系数.经过实验室验证,在校准试验温度范围内随机温度和溶解氧浓度下,使用该方法校准后传感器测定值与标准值偏差在±5 μmol/L以内,达到了仪器自身的准确度水平.本方法在校准结果准确度和温度适用范围等方面都明显优于两点校正法,表明该方法具有良好的校准效果和推广应用价值.     

Numerical and Experimental Study of the 3D Effect on Connecting Arm of Vertical Axis Tidal Current Turbine

Vertical axis tidal current turbine is a promising device to extract energy from ocean current. One of the important components of the turbine is the connecting arm, which can bring about a significant effect on the pressure distribution along the span of the turbine blade, herein we call it 3D effect. However, so far the effect is rarely reported in the research, moreover, in numerical simulation. In the present study, a 3D numerical model of the turbine with the connecting arm was developed by using FLUENT software compiling the UDF (User Defined Function) command. The simulation results show that the pressure distribution along the span of blade with the connecting arm model is significantly different from those without the connecting arm. To facilitate the validation of numerical model, the laboratory experiment has been carried out by using three different types of NACA aerofoil connecting arm and circle section connecting arm. And results show that the turbine with NACA0012 connecting arm has the best start-up performance which is 0.346 m/s and the peak point of power conversion coefficient is around 0.33. A further study has been performed and a conclusion is drawn that the aerofoil and thickness of connecting arm are the most important factors on the power conversion coefficient of the vertical axis tidal current turbine.     

旧金山湾卤虫在同安盐田实验池中种群动态的初步分析

美国旧金山湾卤虫于1989年引入同安盐田实验池养殖,1989年10月至1990年3月池内人工养殖卤虫的结果表明,秋、冬两季实验池的水温变化不是影响卤虫种群数量变动的主要原因,卤水盐度的变化对卤虫幼体群体数量有较大的影响,饵料是影响卤虫种群变动的主要因子,使用花生渣饼磨浆后投喂卤虫比使用干鸡粪更有利于卤虫种群的增长。实验证实旧金山湾卤虫能在同安盐田安全越冬.     

水面油膜微波辐射特性实验室测量与分析

要实现利用微波辐射计对海面溢油的厚度等参数进行遥感监测，必须先对水面油膜的微波辐射特性进行研究，以便为传感器的设计和遥感资料的解译提供依据。在实验室条件下，利用“灰体室”的环境条件及测量方法，测试了原油、燃料油和食用植物油膜的微波发射率与油膜厚度之间的关系，并对测量结果进行分析和讨论。为实际应用提供技术资料。     

Laboratory Observations on Internal Solitary Wave Evolution over A Submarine Ridge

Laboratory experiments were conducted in a wave flume on internal solitary wave （ISW） of depression and elevation types propagating over a submarine ridge in semicircular/triangular shape. Tests were arranged in series for combinations of submarine ridges of different heights and ISW of different amplitudes. The resuhant wave motions were found differing from thee of surface gravity waves. In deeper water, where an ISW of depression-type prevailed, the process of wave breaking displayed downward motion with continuous eddy on the front face of the ridge followed by upward motion towards the apex of the obstacle. Experimental results also suggested that blockage parameter ξ could be applied to classify various degrees of ISW-ridge interaction, i.e., ξ 〈 0.5 for weak interaction, 0.5 〈 ξ 〈 0.7 for moderate interaction, and 0.7 〈 ξ for wave breaking.     

Determination of Shaft Capacity for Pile under Cyclic Axial Loading in Clay

For load-controlled and displacement-controlled test data of piles cyclically axially loaded in clay, the displacement conditions are suggested for determining the shaft capacity. According to the suggested displacement conditions, not only the results of shaft capacity from laboratory model piles are close to those from in-situ piles, but also the results of load-controlled tests are in satisfactory agreement with those of displacement-controlled tests. Moreover, based on the test data of laboratory model piles in combination with the test data published, the paper suggests the values of the normalized shaft capacity of piles under a variety of static and cyclic loading combinations.     

WOCE CTD校准标准和我国的WOCE CTD校准实验室

对温度、电导率和压力等物理变量的定义、单位，传感器的实验室校准标准和我国在九五863项目中建立的WOCE水平的CTD校准实验室进行了介绍。